CN111884588A - Method for measuring interface state of silicon-based specific photovoltaic device - Google Patents
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- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
- H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a method for measuring interface state of a silicon-based specific photovoltaic device, which can accurately evaluate the interface state density of the silicon-based heterojunction photovoltaic device, wherein a passivation tunneling medium of the device to be measured is ultrathin quasi-insulating SiOxA layer with a thickness of less than or equal to 2.0nm and containing a small amount of metal elements therein. The interface state density of a heterojunction device with a thicker oxide and silicon nitride insulating layer is generally measured by adopting a deep energy level transient state spectrum method, but the interface layer is ultrathin quasi-insulating SiOxIn the case of a layer, the conventional methods such as DLTS are prone to generate a capacitance overflow phenomenon under a slightly high forward bias, and it is difficult to obtain an interface state signal. Therefore, aiming at the particularity of the electronic structure of the interface region of the heterojunction device, the invention adopts a high-frequency light injection mode not lower than 1.0MHz to measure the C-V characteristics of the device under dark and illumination, combines a diode capacitance approximation and a numerical calculation model, extracts information related to the interface state from the two C-V curves, and indirectly measures to obtain the interface state density of the heterojunction device.
Description
Technical Field
The invention relates to a method for measuring interface state density of a heterojunction solar cell, in particular to a photovoltaic device which is provided with an ultrathin silicon oxide layer and contains a small amount of metal elements in an amorphous silicon oxide layer, and is applied to the technical fields of preparation technology of high-efficiency crystalline silicon solar cells and silicon oxide thin film composite material science.
Background
Sqss (Semiconductor quantum-Insulator) heterojunction solar cells originated in the last 60 th century and were extensively studied for their advantages of simple structure, low cost, and high conversion efficiency. ITO/a-SiO using ITO film as hole selection layerxthe/Si heterojunction device has been studied since 40 years ago. In 1976, J.B.Dubow et al deposited an ITO film on p-Si by ion beam sputtering, and the devices achieved 12% conversion efficiency under AM1.0 illumination, they had proposed the assumption that ultra-thin silicon oxide was present at the ITO/p-Si interface. Between 70 and 80 years of the last century, the J.Shewchun research group theoretically and experimentally studied the carrier transport mechanism of SQIS cells, and proposed that when the thickness of an insulating layer is below 2nm, photogenerated carriers can be transported from p-Si to ITO due to tunneling effect, and ITO thin film is deposited by ion beam sputtering to obtain ITO/SiO2The conversion efficiency of the cell with the p-Si structure was 12.8%. After a decade of silence, ITO/n-Si structure devices have been studied again, however the conversion efficiency is still around 12%. In 2012, doctor du huiwei directly deposited ITO film on n-Si treated with hydrofluoric acid solution by radio frequency magnetron sputtering technique, introduced into textured surface and back electric field, and formed SQIS (ITO/SiO) with In and Sn metal elements In silicon oxide layerxThe conversion efficiency of the/n-Si) heterojunction device is 11.5%, and meanwhile, the work function difference between the ITO thin film and the Si is proposed to be the direct power of the built-in electric field formed by the device. Therefore, most of the research on ITO/Si is about process optimization and device principles, but an effective method for evaluating the interface state of the device is not clearly provided. Considering that the interface state is an inherent property of the heterojunction device and the particularity of the interface layer in the SQIS device, including its thickness less than 2nm and SiOxThe layer contains metal elements. Therefore, it is crucial to establish a convenient, reliable and applicable interface state measurement mode. To pairOn Si/SiO2In the research of the interface, there are also many methods for measuring the interface state, such as a high and low frequency capacitance method, a conductance method, and DLTS (Deep Level transient spectroscopy), the method can easily measure the interface state of the device with thicker insulating layers of silicon oxide, aluminum oxide, silicon nitride and the like, the distribution of the interface state of the insulating layers is U-shaped, the bottom of a conduction band and the top of a valence band are provided with higher band tail states, the middle and the vicinity of a forbidden band are provided with low band tail states, however, the measurement of the interface state density of the SQIS device is difficult to realize, because the interface layer is too thin and contains a small amount of metal elements, under the condition of slightly high positive bias, the phenomenon of capacitance overflow is easy to generate, which means that the differential capacitance value far exceeds the range and tends to infinity, so that signals such as an effective deep energy level and an interface state of an interface layer of the SQIS device are difficult to obtain by conventional methods such as DLTS and the like, and the signals refer to a defect state of crystalline silicon near the center of a forbidden band. Therefore, how to reasonably evaluate the SQIS heterojunction solar cell and the technical problem of improving the performance of the photovoltaic device in device optimization are urgently needed to be solved.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art, and provides a method for measuring the interface state of a silicon-based specific photovoltaic device, which can measure the interface state of an SQIS heterojunction solar cell, and is combined with a radio frequency magnetron sputtering deposition ITO film process, a thermal evaporation metal electrode process and a capacitance-voltage test system to establish a set of method capable of measuring the interface state of the heterojunction device with an ultrathin silicon oxide layer, so that the operation process is optimized, and the derivation process and the calculation process are simple and clear.
