JP2002033959A - Photoelectric conversion device and its drive method, and radiation imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fluctuations of sensor characteristics between the center and the end of a sensor panel, by carefully setting time for setting a refresh control circuit to Hi state and time for setting a TFT, that is a switching element to Hi state. SOLUTION: In a photoelectric conversion device having a photoelectric conversion element for converting light to an electrical signal and a switching element for controlling the read of an electrical signal that is converted by the photoelectric conversion element, the photoelectric conversion element is set to a constant potential, and at the same time, the switching element is turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device, a method of driving the same, and a radiation imaging system, and more particularly to a photoelectric conversion device and a method of driving the same, for example, a facsimile machine and a digital copier formed using a large area process. The present invention relates to an imaging system.

[0002]

2. Description of the Related Art Conventionally, a reduction optical system and a reading system using a CCD sensor have been used as a reading system of a facsimile, a digital copying machine, an X-ray imaging device, or the like. Hereinafter, "a
-Si ". With the development of the photoelectric conversion semiconductor material represented by (1), a so-called contact type sensor in which a photoelectric conversion element and a signal processing unit are formed on a large-sized substrate and read by an optical system of the same magnification as the medium to be read is remarkable.

In particular, since a-Si can be used not only as a photoelectric conversion material but also as a thin film field effect transistor, there is an advantage that a photoelectric conversion semiconductor layer and a semiconductor layer of a transistor can be formed simultaneously. are doing.

FIG. 1 is a circuit diagram of a photoelectric conversion device in which, for example, 3 × 3 pixels in which a photoelectric conversion semiconductor layer and a semiconductor layer of a transistor are simultaneously formed are arranged two-dimensionally. Figure 1
In S11 to S33, G denotes a lower electrode side and D denotes an upper electrode side. C11 to C33 are storage capacitors, which are indicated in the equivalent circuit in this way because the photoelectric conversion elements of S11 to S33 function as capacitors.

Further, T11 to T33 are transfer transistors. Vs is a read power supply and Vg is a refresh power supply, which are connected to the D electrodes of all the photoelectric conversion elements S11 to S33 via switches SWs and SWg, respectively. The switch SWs is directly connected to the refresh processing circuit RF via the inverter, and the switch SWg is controlled so that the switch SWg is turned on during the refresh period.

In this photoelectric conversion device, a total of nine pixels are divided into, for example, three blocks in a column direction, and outputs of three pixels per block are simultaneously transferred to a detection integrated circuit IC through signal lines SIG1 to SIG3. The output is sequentially converted and output by the detection integrated circuit IC (Vout). Each pixel is two-dimensionally arranged by arranging three pixels in one block in, for example, a row direction and arranging three blocks in a column direction in order.

Here, when the signal charge Q stored in the photoelectric conversion element S11 is transferred to SIG1 via the transistor T11 and is read by Amp via the switch M1, Cgs is connected to the gate of the transistor and the signal line. Assuming that the overlap capacitance is C _cross and the overlap capacitance between the Vg line and the signal line is CAmp, CAmp is Vo, which is the read capacitance of Amp.
ut may be expressed as Vout = Q / (ΣCgs + ΣC cross + CAmp). FIG. 1 shows the transistor T
11 and Cgs only between g2 and SIG1
_cross is shown, but in fact, other transistors T
Cgs also exist in 12 to T33, and control wirings g2 and g3
C _cross also exists between the signal line SIG1 and the signal lines SIG1 to SIG3.

FIG. 6 is a timing chart showing the operation of FIG. Next, the operation of the photoelectric conversion device of FIG. 1 will be described with reference to FIG. First, the shift register S
Control wirings g1 to g3, s1 to s2 by R1 and SR2
Is applied. Then, the transfer transistor T1
1 to T33 and switches M1 to M3 are turned on to conduct.

The G electrodes of all the photoelectric conversion elements S11 to S33 are at the GND potential (the input terminal of the integration detector Amp is GND).
D potential). At the same time, the refresh processing circuit RF outputs Hi, the switch SWg is turned on, and the D electrodes of all the photoelectric conversion elements S11 to S33 become positive potential by the refresh power supply Vg.

Thus, all the photoelectric conversion elements S11 to S3
No. 3 enters the refresh mode and is refreshed.
Next, when the refresh processing circuit RF outputs Lo and the switch SWs is turned on, all the photoelectric conversion elements S11
The D electrode in steps S33 to S33 is set to a higher positive potential by the reading power supply Vs.

