JP2017028906A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion device in which a current, outputted from a photoelectric conversion layer, can be outputted easily to the outside even when a plurality of photoelectric conversion layers having different bandgaps are provided.SOLUTION: A photoelectric conversion device includes a plurality of photoelectric conversion layers 1, 3 connected in series and having different bandgaps, and a bypass circuit 9 detouring the photoelectric conversion layer 3 having a large bandgap out of the plurality of photoelectric conversion layers 1, 3. The bypass circuit 9 includes a sensor 17, and a switch 19 that is opened when the measured value of the sensor 17 goes above a specified value, and short-circuited when the measured value goes below the specified value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoelectric conversion device such as a solar battery.

  A solar cell (hereinafter referred to as a photoelectric conversion device) has an advantage that the amount of carbon dioxide emission per power generation amount is small and fuel is not required for power generation. Therefore, research on various types of photoelectric conversion devices has been actively promoted. At present, single-junction type photoelectric conversion devices having a pair of pn junctions using single crystal silicon or polycrystalline silicon are mainstream among photoelectric conversion devices in practical use.

  Since conventional single-junction type photoelectric conversion devices use silicon as a material for forming a photoelectric conversion layer, practical photoelectric conversion efficiency is limited to about 15% at most.

  In recent years, there has been a movement to review thermal power generation and nuclear power generation based on lessons learned from measures against global warming and nuclear accidents. Along with this, power generation using natural energy has been promoted. Photoelectric conversion devices represented by solar cells With regard to the above, further improvement in photoelectric conversion efficiency is desired.

  In response to such a problem, the present applicant has previously proposed a photoelectric conversion device 100 as shown in FIG. 5 in which a quantum dot integrated film 105 having a larger band gap than silicon is stacked on a silicon semiconductor substrate. (For example, see Patent Documents 1 and 2).

  FIG. 5A is a schematic cross-sectional view showing an example of a conventional photoelectric conversion device 100, and FIG. 5B is a circuit diagram in the configuration of FIG. 101 is a first conductor layer, 103 is a silicon substrate, 105 is a photoelectric conversion layer (in this case, a quantum dot integrated film) having a larger band gap than the silicon substrate, and 107 is a second conductor layer. When the second conductor layer 107 is located on the light incident side, a transparent conductive film is used as the second conductor layer 107.

  6 is a conceptual diagram of current-voltage lines of the photoelectric conversion device shown in FIG. In FIG. 6, the solid line corresponds to the current-voltage curve of the silicon substrate, and the broken line corresponds to the current-voltage curve of the integrated film 105 of quantum dots having a larger band gap than the silicon substrate.

  The photoelectric conversion efficiency of the photoelectric conversion device 100 is roughly calculated by calculating the open-circuit voltage as Voc and the short-circuit current density (the value obtained by dividing the short-circuit current Isc by the light receiving area of the solar cell) as Jsc. Shown as a divided value. In addition, the wavelength range of light that can be absorbed is limited to a region whose upper limit is the band gap (about 1.1 eV in the case of a silicon substrate) of the material constituting the light absorption layer (sometimes referred to as a photoelectric conversion layer). For this reason, in order to improve the photoelectric conversion efficiency of the photoelectric conversion device 100, it is necessary to form a light absorption layer that has a higher band gap and can naturally increase the open circuit voltage (Voc).

JP 2013-105952 A JP 2013-229378 A

However, since the quantum dot integrated film 105 has a larger band gap than the silicon substrate 103, the amount of power generation (maximum output (Pmax)) with respect to the amount of light to be irradiated is large. Below, the short circuit current (Isc) is greatly reduced, and instead of performing the function as the photoelectric conversion layer 105, it may become almost an insulator. For this reason, in the photoelectric conversion device 100 in which the quantum dot integrated film 105 is stacked on the silicon substrate 103, it may be difficult to output the current output on the silicon substrate 100 side to the outside.

  Therefore, an object of the present invention is to provide a photoelectric conversion device that easily outputs a current output from a photoelectric conversion layer to the outside even when a plurality of photoelectric conversion layers having different band gaps are provided.