In order to achieve the purpose, the invention adopts the following technical scheme:
the method for measuring the interface state of the silicon-based specific photovoltaic device is used for measuring the interface state of a heterojunction device with an ultrathin silicon oxide layer, wherein the heterojunction device with the ultrathin silicon oxide layer is a hole selection type ITO/SiOx(In)/n-Si heterojunction photovoltaic devices In which ITO/SiOxUltra-thin SiO In (In) laminated composite thin film materialsxThe (In) substance layer is formed between the ITO film and the n-Si substrate and contains In and Sn elementsAnd the thickness is not more than 2.0nm, a capacitance-voltage measurement system is utilized, and a light injection method is adopted to carry out hole selection type ITO/SiOxThe interface state density of the (In)/n-Si heterojunction photovoltaic device was measured.
As the preferred technical scheme of the invention, the ultrathin SiO film is made ofxThe (In) material layer contains Si2O、SiO、Si2O3And SiO2A series of compounds of different compositions, and the oxide SiO of siliconxContains ions and atomic states of In and Sn elements.
As the preferred technical scheme of the invention, the ultrathin SiO film is made ofxThe (In) substance layer contains In and Sn element negative ion state, and the negative ion is In SiOxAcceptor expansion state is introduced into the layer and is not local.
As the preferred technical scheme of the invention, the ultrathin SiO film is made ofxThe (In) material layer has a thickness of 1.0-2.0 nm. This thickness range facilitates the injection of light.
As a preferred technical scheme of the invention, the method adopts ITO/SiOxIn the (In)/n-Si laminated composite film, the thickness of the ITO film layer is 80nm and is used as a hole transport layer, and the thickness of the n-Si material layer is 120-140 mu m.
As the preferred technical proposal of the invention, the hole selection type ITO/SiO is processed by adopting a light injection modexThe interface state density of the (In)/n-Si heterojunction photovoltaic device is measured, and the interface state density is deduced from the obtained C-V curve.
As a preferred technical scheme of the invention, the applied voltage is less than the overflow voltage VTThe interface layer of the SQIS device is in a depletion layer state, and when the applied voltage is greater than the overflow voltage VTThe capacitance of the SQIS device tends to be infinite, and the phenomenon of overflow of the tunnel capacitance occurs.
As the preferred technical scheme of the invention, the C-V characteristics of the device under dark and illumination are measured by adopting a high-frequency light injection mode not lower than 1.0MHz, information related to the interface state is extracted from the two C-V curves by combining a diode capacitance approximation and a numerical calculation model, and the interface state density of the heterojunction device is obtained by indirect measurement.
As a preferred technical scheme of the invention, the method for measuring the interface state of the silicon-based specific photovoltaic device comprises the following steps:
a. introducing light injection into the SQIS heterojunction battery to be detected;
b. moving the SQIS heterojunction battery in the step a to an Agilent capacitance-voltage (C-V) test system, setting the frequency to be 1MHz and keeping the frequency unchanged, and ensuring that differential capacitance has response;
c. measuring the SQIS heterojunction device in the step b under illumination and darkness to obtain a corresponding C-V curve, wherein in the experiment, a direct current bias voltage applied to a front electrode of the device is swept from a depletion region to an accumulation region to change the width of the depletion region, and the scanning step length is 0.05V/s; when negative bias is applied, an inversion layer is formed on the silicon surface, the total capacitance change is very small due to the shielding effect of the cavity, the total capacitance changes rapidly until the bias is added to be more than 0V, and at the moment, the width of a depletion region changes rapidly under the influence of the applied bias; since the overflow voltage is related to the thickness of the interface region, the overflow voltage V isTMore than 2.0V, preferably setting the external bias voltage at-1.0V, and detecting the capacitance values under different bias voltages by using another signal which is a high-frequency detection signal;
d. C-V curves respectively obtained under the dark and light conditions in the step C are analyzed and processed, and when the C-V curves are processed, the C-V curves in the dark are translated to the left by a theoretical photoproduction voltage value to obtain C-V curves under ideal light; so as to combine the change of the image to deeply understand the meaning of the interface state density calculation formula;
e. and d, obtaining the information of the interface state density from the C-V curve under the ideal illumination obtained in the step d, and obtaining the interface state density through an interface state density calculation formula.