Then, all the photoelectric conversion elements S11 to S33 enter the photoelectric conversion mode, and at the same time, the capacitors C11 to C33
Is initialized. In this state, Lo is applied to the control wires g1 to g3 and s1 to s2 by the shift registers SR1 and SR2. Then, the transfer transistors T11 to T33
Switches M1 to M3 are turned off, and all the photoelectric conversion elements S1
The G electrodes 1 to S33 are DC open, but the potential is held by the capacitors C11 to C33.

Thereafter, when light is emitted from a light source (not shown), the light is transmitted to each of the photoelectric conversion elements S11 to S33.
Incident on. The photocurrent flowing by this light is accumulated as electric charges in the respective capacitors C11 to C33, and is retained even after the end of X-ray incidence.

Next, a control pulse of Hi is applied to the control wiring g1 by the shift register SR1, and the control pulse is applied to the control wirings s1 to s3 of the shift register SR2 to switch M1 of the transfer transistors T11 to T33.
V1 to v3 are sequentially output through. Similarly,
Other optical signals are sequentially output under the control of the shift registers SR1 and SR2.

In this photoelectric conversion device, the D electrode of the photoelectric conversion element is commonly connected, and this common wiring is connected to the switch SWg.
And the switches SWs, the potential of the refresh power supply Vg and the potential of the read power supply Vs are controlled, so that all the photoelectric conversion elements can be simultaneously switched to the refresh mode and the photoelectric conversion mode. Therefore, an optical output can be obtained with one transistor per pixel without complicated control.

[0015]

However, the characteristic specifications of a large-area photoelectric conversion device are becoming stricter year by year. Particularly, in a two-dimensional photoelectric conversion device such as an X-ray imaging device which reads at the same magnification, There is a demand to reduce X-rays affecting the human body as much as possible and to obtain more accurate data uniformly and in a short time within a two-dimensional area. In order to reduce the variation of the signal output of the sensor as much as possible and to drive it in a short time, it is conceivable to devise the operation of the control wiring in the sensor refreshing method.

Here, in order to make the output of a plurality of signals within the two-dimensional area more uniform and to further improve the quality of the sensor panel, 5 × 5 pixels per 1 mm in length and width are assumed to be 2 pixels.
2,000 x 2000 pixels, two-dimensionally arranged 4
An X-ray detector of 0 cm × 40 cm is constructed and its operation is
Considering a case where a moving image is obtained by scanning 10 sheets per second, the time per sheet is 100 ms, the time per line is 50 microseconds, and the time required for the refresh mode is zero. , Signal readout IC
The time to perform the multiplexer in is 2 per signal.
5 ns.

The value of 25 ns per signal is a relatively high speed for current analog ICs, which is severe. Therefore, it is difficult to perform the refresh mode for an excessively long time.

Here, as shown in FIG. 6, when the actual refresh processing circuit RF is set to Hi, the capacitors C11 + C12 + C13 + C21 +... + C3 in FIG.
It has a capacity of 3 and a capacity of C _cross × 9 pixels. For example, in the case where an X-ray detector of 40 cm × 40 cm is formed by two-dimensionally arranging 5 × 5 pixels as 2000 × 2000 pixels per 1 mm in length and width, one capacitor C11 is used. Is about 4 pF
Thus, one C _cross has a negligible value for the capacitor C11.

Therefore, the total capacitance of the line connecting the refresh control circuit and the photoelectric conversion element is 4 pF × 2000 × 2000 = 16 μF.

Here, the resistance value of the line connecting the refresh control circuit and the photoelectric conversion element is 1 in the case of aluminum having a width of 10 μm and a thickness of 5000 Å.
Since 4 k ohms per line, if 2000 lines are arranged in parallel, 4 k ohms / 2000 = 2 ohms when considering all lines. Therefore, considering the time constant of the line connecting the refresh control circuit and the photoelectric conversion element, R × C = 16 μF × 2 ohm = 32 μsec. Therefore, when the time when the refresh control circuit RF is set to Hi is five times R × C, 32 μs × 5 = 160 μs.

