JPS60143574A - Evaluation method of semiconductor photo electrochemical electrode and its equipment - Google Patents

Abstract

PURPOSE:To accurately and quickly evaluate a semiconductor photo electrochemical electrode by using temperature increase value of a solar cell caused by a specified condition of irradiation light, and a potential of semiconductor electrode to a reference electrode. CONSTITUTION:Electrolyte is put into a sample chamber 2, and a reference electrode 31 and a counter electrode 32 are immersed in electrolyte with a semiconductor electrode 1 to be evaluated. The potential of the semiconductor 1 is varied in accordance with a program prepared by setting the potential of the semiconductor electrode 1 to the reference electrode, and light having a specified wavelength is intermittently irradiated to the electrode 1 in a specified way when voltage is applied to the electrode 1 and a circuit of the electrode 1 is opened. Temperature increase of the electrode 1 is directly detected, and quantum efficiency of the electrode 1 is calculated by using temperature increase value of the electrode 1 in a voltage applied condition, temperature increase value of a solar cell in a circuit opened condition, and a potential of the electrode 1 to the reference electrode 31 in a voltage applied condition. Thereby, a semiconductor photo electrochemical electrode is accurately and quickly evaluated.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a semiconductor photoelectrode, such as a photoelectrochemical type photovoltaic cell, which converts light energy into electrical energy or chemical energy represented by hydrogen by using a photoelectrochemical reaction. The present invention relates to a method and apparatus for evaluating the characteristics of a semiconductor photoelectrochemical electrode used in a reaction device, and in particular to a method and apparatus for measuring the quantum efficiency and/or energy conversion efficiency of a semiconductor photoelectrochemical electrode.

11 [1] In recent years, emphasis has been placed on the use of solar energy as an energy alternative to petroleum. Electrochemical photovoltaic cells, which utilize the same reaction to extract chemical energy such as hydrogen, are attracting attention. When converting light energy into electrical energy or chemical energy using this electrochemical photocell, it is necessary to select a semiconductor with high quantum efficiency and energy conversion efficiency as the electrode in order to use the light effectively. Measuring these efficiencies is extremely important in electrode development research.

By the way, the conventional method for measuring the quantum efficiency of semiconductor photoelectrochemical electrodes is to measure the number of incident photons using a photometer and calculate it from that value and the photocurrent value obtained from the photoelectrode reaction. However, in this case there were the following problems. In other words, in the above method, the number of incident photons measured by the photometer is calculated assuming that they are all absorbed by the electrode surface, but in cases where the electrode area is small or in the case of a semiconductor with large reflection on the electrode surface, A considerable amount of light may not be absorbed by the electrode, thus causing a considerable error between the number of photons actually absorbed by the semiconductor electrode,
Accurate quantum efficiency measurement becomes difficult. Furthermore, when using an optical photometer such as the Feriogizarate, it is effective when the wavelength of the irradiated light is 250 to 500 rv, but cannot be used at long wavelengths. The number of incident photons must be calculated indirectly from the light intensity ratio, which results in a problem of large measurement errors.

Moreover, optical light meters are not very easy to operate and require a considerable amount of measurement time when the light intensity is low.

As described above, the conventional quantum efficiency measurement method has various problems in accurately calculating the number of incident photons, and the obtained suspension efficiency also has a large error and is not easy to measure.

Purpose of the invention This invention was made in view of the above circumstances, and
The basic objective is to provide a new evaluation method and device that are completely different from conventional evaluation methods and devices for semiconductor photoelectrochemical electrodes.

This invention is based on the photothermal spectroscopy (PTS), which was separately invented by the present inventors.
The purpose of the present invention is to provide a novel method and apparatus for evaluating semiconductor photoelectrochemical electrodes using alS spectroscopy.

Conventionally, the absorbance measurement method, which measures the transmittance of light and calculates its reciprocal absorbance, has been widely known as a spectroscopic method using light to measure the absorption spectra of various substances. Photoacoustic spectroscopy has been developed to measure absorbance using acoustic effects. In response, the present inventors have developed a photothermal spectroscopy method that should also be referred to as a new third spectroscopy method. This photothermal spectroscopy involves irradiating a sample with light of different wavelengths and directly detecting the temperature rise value of the sample relative to the wavelength of the irradiated light using a highly sensitive thermosensitive element such as a thermistor placed in contact with the sample. It measures the spectrum of temperature rise of a sample in response to irradiation light.

As a result of examining 11 applications of the photothermal spectroscopy described above, the present inventors found that the quantum efficiency and energy conversion efficiency of semiconductor photoelectrochemical electrodes can be accurately and quickly measured by using the photothermal spectroscopy technique. They discovered this and came up with this invention.

In other words, since the energy that is not used as electrical energy or chemical energy in the semiconductor electrode that absorbs light will be released as heat, we predict that information regarding efficiency can be obtained by measuring the temperature of the semiconductor surface. As a result of repeated experimental studies, the inventors discovered that quantum efficiency and energy conversion efficiency can actually be obtained, leading to the creation of this invention.

Therefore, an object of the present invention is to provide a method and apparatus for evaluating semiconductor photoelectrochemical electrodes that can accurately and quickly evaluate semiconductor photoelectrochemical electrodes, and that are not complicated and easy to handle. do.

In order to achieve the above-mentioned objectives, the semiconductor electrode evaluation method and apparatus of the present invention have the following configuration.

That is, in the semiconductor photochemical electrode evaluation method of the first invention, an electrolytic solution is contained in a sample chamber that is thermally isolated from the surroundings, and a reference electrode and a counter electrode are immersed together with the semiconductor electrode to be evaluated in the electrolytic solution. Light of a selected wavelength is applied to the semiconductor electrode in a state in which a voltage is applied to the semiconductor electrode by increasing the potential with respect to the reference electrode according to a preset program, and in a state in which the semiconductor electrode is made an open circuit. The temperature rise of the semiconductor electrode due to the irradiation light is directly detected by intermittent irradiation as described above, and the temperature rise value of the semiconductor electrode due to the irradiation light in a voltage applied state and the temperature rise value of the solar cell due to the irradiation light in an open circuit state is measured. This method is characterized in that the quantum efficiency and/or energy conversion efficiency of the semiconductor electrode is determined using the potential of the semiconductor electrode with respect to a reference electrode in a voltage applied state.

Here, the specific way to measure quantum efficiency is as follows. That is, the temperature rise value of the semiconductor electrode due to the irradiation light detected while changing the applied potential in the voltage application state is normalized by the temperature rise value due to the irradiation light of the semiconductor electrode in the open circuit state,
Create a graph with the value obtained by multiplying each standardized concentration increase value by the energy determined by the wavelength of the irradiated light on the vertical axis and the potential obtained by subtracting the band potential from graph 1 from the potential applied to the semiconductor electrode on the horizontal axis. Then, each point within the charge flow saturation region on the graph is approximated by a straight line, and the slope of the straight line is used as the quantum efficiency of the semiconductor N pole.