In the step c, the width of the depletion region in the light condition is influenced by the combined action of the photogenerated voltage and the direct current bias voltage, and the depletion region in the dark condition is only influenced by the applied bias voltage.
As a preferable technical scheme of the invention, in the step a, a tungsten filament bulb with power not lower than 20W is placed right above the SQIS heterojunction battery to be tested, and light injection is introduced.
As a preferable technical scheme of the invention, in the step a, the device area of the SQIS heterojunction battery to be tested is not more than 1cm2And the thickness is not more than 150 mu m.
The method for measuring the interface state density of the SQIS heterojunction device is based on the following principle:
the measuring method for measuring the interface state of the silicon-based specific photovoltaic device can measure the interface state density of the SQIS heterojunction device, and adopts advanced methods and ideas such as a semiconductor heterojunction photoelectric device theory and the like. The method for measuring interface state density in different ways has different principles, and for a special dielectric layer of an ultrathin quasi-insulating layer with the thickness less than or equal to 2.0nm and containing a small amount of metal elements, the metal elements in the insulating layer in the device are equivalent to a 'leak', a channel is formed similarly, the quasi-insulating layer can be punctured by a slightly high voltage, and therefore interface state signals of the device with the special dielectric cannot be obtained by the traditional methods such as a high-low frequency capacitance method, a deep energy level transient spectrum and the like. The principle of measuring the interface state of the special dielectric device is to accurately evaluate the density value of the average interface state by quantifying the influence of the interface state on the recombination of photogenerated carriers at the interface. The sqs device evolved from the MIS structure device only in whether the material of the upper layer was a semiconductor or a metal material, and the ITO thin film had excellent conductivity, which was regarded as a metalloid material, so the equivalent circuit of the sqs device was simulated using the MIS structure. First, the 1/C can be known according to the C-V curve in the dark2The relationship with bias voltage is obtained, so that the photogenerated voltage value V of the device is fittedD. When light is injected, photo-generated electrons and holes are separated by a built-in electric field in a depletion region and are transported to the positive and negative electrodes of the battery. According to an abrupt PN junction approximation formula, i.e. Wd＝[VD(2r 0)(NA+ND)/q(NAND)]1/2In which N isAAnd NDRespectively a doped acceptor concentration and a donor concentration,rand0respectively, the vacuum dielectric constant and the dielectric constant of silicon, VDQ is the elementary charge for the value of the photogenerated voltage, so that the depletion region width W can be calculatedd. Depletion region width WdAnd photo-generated voltage value VDIs a positive correlation. The total capacitance C is approximated by a parallel plate capacitor by the differential capacitancedIs in the relationship of C ═ WdIn which the dielectric constant is given. According to the differential capacitance definition of semiconductor knowledge, the total capacitance of the SQIS device is measured to be equal to the series connection of the depletion layer capacitance and the insulation layer capacitance, namely 1/Ci＝1/C(Si)+1/C(SiO2)，CiIs the total capacitance, C, of the SQIS device(Si)And C(SiO2)Respectively, the capacitance of silicon and the capacitance of amorphous silicon oxide. The total capacitance can be estimated by the width of the depletion region. The change in capacitance may reflect multiple factors associated with the depletion region, such as carrier recombination, etc. Under the dark condition, an inversion layer is formed at an interface due to the work function difference between the ITO film and the Si substrate, and meanwhile, a built-in electric field is formed, so that the energy band of the silicon surface is bent qV, and V is the potential difference of the energy band bending under the dark condition. When ideal light is injected, the photogenerated carriers are accumulated at the interface without considering any factor for recombining the photogenerated carriers, such as interface state, trap state, radiation damage and the like, and the bending of the energy band is reduced to q (V-V)D)，VDIs the photogenerated voltage under ideal illumination conditions. When the actual light injection is carried out, the influence of an interface state on the recombination of photo-generated carriers is considered, and the actual photo-generated voltage is lower than VDThe degree of band bending becomes q (V-V)S)，VSThe photogenerated voltage considering the influence of interface state under the actual light injection condition is less than V and VD. By comparing the photo-generated voltage value V under ideal conditionsDAnd the actually measured VSTherefore, the interface state density of the SQIS heterojunction device, namely D, can be quantitatively estimatedit＝(VD-VS)·Ci/EgQ, wherein EgIs the forbidden bandwidth of Si. In Si/SiOxThe negative influence on the device performance at the interface of (A) is reflected in DitThe above. The existence of the interface state directly influences the open-circuit voltage of the device, and the measurement of the interface state density of the device is beneficial to optimizing the deposition process and further optimizing the performance of the device.