Therefore, as the area of the sensor section of the X-ray detector increases and the number of elements increases, it is necessary to increase the time during which the refresh processing circuit RF is kept Hi.
In particular, the potential at the end of the line connecting the refresh control circuit and the photoelectric conversion element has a large resistance value and a large capacitance value, so that the pulse delay becomes large, so that the sensor is not sufficiently refreshed and a normal signal is output. No output can be obtained. That is, when the area of the sensor unit of the X-ray detector becomes large, it becomes difficult to obtain a normal signal uniformly in the sensor panel.

However, if all the 2,000 control lines are simultaneously turned on by the shift register SR1 and 2,000 switches M1 to M2000 are simultaneously turned on by the shift register SR2, a large current consumption occurs. Therefore, the control wirings g1 to g2000 and the switches M1 to M2
Signal lines s1 and s2 for turning on 2,000 pieces at the same time
It is necessary to minimize the time required to make 000 Hi.

Further, in FIG. 6, after the refresh processing circuit RF changes from Hi to Lo, the time until the signal applied to the control wiring g1 changes from Hi to Lo is determined by the time between the refresh control circuit and the photoelectric conversion element. It takes a certain amount of time for the potential of the connected line to stabilize.

Therefore, taking the above into consideration, 1 m
When a 5 × 5 pixel per m is two-dimensionally arranged as about 2000 × 2000 pixels to configure an X-ray detector of about 40 cm × 40 cm, or to configure an X-ray detector larger than that , The refresh processing circuit R
It is considered effective to advance the time when F is set to be higher than the time when the control wiring g1 is set to be Hi.

Therefore, according to the present invention, the time when the refresh control circuit is set to Hi and the TFT which is the switch element are set to Hi.
It is an object of the present invention to reduce the variation in sensor characteristics between the central part and the end part of the sensor panel by devising the time to be set.

[0026]

In order to solve the above-mentioned problems, the present invention provides a photoelectric conversion element for converting light into an electric signal, and a switch element for controlling reading of the electric signal converted by the photoelectric conversion element. In a photoelectric conversion device comprising:
A control unit for turning on the switch element is provided.

Further, the radiation imaging system of the present invention comprises the above-mentioned photoelectric conversion device, signal processing means for processing a signal from the photoelectric conversion device, recording means for recording a signal from the signal processing means, A display unit for displaying a signal from the signal processing unit; a transmission processing unit for transmitting a signal from the signal processing unit; and the photoelectric conversion device which converts radiation irradiated from a radiation source into light and converts the radiation to light. And a scintillator for causing the light to enter.

Furthermore, a method of driving a photoelectric conversion device according to the present invention includes a photoelectric conversion element for converting light into an electric signal, and a switch element for controlling reading of the electric signal converted by the photoelectric conversion element. In the conversion device, the switch element is turned on while the photoelectric conversion element is kept at a constant potential.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram of a radiation imaging apparatus according to Embodiment 1 of the present invention. FIG. 1 is a circuit diagram of a photoelectric conversion device in which, for example, 3 × 3 pixels in which a photoelectric conversion semiconductor layer and a semiconductor layer of a transistor are simultaneously formed are two-dimensionally arranged. In FIG. 1, S11 to S33 are photoelectric conversion elements, and the lower electrode side is denoted by G, and the upper electrode side is denoted by D. C11 to C33 are storage capacitors;
This is shown in the equivalent circuit because the photoelectric conversion elements 11 to S33 function as capacitors.

T11 to T33 are transfer transistors which are switch elements. Vs is a read power supply, Vg is a refresh power supply, and all the photoelectric conversion elements S11 to S11 are connected via switches SWs and SWg, respectively.
It is connected to the D electrode of S33. The switch SWs is directly connected to the refresh processing circuit RF via the inverter, and the switch SWg is controlled so that the switch SWg is turned on during the refresh period.

This photoelectric conversion device divides a total of nine pixels into, for example, three blocks in the column direction, and simultaneously transfers outputs of three pixels per block to the detection integrated circuit IC through the signal lines SIG1 to SIG3. The output is sequentially converted and output by the detection integrated circuit IC (Vout). Each pixel is two-dimensionally arranged by arranging three pixels in one block in, for example, a row direction and arranging three blocks in a column direction in order.

Here, when the signal charge Q stored in the photoelectric conversion element S11 is transferred to SIG1 via the transistor T11 and further read by Amp via the switch M1, Cgs is connected to the gate of the transistor and the signal line. Assuming that the overlap capacitance is C _cross and the overlap capacitance between the Vg line and the signal line is CAmp, CAmp is Vo, which is the read capacitance of Amp.
ut may be expressed as Vout = Q / (ΣCgs + ΣC cross + CAmp). FIG. 1 shows the transistor T
11 and Cgs only between g2 and SIG1
_cross is shown, but in fact, other transistors T
Cgs also exist in 12 to T33, and control wirings g2 and g3
C _cross also exists between the signal line SIG1 and the signal lines SIG1 to SIG3.