On the other hand, the specific method for determining energy conversion efficiency is as follows. That is, the electrode reaction heat is corrected for the value obtained by extrapolating the approximate straight line on the graph created in the same manner as above, and the heat generated by non-radiative deactivation and recombination is calculated, and that value is used for irradiation. The energy conversion efficiency of the semiconductor electrode is determined by subtracting it from the total energy of the incident light determined by the wavelength of the light, the intensity of the irradiated light, and the irradiation time, and dividing the subtracted value by the total energy.

Note that the above-mentioned linear approximation is performed, for example, by the method of least squares.

Furthermore, the semiconductor photoelectrochemical electrode evaluation device of the second invention comprises: a sample chamber containing an electrolyte that is thermally isolated from the surroundings; and a semiconductor electrode to be evaluated that is immersed in the electrolyte in the sample chamber. a reference electrode and a counter electrode, and the semiconductor fit
! means for applying a voltage between i+ and a counter electrode such that the potential of the semiconductor electrode relative to the reference electrode changes according to a preset program; irradiation means for irradiating light with a wavelength of light; temperature detection means for directly detecting the temperature rise of the semiconductor electrode due to the irradiation light; and memory for storing and calculating the detection signal from the temperature detection means and the potential of the semiconductor electrode with respect to a standard electrode. arithmetic means; the storage arithmetic means is configured to calculate a value of the temperature rise of the semiconductor electrode due to the irradiation light, which is detected by the temperature detection means when the semiconductor electrode is in an open circuit state; The quantum efficiency and/or It is characterized by being designed to increase energy conversion efficiency.

Here, the storage/arithmetic means stores a temperature increase value of the semiconductor electrode due to the irradiation light detected by the temperature detection means by changing the applied potential in the voltage application state, and a temperature rise value of the semiconductor electrode detected by the temperature detection means in the open circuit state. The temperature rise value caused by the irradiation light is stored, and each temperature rise value in the stored voltage application state is normalized by the stored temperature rise value in the open circuit state, and each of the normalized temperature rise values is The value multiplied by the energy determined by the wavelength of the irradiated light is stored as a function of the potential obtained by subtracting the furan 1 to band potential from the potential applied to the semiconductor electrode, and the multivalues in the light current saturation region of that function are expressed as a straight line. The approximation is made, and the slope of the straight line is calculated to output data as the quantum efficiency of the semiconductor electrode.

Further, the memory calculation means similarly stores the temperature rise value of the semiconductor electrode due to the irradiation light detected by the temperature detection means by changing the applied potential in the voltage application state, and the temperature increase value detected by the temperature detection means in the open circuit state. The temperature rise value of the semiconductor electrode due to the irradiation light is stored, and each temperature rise value in the stored voltage application state is normalized by the stored temperature rise value in the open circuit state, and each of the normalized temperatures is The value obtained by multiplying the increase value by the energy determined by the wavelength of the irradiated light is stored as a function of the potential obtained by subtracting the flat band potential from the potential applied to the semiconductor electrode, and the multivalues in the charge flow saturation region of that function are plotted as a straight line. After approximating, and then extrapolating the approximation straight line, the electrode reaction heat is corrected and calculated to calculate the heat generated by non-radiative decoupling and recombination. It is subtracted from the total energy of incident light determined by time, the subtracted value is calculated by 1j by the total energy, and data is output as the energy conversion efficiency of the semiconductor electrode.

Furthermore, the irradiation light means includes a light source, a wavelength selector for selecting light of a wavelength to be irradiated onto the semiconductor electrode from the light from the light source, and an irradiation light intermittent means for intermittent the irradiation light to the semiconductor electrode. It is said to be configured with the following.

Here, the wavelength selector is composed of a spectroscope having a dispersion element that separates light from a light source, or a plurality of bandpass filters each having a different wavelength band.

The irradiation light intermittent means includes a light interrupter (so-called shutter), a drive means for inserting and removing the light interrupter into and out of the optical path of the irradiation light to the semiconductor electrode, and a control unit for controlling the drive means. The optical circuit breaker is configured such that its opening timing is IQtiO based on the result of processing and determining the output signal of the temperature detecting means, and its cutting timing is set at a preset opening time.

Further, the irradiation light intermittent means includes an optical interrupter, a driving means for inserting and removing the optical interrupter into and out of the optical path of the irradiating light to the semiconductor electrode, and a control section for controlling the driving means. $1' The lid section is equipped with a timer for setting the opening time and cut-off time of the optical interrupter.

Alternatively, the irradiation light intermittent means may include an optical interrupter (so-called chopper) in which a light transmitting part and a light shielding part are alternately formed, a driving means for driving the optical interrupter, and a control section for controlling the driving means. The irradiation/interruption time is controlled by controlling the driving speed of the optical interrupter at a preset speed.

On the other hand, the temperature detection means is composed of two heat-sensitive elements having substantially the same characteristics within the measurement range, and a circuit for detecting the difference in output between the heat-sensitive elements, and one heat-sensitive element detects the temperature of the semiconductor electrode. The other heat-sensitive element is placed in contact with the semiconductor electrode for direct detection, and the other heat-sensitive element is placed near the semiconductor electrode to detect the temperature of the electrolyte around the semiconductor electrode. By doing so, it is configured to detect a temperature rise only in the semiconductor electrode, which eliminates the influence of ambient temperature changes.

Here, the output difference detection circuit is constituted by a DC bridge or an AC bridge incorporating the same heat-sensitive element.

EXAMPLES Hereinafter, examples of the semiconductor photochemical electrode evaluation method and evaluation device W of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the apparatus used in the semiconductor photochemical electrode evaluation method of the present invention, that is, an embodiment of the second invention. A reference electrode 31 and a counter electrode 32 made of a saturated calomel electrode or the like are immersed in the electrolytic solution together with the semiconductor electrode 1 to be evaluated. A potential applying section 33 is connected to these electrodes 1, 31, 32 via an opening/closing means 34 such as a switch.

This potential applying section 33 applies a voltage between the semiconductor electrode 1 and the counter electrode 3220- so that the potential of the semiconductor electrode 1 with respect to the reference electrode 31 changes according to a preset program, and performs data processing to be described later. - It is configured so that the potential of the semiconductor electrode 1 is controlled by a signal from the control section 27C of the control section 27. Note that the potential application section 3
3 has a built-in current detection means (not shown), and the current value 1 flowing through the semiconductor electrode 1 detected by this current detection means and the potential V of the semiconductor electrode 1 with respect to the reference electrode 31 are stored in the data processing/control unit 27. It is sent to the calculation section 27A.

In the illustrated example, the sample chamber 2 has an inner wall 2A made of a heat insulating material.
Consisting of a double wall with the outer wall 2B made of insulation material as well,
The space between the inner wall 2A and the outer wall 2B is filled with liquid 3 to provide better heat insulation, but a single wall may be used depending on the case. A condenser lens 3 for condensing the irradiated light toward the semiconductor electrode is provided on one surface of the outer wall 2B of the sample chamber 2, and a condenser lens 3 is provided on the inner wall 2A at a position corresponding to the condenser lens 3. A transparent window 4 is provided. Therefore, irradiation light from outside the sample chamber is irradiated onto the semiconductor electrode 1 via the condenser lens 3 and the transmission window 4. Note that when the light source is a laser beam, a condensing lens is not necessary.