Method for measuring interface state densityThe method has certain errors, including capacitance measurement, device area measurement and (V)D-VS) The measurement of (2). In order to reduce errors, the area of the measuring device is to ensure that the illumination intensity is kept constant and the light injection conditions are the same.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the method is suitable for the SQIS device with the ultrathin interface layer, and the metal elements are contained in the SQIS device, so that the blank of the interface state measuring method is filled;
2. the invention has better development prospect and has the advantages of popularization and application prospect, and the photoelectric conversion efficiency of the device prepared by the invention has larger scope of improvement from the aspects of device design principle, model numerical calculation and process optimization.
3. The method is simple, high in measurement accuracy and high in efficiency.
Drawings
FIG. 1 shows an example of an ITO/a-SiO film according to the present inventionxStructure of (In)/n-Si device and a-SiOxSchematic of atomic distribution In (In) layer.
FIG. 2 is a graph of the capacitance-voltage characteristics of SQIS prepared at different sputtering powers under dark conditions, and the inset is a graph of the capacitance-voltage characteristics of an SQIS device prepared at 85W in accordance with one embodiment of the present invention.
FIG. 3 is a diagram of SQIS total capacitance varying with depletion region width and applied bias voltage, respectively, according to an embodiment of the present invention, with an inset diagram showing an equivalent circuit model.
FIG. 4 shows an ITO/a-SiO film according to an embodiment of the present inventionxA composite influence graph of the interface state of the/n-Si device on photo-generated carriers; (a) darkness (b) ideal lighting; (c) actual illumination.
Fig. 5 is a schematic diagram of a capacitance-voltage characteristic result of a method for measuring an interface state according to an embodiment of the invention and a calculation formula. The illustration is 1/C2Linear dependence on bias voltage.
FIG. 6 is a graph showing the variation trend of interface state density, minority carrier lifetime and leakage current for ITO films of different thicknesses according to an embodiment of the present invention.
FIG. 7 shows an embodiment of the present inventionEXAMPLE II ITO/a-SiO prepared without sputtering PowerxAverage interface state density D of/n-Si deviceitGraph of variation with sputtering power.
FIG. 8 shows ITO/a-SiOxThe J-V curve of the/n-Si heterojunction device changes along with the sputtering power; (b) four parameters (V)oc、JscFF, η) as a function of the sputtering power.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
in the embodiment, referring to fig. 1 to 6, a method for measuring the interface state of a silicon-based specific photovoltaic device measures the interface state of a heterojunction device with an ultrathin silicon oxide layer, wherein the heterojunction device with the ultrathin silicon oxide layer is a hole-selective ITO/SiO layerx(In)/n-Si heterojunction photovoltaic devices In which ITO/SiOxUltra-thin SiO In (In) laminated composite thin film materialsxThe (In) material layer is formed between the ITO film and the n-Si substrate, contains In and Sn elements, and has a thickness of not more than 2.0nm, and is prepared by using a capacitance-voltage measurement system and a light injection methodxThe interface state density of the (In)/n-Si heterojunction photovoltaic device was measured. This embodiment is an ultra-thin a-SiOxITO/a-SiO of novel (In) materialsxMeasuring the interface state density of the interface layer of the (In)/n-Si device by adopting a light-assisted high-frequency C-V method; wherein, ITO/SiOxUltra-thin SiO In (In) laminated composite thin film materialsxThe layer is formed between the ITO thin film and the n-Si substrate.
In this example, a 20W tungsten bulb was placed directly above the device in order to introduce light injection. During the test, the light source was turned on until the end of the experiment to ensure continuous light injection.
In the present embodiment, a capacitance-voltage system of Agilent is used, and the frequency is set to 1 MHz.