FIG. 2A is a schematic diagram of one pixel provided in the photoelectric conversion device of FIG. FIG. 2B is a cross-sectional view taken along a line AB in FIG. FIG. 2 (a), FIG.
As shown in (b), this pixel is provided with a sensor 8 (photoelectric conversion element) and a transistor 9 (TFT) on a glass substrate 7. The sensor 8 and the transistor 9 are simultaneously formed by an amorphous silicon thin film process.

The sensor 8 is of the MIS type. The sensor 8 and the transistor 9 sequentially form a lower metal layer 10, an insulating layer 11, a semiconductor layer 12, an n ⁺ layer 13, an upper metal layer 14, and a protective layer (not shown) such as an amorphous silicon nitride film or polyimide on a glass substrate 7. The film is formed by patterning.

FIG. 3 is an equivalent circuit of the photoelectric conversion element of FIG. As shown in FIG. 3, the photoelectric conversion element performs a reading operation by generating charges in accordance with the amount of light incident on the sensor 8 and transferring the charges to a reading device (not shown) by the transistor 9.

FIG. 4 is a timing chart showing the operation of FIG. 1 in the present embodiment. The operation shown in FIG. 4 is executed by a control unit (not shown). As shown in FIG. 4, in the present embodiment, first, it outputs the refresh processing circuit RF is Hi at time T ₁ the switch SWg
There was on, in a state D electrodes of all the photoelectric conversion elements S11~S33 is a positive potential by the refresh power supply Vg, the control lines by the shift registers SR1 and SR2 at time T ₂ g 1 -g 3, is Hi in s1~s3 applied Is done.

Then, the transfer transistors T11 to T3
3 and switches M1 to M3 are turned on to conduct. The G electrodes of all the photoelectric conversion elements S11 to S33 have the GND potential (because the input terminals of the integration detector Amp are designed to have the GND potential). At the same time, the capacitors C11 to C33 are initialized.

Thus, all the photoelectric conversion elements S11 to S3
No. 3 enters the refresh mode and is refreshed.
Then, the refresh processing circuit RF at time T ₃ is by switch SWs outputs Lo is on, D electrodes of all the photoelectric conversion elements S11~S33 becomes higher positive potential by the reading power supply Vs.

[0040] Then, all the photoelectric conversion elements S11~S33 becomes the photoelectric conversion mode, the control lines by the shift registers SR1 and SR2 at time T ₄ in this state g1~g
3. Lo is applied to s1 to s2. Then, the switches M1 to M3 of the transfer transistors T11 to T33 are turned off.
The G electrodes of all the photoelectric conversion elements S11 to S33 are DC open, but the potential is held by the capacitors C11 to C33.

Thereafter, when light is emitted from a light source (not shown), the light is transmitted to each of the photoelectric conversion elements S11 to S33.
Incident on. The photocurrent flowing by this light is accumulated as electric charges in the respective capacitors C11 to C33, and is retained even after the end of X-ray incidence.

Next, a control pulse of Hi is applied to the control line g1 by the shift register SR1, and the control pulse is applied to the control lines s1 to s3 of the shift register SR2 to switch M1 of the transfer transistors T11 to T33.
V1 to v3 are sequentially output through. Similarly,
Other optical signals are sequentially output under the control of the shift registers SR1 and SR2.

In this photoelectric conversion device, the D electrode of the photoelectric conversion element is connected in common, and this common wiring is connected to the switch SWg.
And the switches SWs, the potential of the refresh power supply Vg and the potential of the read power supply Vs are controlled, so that all the photoelectric conversion elements can be simultaneously switched to the refresh mode and the photoelectric conversion mode. Therefore, an optical output can be obtained with one transistor per pixel without complicated control.

Here, at least the time T ₁ at which the refresh processing circuit RF is set to Hi may be temporally earlier than the time T _{2 at} which the control pulse of the control lines g ₁ to g 3 is set to Hi. Further, the interval between the time T ₁ and time T _2, by the refresh processing circuit RF to Hi, when noise generated by the switch SWg is on is, you Hi control pulse of the control wire g1~g3 Signal line SI
Since it is preferable not to superimpose on the signals flowing through G1 to SIG3, it is desirable to set the interval to about 10 μs. By the way, if the interval is not sufficient, the influence of the bias variation between the center and the end of the sensor panel is different, so that the variation in the sensor characteristics may appear to be relatively large.