A high-sensitivity heat-sensitive element 5, such as a thermistor, for detecting the temperature of the semiconductor electrode 1 is directly attached to the semiconductor electrode 1, and a heat-sensitive element 5 for the semiconductor electrode is installed near the semiconductor electrode 1. A reference heat-sensitive element 6 made of a high-sensitivity heat-sensitive element such as a thermistor having substantially the same characteristics as the reference heat-sensitive element 6 is arranged. The latter heat-sensitive element 6 is a semiconductor electric [
The sensor electrode 11 is provided to detect a temperature rise of the semiconductor electrode 11 by eliminating the influence of the electrolyte temperature around the electrode 1 on measurement errors. Note that it is desirable that each of the heat-sensitive cables 5.6 be disposed at a position where no direct irradiation light is incident thereon.

Furthermore, a semiconductor electrode 1 is inserted into the sample chamber 2 from a condenser lens 3.
A half mirror 7 is disposed as necessary near the irradiation optical path leading to the irradiation light path. This half mirror 7 has a light 18 which will be described later.
In order to calibrate the wavelength distribution of the light source 8 and eliminate measurement errors caused by variations in intensity depending on the wavelength of the light source 8 (in other words, to standardize the output data), a part of the irradiated light is transferred to the sample chamber 2 as necessary. The position in the irradiation optical path (i.e., the position where part of the irradiation light is reflected to the carbon black 9 )
and a position separated from the irradiation optical path (that is, a position where a part of the irradiation light is not reflected to the carbon black 9). A standard heat-sensitive element 10, such as a thermistor, having substantially the same characteristics as each of the above-mentioned heat-sensitive elements 5.6 is also attached to the carbon black 9 at a position that does not directly receive irradiation light. Incidentally, during normal measurement without calibrating the wavelength distribution of the light source 8 as described above, the half mirror 6 is kept out of the irradiation optical path.

The light source 8 is composed of a high-intensity light source, such as a xenon light source, and a filter 123-1 for cutting unnecessary infrared light from the light source 8 and a condensing lens 12 are mounted on the front side thereof. They are arranged in order. Furthermore, the condenser lens 12 and the condenser lens 3 on the sample chamber 2 side
On the optical path between the A chopper 16 as an optical interrupter and a spectrometer 1 as a wavelength selector
7 are provided in that order.

The shutter 14 is connected to a driving means 18 such as a motor for opening and closing the optical path by inserting and removing the shutter into and out of the optical path, and the shutter driving means 18 includes a driving circuit for driving and controlling the shutter. It is electrically connected to 19.

On the other hand, in the chopper 16, a range forming a predetermined angle with respect to the center of rotation is cut out to serve as a light transmitting part, and the remaining angular range is used as a light shielding part. The structure is such that the optical path is repeatedly opened and closed. A chopper drive means 20 such as a motor is connected to the chopper 16, and a drive circuit 21 for driving and controlling the chopper drive means 24-20 is electrically connected. For Chopper 16,
A synchronization signal generator 22 is attached to output a signal synchronized with the opening and closing of the optical path by the chopper 16.

In the above example, the first irradiation light intermittent means 13 consisting of the shutter 14 etc. and the second irradiation light intermittent means 15 consisting of the chopper 16 etc. are both installed, but in reality both are installed. It is not necessary to install them, and only one of them may be installed.

The spectroscope 17 is for selecting the wavelength of the irradiation light to be irradiated from the light source 8 to the semiconductor 'Ntii1,
A wavelength selection driver 23 is attached to rotate the dispersion element 17A such as a diffraction grating to change the selected wavelength. Note that the wavelength selector is constructed of a plurality of bandpass filters each having a different wavelength band instead of the spectroscope 17, and by replacing the filter through which the light from the light source 8 should pass, the light irradiated onto the semiconductor electrode 1 can be changed. The configuration may be such that the wavelength of the wavelength is selected. In this case, a plurality of filters can be attached to a rotating disk, for example, and the wavelength of the light irradiated to the semiconductor electrode 1 can be changed by rotating the rotating disk using a wavelength selection driver such as a motor. .

In some cases, a single wavelength laser light source or a variable wavelength laser light source may be used as the light 1 [18] instead of the high-intensity light source, and in that case, a wavelength selector such as the spectrometer 17 can be omitted.

The semiconductor electrode heat-sensitive element 5 and the reference heat-sensitive element 6 are connected to an output difference detection circuit 40 that detects the output difference between them. This output difference detection circuit 40 is only for detecting the temperature rise value of the semiconductor electrode 1, which removes the influence of the surrounding electrolyte temperature.
The oscillator 25 is composed of an AC bridge 24 having a 10kHz AC signal, for example, for driving the AC bridge 24.

The output of this AC bridge 24 is sent to a synchronization detection circuit 26. This synchronous detection circuit 26 is for synchronous rectification (synchronous detection) of the output of the AC bridge 24 in synchronization with the AC signal of the oscillator 25, and therefore the synchronous detection circuit 26
The output level 6 corresponds to the temperature rise value of the semiconductor electrode 1 after correcting the ambient temperature. The output of this synchronization detection circuit 26 is sent to a data processing/control section 27.

Here, when the chopper 16 is used as the irradiation light intermittent means, the synchronization detection circuit 26 detects the difference between the AC signal for driving the AC bridge 24 and the synchronization signal of the chopper 16 (signal generated by the synchronization signal generator 22). Double synchronous detection synchronized with two types of signals is used.

In the above example, the output difference detection circuit 40 is connected to the AC bridge 2.
4, but it is of course possible to use a DC bridge depending on the case.

Furthermore, as mentioned above, the standard carbon black 9 installed as needed is also configured to detect the temperature rise value of the carbon black itself, which has been removed from the influence of the temperature of the surrounding electrolyte. That is, the standard 27-thermal element 10 attached to the carbon black 9 is also connected to the output difference detection circuit 40, and the output difference detection circuit 40 is used to detect the output of the semiconductor electrode heat-sensitive element 5 and the reference heat-sensitive element 6. It can be configured with a double bridge that combines a bridge for detecting a difference and a bridge for detecting an output difference between the standard heat-sensitive element 10 and the reference heat-sensitive element 6. Further, depending on the case, one end of a single bridge may be configured to be switched between the semiconductor N-electrode heat-sensitive element 5 and the reference heat-sensitive element 10.

In the above example, a heat-sensitive element for detecting the temperature of the electrolyte around the standard carbon black 9 is commonly used as a means for detecting the temperature of the electrolyte around the standard carbon black 9, but in some cases, a different heat-sensitive element may be used. The element may be placed in the electrolyte near the carbon black 9.