This example uses thermal evaporation and magnetron sputtering techniques to deposit films of different thicknessesITO film, Observation of ITO/a-SiOxThe variation trend of the interface state density of the/n-Si structure device. FIG. 1 shows ITO/a-SiO of this examplexStructure diagram of/n-Si device and atom schematic diagram In amorphous silicon oxide layer, In which In-O-Si ternary compound is arranged In intermediate layer and indium element has certain concentration gradient, a-SiOx(i) The layer has no metal elements, and has good passivation effect. FIG. 2 shows the C-V characteristics under dark conditions and 1MHz of the SQIS heterojunction device with 80nm ITO film in this example, which indicates that the tunnel capacitance overflow phenomenon occurs near 3.0V bias. The rising of the SQIS capacitor is in the depletion region, when the external grid voltage is larger than VTAnd in the process, the far overrange of the high-frequency capacitor tends to be infinite, namely, the SQIS high-frequency capacitor cannot enter a multi-sub accumulation area, and the phenomenon of overflow of the tunnel capacitor occurs. FIG. 3 is an equivalent circuit diagram of the SQIS device of this embodiment, in which the total capacitance of the SQIS device is plotted as a function of the width of the depletion region, and solid squares correspond to the interface layer SiOx1.2nm and a solid triangle of 1.8 nm. The curve of the open circle is the variation of the total capacitance of the SQIS experimentally measured with the applied bias voltage. As can be seen from fig. 3, the experimental data is in good agreement with the results of the theoretical simulation. FIG. 4 is a schematic energy band diagram of the interface region of the SQIS device of this embodiment. FIG. 4(a) shows inversion of the silicon surface and band-up bending qV due to the work function difference between ITO and n-Si under dark conditions, and FIG. 4(b) shows band bending q (V-V) when photogenerated carriers accumulate on the silicon surface under ideal light conditions, without considering interface recombination and the likeD) FIG. 4(c) shows that under actual illumination, when only the recombination of photo-generated carriers caused by interface states is considered, the photo-generated voltage is lower than VDThe band bending is q (V-V)S). FIG. 5 is a schematic diagram of the photo-assisted high frequency C-V method of the present embodiment, which is illustrated as 1/C2The linear relationship with bias voltage, extrapolating the fitted photogenerated voltage, the shielding effect of the holes is minimal when a negative bias is applied, and the change in total capacitance affects the depletion region width when a positive bias is applied. FIG. 6 shows ITO/a-SiO films of different thickness deposited by this examplexThe change trends of the interface state density, the leakage current and the minority carrier lifetime of the/n-Si heterojunction solar cell for ITO thin films with different thicknesses show along with the ITO thin filmThe thickness is increased, and the density of interface state is reduced to 1.23 × 1011cm-2eV-1And no longer change, the better the interface passivation effect, and the better the squis cell performance.
Example two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in this example, ITO/a-SiO was observed mainly by changing the sputtering powerxThe change trend of the interface state density of the/n-Si structure device, and the material microstructure of the interface layer influences the performance of the device. FIG. 7 shows ITO/a-SiO of the present embodimentxInterface state density D of/n-Si deviceitWith the change trend graph of the sputtering power, the sputtering power is firstly reduced and then increased, the optimal sputtering power can be obtained, and the optimization of the device is facilitated. FIG. 8 shows ITO/a-SiO solid particles of this embodimentxAs can be seen from FIG. 8, a series of devices show good photovoltaic performance, and the best photovoltaic performance of the devices is shown in that when the sputtering power is 120W, the conversion efficiency reaches 9.63 percent and V percentoc＝0.45V、Jsc＝28.57mA/cm2FF ═ 71.2%. When the interface state density is lower, a device with the best photovoltaic performance is obtained, the principle of a semiconductor device is met, and optimization of the photovoltaic device is facilitated. The interface state density is a direct measure of the interface defects, can directly influence the open-circuit voltage of the photovoltaic device, and can be used for evaluating the performance of the device.
According to the embodiment, the method can accurately evaluate the interface state density of the silicon-based heterojunction photovoltaic device, and the passivation tunneling medium of the device to be tested is ultrathin quasi-insulation SiOxA layer with a thickness of less than or equal to 2.0nm and containing a small amount of metal elements therein. In general, Deep-Level Transient Spectroscopy (Deep-Level Transient Spectroscopy) is used to measure the interface state density of heterojunction devices with thicker insulating layers of silicon oxide, aluminum oxide and silicon nitride, but for ultra-thin quasi-insulating SiO on the interface layerxIn the case of a layer, the conventional methods such as DLTS are prone to generate a capacitance overflow phenomenon under a slightly high forward bias, and it is difficult to obtain an interface state signal. Thus, for the electronic structure of the interface region of the heterojunction deviceThe method adopts a high-frequency light injection mode not lower than 1.0MHz to measure the C-V characteristics of the device under dark and illumination, combines a diode capacitance approximation and a numerical calculation model, extracts information related to an interface state from the two C-V curves, and indirectly measures to obtain the interface state density of the heterojunction device.