Further, as an essential condition for refreshing,
Set the refresh processing circuit RF to Hi and control wiring g
Because it mentioned be a Hi control pulse 1～G3, time T ₃ to the processing circuit RF to Lo, the time T ₄ to the time T _2, the control line g1~g3 to all lines simultaneously Lo
It is necessary to be between In the present embodiment, driving is performed such that T ₂ −T ₁ = T ₃ −T ₂ = T ₄ −T ₃ .

Thus, even when a large X-ray detector is formed, the potential of the line connecting the refresh control circuit and the photoelectric conversion element can be sufficiently set to the Hi state, and the refresh of the sensor can be performed. It is performed uniformly and normally in the sensor panel, and as a result, a normal signal output can be uniformly obtained in the sensor panel.

Further, in this embodiment, the control wirings g1 to g
3. The pulse applied to s1 to s3 is set to a necessary minimum without lengthening the time for which Hi is applied, and only the time for which the refresh processing circuit RF is set to Hi is increased. Therefore, the power can be reduced and the power source can be reduced in size and cost can be reduced.

(Embodiment 2) FIG. 5 is a block diagram showing the configuration of an X-ray imaging system according to Embodiment 2 of the present invention.
In FIG. 5, 101 is a patient, 102 is an X-ray source, 103
Is a phosphor (scintillator), 104 is the photoelectric conversion device described in the first embodiment, 105 is a shooting switch, 106 is a display, 107 is a processing circuit, and 108 is a drive circuit.

Here, an X-ray detector of 40 cm × 40 cm is obtained by arranging, for example, 5 × 5 pixels per 1 mm in length and width as 2000 × 2000 pixels two-dimensionally. If this is combined with an X-ray generator instead of an X-ray film to constitute an X-ray radiograph, it can be used for chest X-ray examination and breast cancer examination. Then, unlike a film, the output is instantaneously output to a cathode ray tube (CRT).
(Tube: CRT) or the like, and the output can be converted to digital, processed by a computer for image processing, and converted to an output suitable for the purpose.

Next, the operation of FIG. 5 will be described.
First, the photographing switch 105 is turned on with the patient 101 standing in front of the phosphor 103. Then, a drive signal is output from the drive circuit 108 to drive the X-ray source 102. The X-ray source 102, based on the drive signal,
Irradiate X-rays. Thus, the X-ray information of the patient 101 is sent to the photoelectric conversion device 104 side.

This X-ray is converted by the phosphor 103 into, for example, visible light. The visible light enters the photoelectric conversion device 104 and is output to the processing circuit 107 as image information.
The processing circuit 107 performs predetermined image processing on the output image information and causes the display 106 to display the processed image information.

The information after the image processing by the processing circuit 107 can be stored in a magneto-optical disk or the like, and a past image can be retrieved instantaneously. Also, the sensitivity is better than that of a film, and a clear image can be obtained with weak X-rays having little effect on the human body.

In this embodiment, the photoelectric conversion device is
Although the case of applying to an X-ray diagnostic system has been described,
The present invention can also be applied to a radiation imaging system such as a non-destructive inspection device using radiation other than X-rays such as α-rays, β-rays, and γ-rays. Further, in the X-ray imaging system of the present embodiment, a case has been described in which X-rays are converted to light using a phosphor and the converted light is further converted to an electric signal, but the X-rays are directly converted to electric signals. A material to be converted may be used.

[0054]

As described above, according to the present invention,
Since the switch element is turned on with the photoelectric conversion element kept at a constant potential, variation in sensor characteristics between the center and the end of the sensor panel can be reduced. Accordingly, the sensor characteristics of a plurality of signal outputs in a two-dimensional area having a relatively large area can be made uniform without increasing power consumption, so that the quality of the sensor panel can be improved. is there.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention and a conventional radiation imaging apparatus.

FIG. 2 is a schematic diagram of one pixel provided in the photoelectric conversion device of FIG. 1;

FIG. 3 is an equivalent circuit of the photoelectric conversion element in FIG.

FIG. 4 is a timing chart showing the operation of FIG. 1 in the present embodiment.