  The photoelectric conversion device of the present invention includes a plurality of photoelectric conversion layers having different band gaps connected in series, and a bypass circuit that bypasses a photoelectric conversion layer having a large band gap among the plurality of photoelectric conversion layers. The bypass circuit includes a sensor unit and a switch unit that is in an open state when a measured value measured by the sensor unit is equal to or greater than a specified value, and that is in a short circuit state when the measured value falls below the specified value. It is.

  According to the present invention, even when a plurality of photoelectric conversion layers having different band gaps are provided, the current output from the photoelectric conversion layer can be easily output to the outside.

It is a circuit diagram which shows a structure when a light quantity sensor is applied to a sensor part as one embodiment of the photoelectric conversion device of the present invention, and (a) shows the same when the bypass circuit is in an open state. This is a case where the bypass circuit is in a short state. It is a circuit diagram which shows a structure when a current sensor is applied to a sensor part as one embodiment of the photoelectric conversion device of the present invention, and (a) shows a case where the bypass circuit is in an open state, and (b) shows the same. This is a case where the bypass circuit is in a short state. It is a circuit diagram which shows a structure when a temperature sensor is applied to a sensor part as one embodiment of the photoelectric conversion device of the present invention, and (a) shows the same when the bypass circuit is in an open state. This is a case where the bypass circuit is in a short state. It is a conceptual diagram of the current-voltage line of the photoelectric conversion device of the present embodiment, where (a) shows a large output of the sensor unit and the bypass circuit is in an open state, and (b) shows a small output of the sensor unit. This is a case where the bypass circuit is in a short-circuit state. (A) is a cross-sectional schematic diagram which shows the conventional photoelectric conversion apparatus, (b) is a circuit diagram in the structure of (a). It is a conceptual diagram of the general electric current-voltage line of a photoelectric conversion apparatus.

  Hereinafter, the photoelectric conversion devices shown in FIGS. 1 to 3 differ only in the sensor unit. Therefore, the circuit configuration other than the sensor unit will be described with reference to FIG. 1 in which a light amount sensor is applied as the sensor unit.

  FIG. 1 is a circuit diagram showing a configuration when a light amount sensor is applied to a sensor unit as an embodiment of a photoelectric conversion device of the present invention. FIG. 1A shows a case where a bypass circuit is in an open state, FIG. ) Is when the bypass circuit is in a short-circuit state.

The photoelectric conversion device illustrated in FIG. 1 includes a plurality of photoelectric conversion layers 1 and 3 having different band gaps, and the photoelectric conversion layers 1 and 3 are connected in series. An electrode layer 5 and a transparent conductive film 7 are provided on the lower side of the photoelectric conversion layer 1 and the upper side of the photoelectric conversion layer 3, respectively. In this case, the transparent conductive film 7 side is the sunlight incident surface side. In FIGS. 1A and 1B, for convenience, the band gap of the photoelectric conversion layer 3 is larger than the band gap of the photoelectric conversion layer 1. Here, the band gap is different when the plurality of photoelectric conversion layers 1 and 3 are compared with each other when the difference in the band gap is 0.2 eV or more between the two layers.

  In this photoelectric conversion device, a bypass circuit 9 is provided on the photoelectric conversion layer 3 side having a large band gap. As shown in FIGS. 1A and 1B, the bypass circuit 9 is connected by a wiring 11 that bypasses the photoelectric conversion layer 3 so that a potential difference between both main surfaces can be measured. That is, one end 13 of the wiring 11 constituting the bypass circuit 9 is connected between the photoelectric conversion layer 1 and the photoelectric conversion layer 3, and the other end 15 is connected between the photoelectric conversion layer 3 and the transparent electrode layer 7. It is the composition which becomes.

  The bypass circuit 9 includes a sensor unit 17 and a switch unit 19. Here, a light amount sensor 17 a is applied to the sensor unit 17. The light quantity sensor 17a is placed on the light receiving surface side of the photoelectric conversion layer 3 and has a function of measuring the amount of sunlight radiated and converting the light energy into electric energy to obtain an electromotive force. . As the light quantity sensor 17a, for example, a compound semiconductor such as InGaAs or GaAs is preferably used.