The data processing/control unit 27 includes a storage and calculation unit 27A that stores and calculates the potential V of the semiconductor electrode 1 from the potential application unit 33 and the output of the electric F&I and the synchronization detection circuit 26 (temperature rise value of the semiconductor!1i1). and its memory calculation unit 27
The display section 27B shows the data obtained in Table 28-A, and the potential of the semiconductor electrode 1 by the potential application section 33 and the shutter drive circuit according to a preset program and signals from the storage and calculation section 27A. 19, a control section 27C that controls the operation of the chopper drive circuit 21 and the like.

Regarding the control of the shutter drive circuit 19, for example, the 111111 section 27C is used as a determination circuit that processes and determines a signal corresponding to the temperature rise value of the semiconductor electrode itself output from the synchronization detection circuit 26, and a determination circuit that processes and determines the signal corresponding to the temperature rise value of the semiconductor electrode itself output from the synchronization detection circuit 26, and It has a configuration that includes a timer for setting the time, and outputs a shutter opening command signal based on the result of processing and determining the temperature rise value signal, and also outputs a shutter closing command signal when the opening time set in the timer has elapsed. Just let it happen. Specifically, the determination circuit that processes and determines the semiconductor electrode temperature increase value signal as described above is configured by a circuit that differentiates the concentration increase value and a circuit that compares and determines the differential value with a reference level. If the differential value of the value is a negative value (that is, when the temperature increase value is decreasing), the shutter opening command signal should be output when the absolute value of the differential value becomes below a certain level. Good.

Alternatively, regarding the control of the shutter drive circuit, the control unit 27C is configured to include a timer for setting the shutoff time of the shutter 14 and a timer for setting the open time of the shutter 14, and when the set shutoff time has elapsed, The shutter opening command signal may be output, and the shutter shutoff command signal may be output when a set opening time has elapsed.

On the other hand, regarding the control of the chopper drive circuit 21, the control section 27G is configured to include chopper rotation speed control means for controlling the rotation speed of the chopper 16 to a preset speed, and by controlling the rotation speed of the chopper 16,
The configuration may be such that the irradiation time and cut-off time of the irradiation light are determined according to 6.

Further, the reference electrode 3 of the semiconductor electrode ii by the potential applying section 33
Regarding the control of the potential with respect to 1, for example, the control section 27C
However, the configuration may be such that the potential change command signal is output in synchronization with the opening command signal or the shutoff command signal of the shutter 14 according to a preset program. That is, when the shutoff time or opening time of the shutter 14 has elapsed for the time set in advance on the timer, or when the differential value of the temperature rise value is reached, li! It is sufficient to output a potential change command signal when the potential becomes less than I. Alternatively, a signal synchronized with the operation of the chopper 16 from the synchronization signal generator 22 of the chopper 16 may be accepted, and the potential change command signal may be output in synchronization with the interruption or opening of the optical path by the chopper 16.

FIG. 2 shows a specific example of the AC bridge 24 used in the output difference detection circuit 40 for detecting the output difference between the semiconductor electrode heat-sensitive element 5 and the reference heat-sensitive element 6. In FIG. 2, the operational amplifier 28 operates as a working amplifier of an AC bridge, and the operational amplifier 29 operates as a bandpass filter at the oscillation frequency of the oscillator 25, for example, 10k)1z.

Next, the semiconductor electrode is evaluated using the above-mentioned device. The overall operation of the device when performing this will be explained.

The heat-sensitive element 5 is attached to the semiconductor electrode 1 to be measured in advance, and the semiconductor electrode 1, the reference electrode 31 and the counter electrode 32 are
1, and the electrodes 1, 31, and 32 are immersed in the electrolytic solution in the sample chamber 2. The wavelength of the light to be irradiated is set by a wavelength selector such as the spectroscope 17 or a bandpass filter. In addition, at the time of the first measurement, the opening/closing means 34 is opened to keep the semiconductor electrode 1 in an open circuit.

Then, when the optical path is opened by the shutter 14 or the chopper 16, the semiconductor electrode 1 is irradiated with light of the above wavelength, and the energy absorbed by the semiconductor electrode 1 out of the energy of the irradiated light becomes heat in an open circuit state. The temperature of semiconductor electrode 1 increases. The temperature of this semiconductor electrode 1 is detected by a heat sensitive element 5. On the other hand, the temperature of the electrolyte around the semiconductor electrode 1 also rises, and the ambient temperature is detected by the heat sensitive element 6. The temperature difference between the two is detected by the output difference detection circuit 23, and a signal corresponding to the temperature obtained by subtracting the ambient temperature from the temperature 32 of the semiconductor electrode 1, that is, the temperature increase value of only the semiconductor electrode 1 corrected for the ambient temperature, is generated. The signal is output from the synchronization detection circuit 26 and sent to the data processing/&III section 27.

When the irradiation time to the semiconductor electrode 1 reaches the opening time of the shutter 14 preset by the timer, or when the light transmission time determined by the rotation speed of the chopper 16 is reached, the optical path of the irradiation light to the semiconductor electrode 1 is changed to the shutter 14. Or it is blocked by the shielding part of the chopper 16. Although the temperature of the semiconductor electrode 1 rapidly decreases due to this optical path interruption, the ambient temperature hardly decreases. However, since the ambient temperature is corrected as described above, data processing and
The control unit 27 is given a temperature increase value due to the irradiation light of the semiconductor electrode 1 itself, which has removed the influence of the temperature of the surrounding electrolyte.

FIG. 3 shows the waveform of the temperature change of the semiconductor electrode 1 measured in this way with respect to time. In FIG. 3, the broken line A indicates the semiconductor electrode 1 when no correction is made for the ambient concentration.
The broken line B shows the change in ambient temperature, and the straight line C shows the temperature change of the semiconductor electrode 1 corrected for the ambient temperature, that is, the output waveform of the synchronization detection circuit 26.

The output waveform C of this synchronization detection circuit 26 and the maximum temperature rise value (ΔTOO in FIG. 3) during each irradiation period are
The temperature rise value in the open circuit state is stored in the storage/calculation section 2.
7B.

On the other hand, in a state in which the opening/closing means 34 is closed, that is, in a state in which the potential application unit 33 is connected to the semiconductor electrode 1 and a potential is applied, light having the same wavelength as that in the measurement in the open circuit state described above is irradiated to the semiconductor electrode. At the same time as measuring the six temperature rise values, the current i of the semiconductor electrode 1 is measured, and these measured values and the potential V of the semiconductor electrode 1 with respect to the reference electrode are stored in the storage/calculation section 27B. In this case, the potential V of the semiconductor electrode 1 with respect to the reference electrode 31 is determined according to a preset program.
are sequentially changed, and the temperature rise value .DELTA., current i of the semiconductor electrode 1 is measured at each potential, and these are stored in correspondence with each potential V. Note that the measurement of the temperature increase value at each potential is corrected for the temperature of the surrounding electrolytic solution, as in the case described above. With the potential applying section 33 connected in this manner, a portion of the absorbed energy becomes electrical energy or chemical energy, and the remaining energy becomes heat, causing the temperature of the semiconductor electrode to rise.