FIG. 5 is a block diagram illustrating a configuration of an X-ray imaging system according to a second embodiment of the present invention.

FIG. 6 is a timing chart showing a conventional operation.

[Explanation of symbols]

 S11 to S33 Sensor T11 to T33 TFT C11 to C33 Capacitor SR1, SR2 Shift register IC Detection integrated circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G06T 1/00 430 G06T 1/00 430D 5F049 H01L 27/146 H04N 1/028 A 5F088 27/14 H01L 27 / 14 A 31/09 D 31/10 31/00 A H04N 1/028 31/10 GF term (Reference) 2G088 EE01 EE27 FF02 FF14 GG19 GG21 JJ05 JJ31 KK05 KK32 KK35 LL11 LL12 LL15 LL16 LL17 LL18 4M118 AA05 AA06 AB CB11 DD12 FB09 FB13 FB16 GA10 5B047 AA17 AB02 BA02 BB04 BC01 CA06 CB17 5C024 AX12 CX27 CX35 CY02 CY16 CY47 GX09 HX01 HX35 HX40 JX41 5C051 AA01 BA02 DA06 DB01 DB04 DB08 DC03 MA02 NA03 EA02 BA20 BB02 BB07 EA07 EA08 GA02 JA17 KA01 LA07

Claims (8)

[Claims] 1. A photoelectric conversion device comprising: a photoelectric conversion element for converting light into an electric signal; and a switch element for controlling reading of the electric signal converted by the photoelectric conversion element, wherein the photoelectric conversion element has a constant potential. A photoelectric conversion device comprising control means for turning on the switch element in the state described above. 2. The photoelectric conversion device according to claim 1, wherein said control means turns on said switch element when not affected by noise generated by setting said photoelectric conversion element at a constant potential. . 3. The control device according to claim 1, wherein the control unit releases the state in which the photoelectric conversion element is kept at a constant potential after turning on the switch element and before turning off the switch element. 3. The photoelectric conversion device according to claim 1. 4. The control unit sets a period from when the photoelectric conversion element is set at a constant potential to when the switch element is turned on, and when the switch element is turned on and the photoelectric conversion element is set at a constant potential. 4. The method according to claim 1, wherein a period from when the photoelectric conversion element is kept at a constant potential to a time when the switch element is turned off is equal to a period until the switch element is released. 5. Item 6. The photoelectric conversion device according to Item 1. 5. A first electrode layer, an insulating layer, a photoelectric conversion semiconductor layer, and a semiconductor layer for preventing injection of carriers of a first conductivity type on a substrate on which the photoelectric conversion element and the switch element are formed. And a photoelectric conversion element in which a second electrode layer is laminated, and a carrier of a first conductivity type generated by signal light incident on the photoelectric conversion semiconductor layer is allowed to remain in the photoelectric conversion semiconductor layer, and the first conductivity type A photoelectric conversion unit that applies an electric field to the photoelectric conversion element in a direction that guides the second conductivity type carrier to the second electrode layer; and applying an electric field to the photoelectric conversion element to convert the first conductivity type carrier. Refresh means for applying an electric field to the photoelectric conversion element in a direction leading from the photoelectric conversion semiconductor layer to the second electrode layer; and the first means stored in the photoelectric conversion semiconductor layer during a photoelectric conversion operation by the photoelectric conversion means. Guidance The signal detection part for detecting an electric type carrier or the said 2nd conductive type | mold carrier led to the said 2nd electrode layer is provided, The Claim 1 characterized by the above-mentioned. Photoelectric conversion device. 6. A photoelectric conversion device according to claim 1, a signal processing unit for processing a signal from the photoelectric conversion device, and a signal processing unit for recording a signal from the signal processing unit. Recording means, display means for displaying a signal from the signal processing means, transmission processing means for transmitting a signal from the signal processing means, and converting radiation emitted from a radiation source into light A radiation imaging system comprising: a scintillator for causing the photoelectric conversion device to enter the photoelectric conversion device. 7. The radiation imaging system according to claim 6, wherein the scintillator is a phosphor. 8. A photoelectric conversion device comprising: a photoelectric conversion element for converting light into an electric signal; and a switch element for controlling reading of the electric signal converted by the photoelectric conversion element, wherein the photoelectric conversion element has a constant potential. The method for driving a photoelectric conversion device, wherein the switch element is turned on in the state described above.