  On the other hand, the switch unit 19 includes a cut portion 11a provided in the wiring 11 constituting the bypass circuit 9, and a contact member 21 for connecting or disconnecting the cut portion 11a. And a coil 23 provided so as to be adjacent to 21. In this case, the coil 23 generates a magnetic field by the current from the light amount sensor 17a, and performs electrical switching by bringing the contact member 21 into contact with or being separated from the cutting portion 11a by this magnetic field. . That is, the switch unit 19 turns on / off the connection state of the wiring 11 according to the amount of sunlight irradiated to the photoelectric conversion layer 3 in the bypass circuit 9 provided to bypass the photoelectric conversion layer 3. It has the function of a relay circuit.

As shown in FIG. 1 (a) (b), for example, high, low, to set the dose of two sunlight irradiation amount of higher and first dose S _1, the first dose S ₁ second and dose S ₂ a lower dose than. Switching unit 19 photoelectric conversion device including a, for example, when it reaches the first dose S ₁ is a high dose towards increased electromotive force from the light quantity sensor 17a, the measurement value measured in the sensor portion 17 It becomes the specified value or more set in the sensor unit 17. Based on this, a large magnetic field is generated in the coil 23 of the switch unit 19 to bring the contact member 21 away from the cut portion 11a, and the bypass circuit 9 is opened. When the amount of irradiation with sunlight is large, the photoelectric conversion layer 3 with a large band gap exhibits a high power generation amount. Therefore, as a photoelectric conversion device, the photoelectric conversion layer 1 and the photoelectric conversion layer 3 are separated from both layers. It can generate electricity.

Conversely, a light irradiation amount is reduced from the sun to the photoelectric conversion device receives comprising bypass circuit 9, when the change in the so-called second state of dose S _2, as shown in FIG. 1 (b), the amount of light Since the electromotive force from the sensor 17a is reduced, the measured value measured by the sensor unit 17 is lower than the specified value set for the sensor unit 17. Based on this, the strength of the magnetic field generated in the coil 23 is reduced, and the contact member 21 constituting the switch unit 19 is brought into contact with the cut portion 11a of the wiring 11 so as to be connected. Thus, the bypass circuit 9 is changed to a short state (shorted state). Thereby, a current (or carrier (electron, hole)) flowing between the photoelectric conversion layer 1 and the transparent conductive film 7 mainly flows through the wiring 11 of the bypass circuit 9. When the irradiation amount of light from the sun is small, the photoelectric conversion layer 3 having a large band gap has a small amount of power generation and is in a state close to a so-called insulator.
Can be used to generate power from the photoelectric conversion layer 1 without passing through the photoelectric conversion layer 3. In this case, when the above-described relay circuit is used for the switch unit 19, the bypass circuit 9 can be formed in a small size and at a low cost.

  FIG. 2 is a circuit diagram showing a configuration when a current sensor is applied to the sensor unit as an embodiment of the photoelectric conversion device of the present invention. FIG. 2A shows a case where the bypass circuit is in an open state, FIG. ) Is when the bypass circuit is in a short-circuit state.

  The photoelectric conversion device shown in FIG. 2 turns on and off the bypass circuit 9 by using the change in the amount of current generated by the power generation from the photoelectric conversion layers 1 and 3 caused by the change in the amount of sunlight irradiated. In this case, as the sensor unit 17, a coil-type current sensor 17b can be cited as an example.

  When the irradiation amount of light from the sun irradiated to the photoelectric conversion device increases, the amount of current flowing between the photoelectric conversion layer 3 and the transparent conductive film 7 increases. At this time, in the photoelectric conversion device, the electromotive force from the current sensor 17b also increases. As a result, as shown in FIG. 2A, the contact member 21 is separated from the cut portion 11a by the magnetic field generated in the coil 23 in the switch unit 19, and the bypass circuit 9 is opened.

  On the other hand, when the amount of irradiation of light from the sun is small, the amount of current flowing between the photoelectric conversion layer 3 and the transparent conductive film 7 is reduced, so that the electromotive force from the current sensor 17b is also reduced. In this case, as shown in FIG. 2B, since the strength of the magnetic field generated in the coil 23 in the switch unit 19 is small, the contact member 21 is in contact so as to connect the cut portion 11a of the wiring 11. The bypass circuit 9 enters a short state (short-circuited state).