After the measurement at a certain potential is completed and the optical path is cut off, the timing at which irradiation for the next measurement at a different potential is started is determined by the timer settings as described above in the case of the shutter 14. - or by the differential value of the temperature increase being less than or equal to a certain value, and if the chopper 16 is used, it is determined by the rotation speed of the chopper 16. In any case, the timing at which irradiation is started again after the optical path is interrupted is the timing at which the semiconductor electrode 1
The temperature is set or controlled so that the temperature of the ambient temperature drops sufficiently to become almost the same as the ambient temperature.

Of course, depending on the situation, measurement at a certain potential may be repeated two or more times. In the actual measurement, shutter 1
Either the shutter 14 or the chopper 16 may be used, but normally the shutter 14 is used when the response speed of the heat sensitive element is slow, and the chopper 16 is used when the response speed is sufficiently fast.

In this way, measurements are sequentially made at specific potentials,
Finally, the measurement in the entire measurement potential region is completed.

Note that the above-mentioned measurements can be performed at various different wavelengths, but in that case, it is desirable to normalize the measured value of the semiconductor electrode temperature rise value by the measured value of the heat-sensitive element 10 of the standard carbon black 9. . That is, since the light source 8 has wavelength characteristics and the intensity differs depending on the wavelength, in order to perform an absolute evaluation of the characteristics of the semiconductor electrode 1,
It is desirable to eliminate the influence of the wavelength characteristics of the light source 8. In the above-mentioned apparatus, the half mirror 7 is inserted into the light path to guide the irradiated light to the carbon black 9, and the temperature increase value is measured for each wavelength in the entire measurement wavelength range by the heat sensitive element 10. The specific measurement method in this case is Semiconductor Electric I! ii
This is similar to the measurement for .

The temperature rise value of the semiconductor electrode 1 is normalized by dividing the temperature rise value of the semiconductor electrode 1 by the temperature rise value of the carbon black 9 obtained in this way at each 36-wavelength. The measurement of the Naori-bon black 9 can be performed simultaneously with the measurement of the semiconductor electrode 1 when the half mirror 7 is provided as described above, and in such a simultaneous measurement, the measurement of the semiconductor electrode 1 The value can be normalized on the spot, but of course, the measurement of carbon black 9 should be performed separately from the measurement of semiconductor electrode 1, and the measured value should be stored and used when measuring the semiconductor electrode 1. The measured value of the semiconductor electrode 1 may be normalized by reading out. In the latter case, half mirror 7
An ordinary mirror can be used instead.

Next, the principle of calculating the quantum efficiency and energy conversion efficiency of a semiconductor electrode using each measurement value as described above will be explained.

If a semiconductor electrode is irradiated with light of a certain wavelength, the irradiation energy will be a value determined according to the wavelength, that is, E < e
V/1) hoton). Here, if the semiconductor electrode is irradiated with light of that wavelength for 1 second and the intensity of the light absorbed by the semiconductor electrode is T (photon/sea), the total energy obtained by the semiconductor electrode is Eft...
1) It is expressed as

In an open circuit, all of the light energy irradiated to the semiconductor electrode 1 becomes heat (provided that no fluorescence or phosphorescence is generated), so the heat q0 generated in an open circuit is calculated using the following formula: % Formula % (2) −5 Standard for semiconductor electrode 1! Heat q generated when #A31 is irradiated with the same light as above with potential V applied
is expressed by the following formula.

q=Qsc+TΔS+e77it −(3) where Qs
o is the heat generated by non-radiative deactivation or recombination, TΔS is the heat associated with the entropy change of the electrode reaction (usually referred to as electrochemical Peltier heat), and ev+1 is the heat due to polarization. However, η is the potential V of the semiconductor electrode and the graph] Band potential Vfb
, i.e., η-V-Vfb (4), and i is the current flowing through the semiconductor electrode 1 (number of electrons/
5ec), and e is for aligning the dimensions by charge. Note that Qsc and TΔ51ey+it are all expressed in ev.

Since the heat transfer coefficient of the semiconductor electrode in an open circuit and the heat transfer coefficient of the semiconductor electrode in a state where potential (2) is applied are equal, the following equation holds true.

△Tq △Toe qo ... (5) However, in equation 5, ΔTo is the temperature change due to the irradiation light of the semiconductor electrode in the state where a potential is applied, and ΔToc is the temperature change due to the irradiation light of the semiconductor electrode in an open circuit state. .

Therefore, the following equation is derived from equations (2), (3), (4), and (5).

E・ΔT/ΔTOO− (6) Here, the quantum efficiency q of the semiconductor electrode 1 can be set as nq=i/I (7) 39− in the saturated charge current region, so from (6) , E・ΔT/ΔToc=(Qsc+TΔS),/It+enq(V−Vfb
)...(8) becomes. This equation (8) shows the relationship between the temperature change due to the irradiation light of the semiconductor electrode and the potential in the saturated charge current region.

In equation (8), the first term on the right side is a value that is independent of potential, the second term is a term for heat due to polarization, and E - ΔT / ΔTOC and V - V fb are slopes nq (this is quantum efficiency) shows a linear relationship. Therefore, as shown in graph A in Figure 4, the horizontal axis shows V -V fb, and the vertical axis shows E・ΔT/ΔTO.
If C is plotted and equation (8) is graphed, the slope corresponds to 114, and the quantum efficiency can be determined by calculating the slope.

On the other hand, from equation (8), the point of V = V fl), that is, the intercept obtained by extrapolating the linear plot of E·ΔT/ΔToe−V−Vfb corresponds to (Qsc+TΔS)/Tt.

Here, the light intensity (1) and the irradiation time (2) are known, and the heat TΔS40- associated with the entropy change of the electrode reaction can be considered separately, but is generally negligible. Therefore, by these (Q sc + TΔS)
Qsc can be adjusted by correcting the value of /It.

The energy conversion efficiency in the photoelectrode reaction is determined by the amount of energy ((
3) The heat Q generated by non-radiative deactivation and recombination excluding the heat eη1t due to polarization and the electrode reaction heat TΔS from the heat q according to the formula
Since it means the proportion occupied by the energy of sc, the energy conversion efficiency np is expressed as follows.

np(%) −(E It −QSC) /E It
X 100...(9) Therefore, in equation (9), Qsc obtained as described above
By substituting , since E, I, and t are known, the energy conversion efficiency np can be calculated.

The fifth section describes a specific flow for actually determining the quantum efficiency and energy conversion efficiency of semiconductor electrodes according to the principles described above.
As shown in the figure.

In FIG. 5, if the wavelength of the light irradiated to the semiconductor electrode is selected by the irradiation means, the irradiation energy E (ev
/photon) is determined. The value of energy E corresponding to this wavelength is stored in advance in the storage/enhancing unit 27A or other appropriate memory, and the value of E corresponding to the wavelength is automatically read out by selecting the wavelength. Then, the temperature rise value ΔTOC of the semiconductor electrode when the semiconductor electrode is irradiated with light of the wavelength in an open circuit state is measured and the value is stored. In addition, we measured the temperature rise of six semiconductor electrodes when the semiconductor electrode was irradiated with light of the same wavelength while applying a potential, while changing the potential ■ sequentially. The current i is measured, and ΔT and I at each potential (2) are stored together with the value of the potential (2). It goes without saying that it is desirable to store the temperature rise value of the semiconductor electrode itself as the temperature rise value ΔT1ΔToe after correction for the ambient temperature as described above.