While the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments, and various changes, modifications, substitutions, combinations or simplifications made according to the spirit and principles of the present invention should be replaced by equivalents, which are within the scope of the present invention as long as the invention is satisfied with the purpose of the present invention.
Claims (10)
1. A method for measuring the interface state of a silicon-based specific photovoltaic device is used for measuring the interface state of a heterojunction device with an ultrathin silicon oxide layer, and is characterized in that: the heterojunction device with the ultrathin silicon oxide layer is a hole selection type ITO/SiOx(In)/n-Si heterojunction photovoltaic devices In which ITO/SiOxUltra-thin SiO In (In) laminated composite thin film materialsxThe (In) material layer is formed between the ITO film and the n-Si substrate, contains In and Sn elements, and has a thickness of not more than 2.0nm, and is prepared by using a capacitance-voltage measurement system and a light injection methodxThe interface state density of the (In)/n-Si heterojunction photovoltaic device was measured.
2. The method of claim 1, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: ultrathin SiOxThe (In) material layer contains Si2O、SiO、Si2O3And SiO2A series of compounds of different compositions, and the oxide SiO of siliconxContains ions and atomic states of In and Sn elements.
3. Silicon-based special photovoltaic according to claim 1The method for measuring the interface state of the device is characterized by comprising the following steps: ultrathin SiOxThe (In) substance layer contains In and Sn element negative ion state, and the negative ion is In SiOxAcceptor expansion state is introduced into the layer and is not local.
4. The method of claim 1, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: ultrathin SiOxThe (In) material layer has a thickness of 1.0 to 2.0 nm.
5. The method for measuring the interface state of a heterojunction device with an ultra-thin silicon oxide layer as claimed in claim 1, wherein: on ITO/SiOxIn the (In)/n-Si laminated composite film, the thickness of the ITO film layer is 80nm and is used as a hole transport layer, and the thickness of the n-Si material layer is 120-140 mu m.
6. The method of claim 1, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: adopts a light injection mode to select ITO/SiO for the cavityxThe interface state density of the (In)/n-Si heterojunction photovoltaic device is measured, and the interface state density is deduced from the obtained C-V curve.
7. The method of claim 1, comprising the steps of:
a. introducing light injection into the SQIS heterojunction battery to be detected;
b. moving the SQIS heterojunction battery in the step a to an Agilent capacitance-voltage (C-V) test system, setting the frequency to be 1MHz and keeping the frequency unchanged, and ensuring that differential capacitance has response;
c. measuring the SQIS heterojunction device in the step b under illumination and darkness to obtain a corresponding C-V curve, wherein in the experiment, a direct current bias voltage applied to a front electrode of the device is swept from a depletion region to an accumulation region to change the width of the depletion region, and the scanning step length is 0.05V/s; when negative bias is applied, the silicon surface forms an inversion layer, and the shielding effect of the holes makes the total capacitance change very small until the bias is appliedAbove 0V, the total capacitance changes rapidly, and at the moment, the width of the depletion region changes rapidly under the influence of an external bias voltage; since the overflow voltage is related to the thickness of the interface region, the overflow voltage V isTMore than 2.0V, the external bias voltage is set to-1.0V, and the other signal is a high-frequency detection signal for detecting capacitance values under different bias voltages;
d. C-V curves respectively obtained under the dark and light conditions in the step C are analyzed and processed, and when the C-V curves are processed, the C-V curves in the dark are translated to the left by a theoretical photoproduction voltage value to obtain C-V curves under ideal light;
e. and d, obtaining the information of the interface state density from the C-V curve under the ideal illumination obtained in the step d, and obtaining the interface state density through an interface state density calculation formula.
8. The method of claim 7, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: in step c, the width of the depletion region in the light condition is influenced by the combined action of the photogenerated voltage and the DC bias voltage, while the depletion region in the dark condition is only influenced by the applied bias voltage.
9. The method of claim 7, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: in the step a, a tungsten filament bulb with power not lower than 20W is placed right above the SQIS heterojunction battery to be tested, and light injection is introduced.
10. The method of claim 7, wherein the step of measuring the interface state of the silicon-based photovoltaic device comprises: in the step a, the device area of the SQIS heterojunction battery to be tested is not more than 1cm2And the thickness is not more than 150 mu m.
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