  FIG. 3 is a circuit diagram showing a configuration when a temperature sensor is applied to the sensor unit as one embodiment of the photoelectric conversion device of the present invention. FIG. 3A shows a case where the bypass circuit is in an open state, FIG. ) Is when the bypass circuit is in a short-circuit state. In this photoelectric conversion device, the sensor unit 17 includes a temperature sensor 17 c that detects the temperature near the photoelectric conversion layer 3.

  For example, when the photoelectric conversion layers 1 and 3 are stacked on a glass plate and covered and fixed with a member having low thermal conductivity such as an organic resin, the temperature of the photoelectric conversion device is higher than the outside air temperature. Self-heating by the power generation of the conversion layers 1 and 3 becomes dominant. For this reason, the temperature of the photoelectric conversion layers 1 and 3 can also be an element that causes the sensor unit 17 to function. That is, the photoelectric conversion device shown in FIG. 3 turns on and off the bypass circuit 9 by using a temperature change of the photoelectric conversion layer 3 itself generated by a change in the amount of sunlight irradiated.

  When the amount of irradiation with light from the sun is large, the temperature of the photoelectric conversion layer 3 increases depending on the high power generation amount. At this time, a large magnetic field is generated in the coil 23 of the switch unit 19 according to the electromotive force from the temperature sensor 17c. Thus, the contact member 21 is separated from the cut portion 11a, and the bypass circuit 9 is opened.

  On the contrary, when the amount of sunlight irradiation is small and the power generation amount of the photoelectric conversion layer 3 is low, the electromotive force from the temperature sensor 17c is also small, so that the contact member 21 in the switch unit 19 cuts the wiring 11 The locations 11a are connected, and the bypass circuit 9 is short-circuited (short-circuited).

In addition, about the switch part 19 shown in FIGS. 1-3, the point for amplifying the electromotive force obtained by the sensor part 17 between the sensor part 17 and the coil 23 from the point of improving the operation function of ON / OFF. An amplifier circuit may be provided, and the sensor unit 17 may control the switch unit 19. Furthermore, a control unit for controlling the switch unit 19 based on the measurement value of the sensor unit 17 may be provided separately.

  FIG. 4 is a conceptual diagram of a current-voltage line of the photoelectric conversion device of the present embodiment. FIG. 4A shows a case where the output of the sensor unit is large and the bypass circuit is in an open state, and FIG. This is a case where the output of the bypass circuit is small and the bypass circuit is in a short state.

  Based on FIGS. 4A and 4B, the currents of the two photoelectric conversion devices shown in FIGS. 1A and 1B, 2A and 2B, and 3A and 3B, respectively. When the voltage characteristics are compared, in the case of a photoelectric conversion device in which the photoelectric conversion layer 1 and the photoelectric conversion layer 3 having a larger band gap are combined, the photoelectric conversion layer 1 has a small band gap. Even if the irradiation amount decreases, the change in the short-circuit current (Isc) is small. On the other hand, in the photoelectric conversion layer 3 having a larger band gap, the short-circuit current (Isc) is greatly reduced when the amount of irradiation with light from the sun is reduced.

  That is, since the photoelectric conversion layer 3 has a larger band gap than the photoelectric conversion layer 1, the amount of power generation with respect to the amount of light emitted from the sun is large, so that the amount of light irradiated from the sun is low. Then, it becomes difficult to perform the function as the photoelectric conversion layer 3, and the insulation is increased. For this reason, in the photoelectric conversion device in which the photoelectric conversion layer 3 having a larger band gap than that of the photoelectric conversion layer 1 is connected in series, it is difficult to output the current output from the photoelectric conversion layer 1 to the outside.

  On the other hand, in the photoelectric conversion device shown in FIGS. 1 to 3, the photoelectric conversion layer 3 has a large band gap even under conditions where the photoelectric conversion layer 3 becomes an insulator due to a decrease in the amount of light irradiated from the sun. Current (or carriers (electrons e, holes h)) flows in the bypass circuit 9 provided in 3, so that the carriers (electrons e, holes h) generated in the photoelectric conversion layer 1 can be easily discharged to the outside. Can be moved.