Next, divide the temperature rise value ΔT in the potential applied state by the temperature rise value ΔToe in the open circuit state to obtain ΔT/ΔToc, and multiply this by the energy E of the irradiation light to obtain E・ΔT/ΔT.
Turn on oc. It goes without saying that this calculation is performed for each potential V value. On the other hand, from each potential ■, a flat band potential Vf determined depending on the type of semiconductor electrode
The value of Vfb is calculated by subtracting b.

Then, the vertical axis y is E・ΔT/ΔToc, and the horizontal axis
-v rbt, -c, V-Vfb-E ・ΔT/ΔT
Convert oc into a function, draw a graph A, and calculate each point of the graph A (
That is, each measurement point corresponding to each potential is stored, and a linear approximation is performed to each stored point by the method of least squares.

Note that the linear approximation of graph A is performed for measurement points within the charge flow saturation region. That is, by storing the current i flowing at each potential ■, v −v rb
Graph B in FIG. 4 is created by plotting 1 against 1, and a linear approximation of graph A is performed for the saturated region of I in graph B. And the slope of the obtained straight line y=ax
I put it on. Since this slope a corresponds to the quantum efficiency nq as is clear from the equation (8), this value is recorded and displayed as the quantum efficiency.

43--5 Regarding energy efficiency, the value of the extrapolated intercept on the approximate straight line of graph A obtained as described above, that is, E・ΔT/Δl”oc at V −V fb=O
Calculate the value of , multiply it by It, subtract electrode reaction heat TΔS, and calculate Qsc. And the above (9)
By calculating according to the formula, the energy conversion efficiency n
p is determined and its value is recorded and displayed.

Although the electrode reaction heat TΔS can be measured separately as described above, it is generally a value that can be ignored for most substances. Therefore, in general, TΔS is set to zero and Qs
c correction calculation can be performed.

Below, the results of actual measurements made by the present inventors on semiconductor electrodes will be described.

In Figure 6, a CdS single crystal is used as a semiconductor electrode, a platinum electrode is used as a counter electrode, and a saturation force (0) (lumi electrode) is used as a reference electrode.
The photocurrent and temperature change of a Cds single crystal electrode due to light irradiation at various potentials in an electrolytic solution containing 0.2 mol of Na2804 as a supporting electrolyte and KaFe(CN)a as a supporting electrolyte are shown. Here, the wavelength of the irradiated light is 340
nl, and the time for one irradiation was 20 seconds. Note that in FIG. 6, ON indicates the start of irradiation, and OFF indicates light interruption. Moreover, the temperature in FIG. 6 is after correction based on the ambient temperature.

As shown in Fig. 6, a decrease in temperature change was observed when the potential V was −0.75 VO compared to the temperature change in an open circuit, but when the potential was changed to +1.0 VO It and + 3.0 V
It is clear that as the concentration increases, the anode polarization progresses and the concentration increase increases.

In FIG. 7, the temperature rise value ΔT and photocurrent 1 at each potential obtained as described above are plotted against the electrode potential V. As shown in FIG. 7, a decrease in the temperature rise value ΔT was observed as the photocurrent began to flow. This means that recombination and separation of electrons and holes generated by photoexcitation occur competitively. In the region where photoelectricity Wt1 was saturated, a linear increase in temperature increase value ΔT was observed.

The temperature rise value in the same circuit is shown by a broken line.

Furthermore, in Fig. 8, there is a [cd
About semiconductor electrodes made of S single crystal! The temperature rise value ΔT and the photocurrent 1 were measured by changing the potential in a Na2SO3-based electrolytic solution containing the base material sO3, and E・ΔT/ΔTo
The results of changing c and 1 to v-vr and bron 1 are shown. Note that the wavelength of the irradiated light is 340nIIl, so E is 3. (i eV.

The slope of the E·ΔT/ΔToe~v−vr plot in FIG. 8 in the charge flow saturation region is 1.00, and therefore the quantum efficiency nq of the photoelectrode reaction in this case was estimated to be 1.00.

Figure 9 shows E・ΔT/ΔTO when the irradiation time was varied in the range of 5 to 60 seconds under the same measurement conditions as in Figure 8.
C~v -v rb Represents the slope of a straight line plot. It is clear that changing the irradiation time does not change the slope, so the length of the irradiation time has no effect on determining the quantum efficiency.

In FIG. 10, the same E・ΔT/
The results of examining the slope of the T 00 to V − V fb linear plot are shown. From this result, it is clear that the slope does not change even if the light intensity is changed, and therefore the intensity of the light intensity does not affect the determination of quantum efficiency.

Further, FIG. 11 shows a CdS single crystal semiconductor electrode 1 in the presence of SO3 as a reducing agent as in the case of FIG. : Lai T, irradiation light wavelength 490ni, 400 nm.

E・ at each wavelength when changed to 340n-
ΔT/ΔToc-v-vrb plot is shown. E・ΔT/ΔToc expressed in eV as the wavelength becomes shorter
Although the value of is small, the slope of the straight line is 1.
00, so the quantum efficiency is
It is clear that it is constant at 1.00.

Table 1 shows the quantum efficiency nq determined by the method of the present invention for various semiconductor electrodes. For comparison, Table 1 also shows the number of incident photons measured by a chemical photometer and the quantum efficiency nq- calculated from the photocurrent value obtained at that time.

47- As is clear from Table 1, Cd 51Cd Se 1T
For i 02 and ZnO, m was determined by both methods.
The child efficiencies nq, , nq' are almost the same. However, in MO82, Ga As, Ga P, etc.
The value nq' obtained by the actinometer is much smaller than 1 inq obtained by the method of the present invention. This difference is thought to be due to reflection and scattering on the electrode surface. Therefore, the present inventors determined the surface reflectance R at an incident angle of 45° for a semiconductor electrode with a large difference between nq and nq', calculated the amount of light absorbed by the electrode from this reflectance, and calculated the chemical tip. The quantum efficiency nq- obtained by was corrected. The corrected quantum efficiency nq'' is shown in Table 2.

As is clear from Table 2, the quantum efficiency n q I corrected for the value obtained by the chemiphotometer is quite close to the value of the quantum efficiency n q obtained by the method of the invention.

Figure 12 shows E・ΔT/△ during the photoelectrode reaction of a CdS single crystal semiconductor electrode in an electrolytic solution containing Fe(ON)a.
This is 48- by plotting TOC~V-V fb. Here, the wavelength of the irradiated light is 490 nm.

The photoelectrode reaction in this case is Fe (CN)e +P-+Fe (CN)e,
Therefore, the electrode reaction heat TΔS becomes an endothermic reaction. With an oxidation current equal to the saturation photocurrent value observed at this time,
Constant current electrolysis was performed using an AL+ electrode in an electrolytic solution containing Fe (CN)a, and the resulting temperature change at the AU/electrolyte interface was detected with a thermistor. This temperature change and the surface temperature change observed in the open circuit of the CdS electrode (
Assuming that the electrode reaction heat can be expressed in Ov by comparing the respective magnitudes of 2 and 5 eV), in this case Fe (CN)e → Fe (CN
) It was found that the electrode reaction heat bar of a + e corresponds to 0.4 eV. Therefore, E・ΔT in Figure 12
/ΔTOC~v −v rb straight line plot upwards 0
．． The one shifted by 4θV is the corrected E of TΔS/l
−△T / △T oc −V −V fb(D rl
It is considered that it represents the A coefficient, and the value of the extrapolation point of v − v rb in this corrected straight line plot,
That is, the value of Qsc/lt was 1.4 eV.

From the results, it was found that the energy conversion efficiency np was 44%.

Figure 13 shows the E in the presence of various reducing agents when a ZnO polycrystalline electrode is irradiated with monochromatic light of 3400 nm.
- Shows the relationship of ΔT/ΔT00-V.

The temperature increase value differed depending on the type of reducing agent, and the slope of the linear plot of E·ΔT/ΔToe−V, that is, the quantum efficiency, was 0.90 in all cases except for S.

Then, from the data in Figure 12, we calculated the Qsc value when each reducing agent was used, and when the irradiation light wavelength was 340 nm, E was 3.6.
If there is an eV, then Korokara ((3,6-Qsc) / 3.
6) The energy conversion efficiency Op when using each reducing agent is calculated by x 100 (%) and is shown in Table 3.

On the other hand, if the flat band potential of the semiconductor is E fb and the reduction potential of the reducing agent is Er, the maximum obtainable open-circuit photovoltaic force VIlla× is equal to the bending of the band, and Vmax
Since it is given by = l Efb-Er l, the maximum energy efficiency that can be obtained c
, t (l Efb-E+' l / 3.6) X
It becomes 100 (%). This value was calculated using a needle bar for each reducing agent and is also shown in Table 3 as "1p'.

It is clear from Table 3 that the maximum energy efficiency "lip" obtained by the above-mentioned method and the energy conversion efficiency rip determined by the method of the present invention are close to each other.

nq-: Child efficiency 3:l crystal due to chemical light placement 51- 53- 52- Effects of the Invention According to the semiconductor electrode evaluation method and device of the present invention, quantitative values of irradiated light, such as differences in intensity and characteristics, etc. It is possible to accurately determine the quantum efficiency and/or energy conversion efficiency of a semiconductor electrode used in a photoelectrochemical device regardless of the It can produce effects such as being relatively simple and cost-reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a semiconductor electrode evaluation device of the present invention, FIG. 2 is a wiring diagram showing an example of an AC bridge as an output difference detection circuit used in the device of FIG. 1, and FIG. A waveform diagram showing changes in the detected temperature of the semiconductor electrode, FIG. 4 is E-ΔT/ΔT oC-V -V in the method of this invention.
rh7 Lotto J: A graph showing the hI~v-vrb plot, FIG. 5 shows the semiconductor 1! Energy conversion efficiency np and quantum efficiency n of III
A flowchart showing a specific flow for calculating q, FIG. 6 is a diagram showing changes over time in photocurrent 1 and electrode temperature when changing the applied electrode for a CdS single crystal semiconductor electrode, and FIG.
The figure shows the same <Temperature rise value ΔT for CdS single crystal electrode
and a diagram showing the relationship between photocurrent i and potential V, Figure 8 is the same <E・ΔT/ΔTOC for CdS single crystal electrode ~
Figure 9 shows the E・ΔT/ΔTOC~V-Vfb straight line when changing the irradiation time for a CdS single crystal electrode. Diagram showing the relationship between plot slope and irradiation time, No. 10
The figure shows the relationship between the slope of the same linear plot and the light intensity when the light intensity is changed for a ZnO polycrystalline electrode, and Figure 11 shows the relationship between the slope of the linear plot and the light intensity when the light intensity is changed for a CdS single crystal electrode. E・ΔT/ΔTOC at wavelength
〜V-vfb plot, Figure 12 shows the E・Δ of the CdS single crystal electrode when determining the energy conversion efficiency.
A diagram showing the T/ΔTOO-V-Vfb plot, Figure 13 shows E・ΔT/ΔT0c for each reducing agent when the reducing agent in the electrolyte is changed for ZnO polycrystalline semiconductor.
-V plot. DESCRIPTION OF SYMBOLS 1... Semiconductor electrode, 2... Sample chamber, 5... Heat sensitive element for semiconductor electrode, 6... Heat sensitive element for reference,
8...Light source, 9...Carbon black, 10.
... Standard thermal element, 13... First irradiation light intermittent means, 14... Shutter (light interrupter), 15...
- Second irradiation light intermittent means, 16... chopper (light interrupter), 17... spectrometer as a wavelength selector, 1
7A... Dispersion element, 24... AC bridge, 2
6... Period detection circuit, 27... Data processing/control unit, 27Δ... Memory calculation unit, 31... Reference electrode, 32... Counter electrode, 33... Potential application unit, 34.
...Opening/closing means, 40...Output difference detection circuit. Applicant HIa Ken Akimoto - JASCO Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (one idiot)

Claims (1)

[Claims] <1) An electrolytic solution is contained in a sample chamber that is thermally isolated from the surroundings, and a reference electrode and a counter electrode are immersed together with a semiconductor electrode to be evaluated in the electrolytic solution, and the semiconductor electrode is , in a state in which a voltage is applied by changing the potential with respect to a reference electrode according to a preset program, and in a state in which the semiconductor electrode is open circuited, light of a selected wavelength is intermittently applied to the semiconductor electrode in a predetermined manner. The temperature rise of the semiconductor electrode due to the irradiation light is directly detected, and the temperature rise value of the semiconductor electrode due to the irradiation light in a voltage applied state, the temperature rise value of the semiconductor electrode due to the irradiation light in an open circuit state, and the voltage 1. A method for evaluating a semiconductor photoelectrochemical electrode, the method comprising measuring the quantum efficiency and/or energy conversion efficiency of a semiconductor electrode using the potential of the semiconductor electrode relative to a reference electrode in an applied state. (2) The temperature rise of the semiconductor electrode due to the irradiation light detected by changing the applied potential in the voltage application state is normalized by the temperature rise value of the semiconductor electrode due to the irradiation light in the open circuit state,
Then, create a graph with the value obtained by multiplying each standardized temperature rise value by the energy determined by the wavelength of the irradiated light on the vertical axis and the potential obtained by subtracting the flat band potential from the potential applied to the semiconductor electrode on the horizontal axis, A semiconductor photoelectrochemical electrode according to claim 1, wherein each point within the photocurrent saturation region on the graph is approximated by a straight line, and the quantum efficiency of the semiconductor electrode is determined based on the slope of the straight line. evaluation method. (3) The method for evaluating a semiconductor photoelectrochemical electrode according to claim 2, wherein each point within the photocurrent saturation region on the graph is linearly approximated by the least squares method to determine its slope. (4) Normalize the temperature rise due to the irradiation light of the semiconductor electrode detected by changing the applied potential in the voltage application state by the temperature rise value due to the irradiation light of the semiconductor electrode in the open circuit state,
Then, create a graph with the value obtained by multiplying each standardized temperature increase value by the energy determined by the wavelength of the irradiated light on the vertical axis and the potential obtained by subtracting the flat band potential from the potential applied to the semiconductor electrode on the horizontal axis, Each point in the charge flow saturation region on the graph is approximated by a straight line, and the electrode reaction heat is corrected for the value obtained by extrapolating the approximated straight line to estimate the heat generated by nonradiative deactivation and recombination. , subtract that value from the total energy of light incident on the semiconductor electrode determined by the wavelength of irradiation light, irradiation time, and intensity of irradiation light, and divide the subtracted value by the total energy to calculate the energy conversion efficiency of the semiconductor electrode. A method for evaluating a semiconductor photoelectrochemical electrode according to claim 1, characterized in that: (5) a sample chamber containing an electrolyte that is thermally isolated from the surroundings; a reference electrode and a counter electrode that are immersed in the electrolyte in the sample chamber together with the semiconductor electrode to be evaluated; means for applying a voltage such that the potential of the semiconductor electrode relative to the reference electrode changes according to a preset program, and light of a selected wavelength applied to the semiconductor electrode immersed in the electrolyte in said sample chamber. irradiation means for irradiating the semiconductor electrode, temperature detection means for directly detecting the temperature rise of the semiconductor electrode due to the irradiation light, and storage and calculation means for storing and calculating the detection signal from the temperature detection means and the potential of the semiconductor electrode with respect to a standard electrode. The storage calculation means is configured to store a temperature rise value of the semiconductor electrode due to irradiation light detected by the temperature detection means when the semiconductor electrode is in an open circuit state, and a temperature rise value of the semiconductor electrode with respect to a reference electrode when a voltage is applied. The quantum efficiency and/or energy conversion efficiency of the semiconductor electrode is determined by storing and calculating the temperature rise value of the semiconductor electrode caused by the irradiation light and the potential of the semiconductor electrode detected by the temperature detecting means corresponding to the electric potential. A semiconductor photochemical electrode evaluation device characterized by: (6) The storage/arithmetic means is configured to detect a temperature rise value of the semiconductor electrode due to the irradiation light detected by the temperature detection means by changing the applied potential in the voltage application state, and a temperature increase value detected by the temperature detection means in the open circuit state. The temperature rise value of the semiconductor electrode caused by the irradiation light is stored, and each temperature rise value in the stored voltage application state is normalized by the stored temperature rise value in the open circuit state, and each of the normalized temperature rise values is The value obtained by multiplying the temperature rise value by the energy determined by the wavelength of the irradiated light is stored as a function of the potential obtained by subtracting the flat band potential from the potential applied to the semiconductor electrode, and the multivalues in the charge flow saturation region of that function are plotted as a straight line. 6. The device for evaluating a semiconductor photoelectrochemical electrode according to claim 5, wherein the slope of the straight line is calculated and output as data as m-molecular efficiency of the semiconductor electrode. (7) The storage/calculation means is configured to store a temperature rise value of the semiconductor electrode due to the irradiation light detected by the temperature detection means by changing the applied potential in a voltage applied state, and a temperature rise value of the semiconductor electrode detected by the concentration detection means in an open circuit state. The temperature rise value due to the irradiation light is stored, and each temperature rise value in the stored voltage application state is normalized by the stored temperature rise value in the open circuit state, and each of the normalized temperatures is The value obtained by multiplying the increase value by the energy determined by the wavelength of the irradiated light is stored as a function of the potential obtained by subtracting the flat band potential from the potential applied to the semiconductor electrode, and the multivalues in the charge flow saturation region of that function are plotted as a straight line. The heat generated by non-radiative deactivation and recombination is calculated by correcting the electrode reaction heat with respect to the value obtained by extrapolating the approximate straight line, and the value is calculated based on the wavelength of the irradiation light, the irradiation time,
Subtracted from the total incident light energy determined by the irradiation light intensity,
6. The semiconductor photoelectrochemical electrode evaluation device according to claim 5, wherein the subtracted value is divided by the total energy and data is output as the energy conversion efficiency of the semiconductor electrode. (8) The irradiation light means includes a light source, a wavelength selector for selecting light of a wavelength to be irradiated to the semiconductor electrode from light from the light source, and an irradiation light intermittent for intermittent irradiation light to the semiconductor electrode. 6. A semiconductor photoelectrochemical electrode evaluation device according to claim 5, which is configured to include means. (9) The wavelength selector is comprised of a spectroscope having a dispersion element that separates light from a light source, or a plurality of bandpass filters each having a different wavelength band. Semiconductor photoelectrochemical electrode evaluation device. (10) The irradiation light intermittent means includes a light interrupter and its light source.
The optical circuit breaker is composed of a driving means for inserting and removing the S-interrupter into and out of the optical path of the irradiation light to the semiconductor electrode, and a control section for controlling the driving means, and the opening timing of the optical circuit breaker is determined by the temperature detecting means. 9. The semiconductor photoelectrochemical electrode evaluation device according to claim 8, wherein the semiconductor photoelectrochemical electrode evaluation device is controlled based on a result of processing and determining the output signal of the device, and is configured such that the timing of shutoff is set at a preset opening time. (11) The irradiation light intermittent means includes a light interrupter, a drive means for inserting and removing the light interrupter into and out of the optical path of the irradiation light to the semiconductor electrode, and a control means for controlling the drive means. 9. The semiconductor photoelectrochemical electrode evaluation device according to claim 8, wherein the semiconductor photoelectrochemical electrode evaluation device is configured such that the open time and cut-off time of the optical interrupter are controlled by a timer provided in the control means. (12) The irradiation light intermittent means includes a light interrupter in which a light transmitting part and a light shielding part are formed alternately, a driving means for driving the optical interrupter, and a control part for controlling the driving means. The semiconductor photoelectrochemical 'R' pole evaluation according to claim 8, wherein the irradiation/interruption time is controlled by controlling the driving speed of the optical interrupter at a preset speed. Device. (13) The temperature detection means is constituted by two heat-sensitive elements having substantially the same characteristics within the measurement range and a circuit for detecting the difference in output of the heat-sensitive elements, one of the heat-sensitive elements being a semiconductor electrode. The other heat-sensitive element is placed in contact with the semiconductor electrode to directly detect the temperature, and the other heat-sensitive element is placed near the semiconductor electrode to detect the temperature of the electrolyte surrounding the semiconductor electrode, and the difference in the output of the heat-sensitive element is detected. 6. The semiconductor photoelectrochemical electrode evaluation device according to claim 5, wherein the semiconductor photoelectrochemical electrode evaluation device is configured to detect the temperature rise of only the semiconductor electrode, thereby eliminating the influence of changes in the surrounding ocean. (14) The semiconductor photoelectrochemical electrode evaluation device according to claim 13, wherein the output difference detection circuit is constituted by a DC bridge or an AC bridge incorporating the thermosensitive element.