  In the photoelectric conversion device of this embodiment, it is desirable that the bypass circuit 9 is provided on the photoelectric conversion layer side that directly receives sunlight. For example, as shown in FIGS. 1A and 1B, when the bypass circuit 9 is provided on the photoelectric conversion layer 3 side that directly receives sunlight, the photoelectric conversion device including the photoelectric conversion layer 3 includes: It is easy to synchronize the change in electromotive force by the light amount sensor 17a with the change in the amount of power generation, and thus a photoelectric conversion device that can respond sensitively to the change in the amount of sunlight irradiated can be obtained.

  In this photoelectric conversion device, it is desirable that the sensor unit 17 includes a temperature compensation circuit. For example, when the light quantity sensor 17a is formed of a material whose sensing property has temperature dependence, the sensitivity of the light quantity sensor 17a changes due to a change in environmental temperature. For this reason, the timing when the bypass circuit 9 is in an open state or a short state is influenced not only by the amount of sunlight irradiation but also by the environmental temperature. In such a case, if the temperature compensation circuit is provided in the light quantity sensor 17a, the sensitivity of the light quantity sensor 17a can be kept within a certain range even if the environmental temperature changes. Accordingly, a highly efficient photoelectric conversion device can be obtained even in an environment where the temperature of the outside air changes greatly.

  In the photoelectric conversion device of this embodiment, it is desirable that one of the photoelectric conversion layers 3 is a quantum dot integrated film. If the photoelectric conversion layer 3 is a quantum dot integrated film, the band gap of the photoelectric conversion layer 3 can be easily changed by changing the particle size and components of the quantum dots, so that the photoelectric conversion layer 3 can cover a wide wavelength region. A conversion device can be obtained.

  In this case, the main component of the photoelectric conversion layers 1 and 3 is preferably one selected from the group consisting of Si, GaAs, PbSe, CdSe, CuInGeSe, CuInGeS, CuZnGeSe, and CuZnGeS.

  When Si is used as the main component of the photoelectric conversion layers 1 and 3, for example, the photoelectric conversion layer 1 is a silicon substrate (band gap (about 1.1 eV)), and Si quantum dots are integrated in one photoelectric conversion layer 3. The film is arranged. In this case, since the band gap on the photoelectric conversion layer 3 side can be 1.5 eV or more and, depending on the particle size, 1.7 eV or more, a higher open circuit voltage (Voc) can be obtained, and the maximum output (Pmax) of power generation can be obtained. It can be further increased.

  In addition, if the photoelectric conversion layers 1 and 3 are both formed of silicon, there is almost no difference in the lattice constants of the materials, so that lattice mismatch between the photoelectric conversion layers 1 and 3 can be reduced. The mobility of carriers near the boundary between the photoelectric conversion layers 1 and 3 can be increased.

  The present invention has been described based on the photoelectric conversion device in which two layers of the photoelectric conversion layers 1 and 3 are stacked. However, the present invention is not limited to this, and a configuration in which three or more photoelectric conversion layers 1 and 3 are stacked. It can also be applied to.

  Next, the photoelectric conversion devices shown in FIGS. 1, 2, and 3 were manufactured and evaluated. Here, in addition to a silicon substrate having a band gap of 1.1 eV, aluminum is used for the electrode layer 5, indium tin oxide (ITO) is used for the transparent conductive film 7, and silicon photoelectric dots (bands) are used as the photoelectric conversion layer 3. A gap of 1.7 eV) was applied respectively. A light intensity sensor made of InGaAs was used as the light intensity sensor 17a constituting the bypass circuit 9. A coil produced by winding a copper wire was used as the current sensor. A platinum resistance thermometer was used as the temperature sensor 17c. Moreover, the photoelectric conversion apparatus which does not have a bypass circuit as shown in FIG. 5 was produced as a comparative example, and the same evaluation was performed.

  The power generation performance was evaluated for the obtained photoelectric conversion device and the photoelectric conversion device not having the bypass circuit 9 as a comparative example. As an evaluation method, power was generated during the daytime around noon and a time zone close to morning and evening, and the short-circuit current at that time was measured and compared.

  The photoelectric conversion device having the light quantity sensor 17a as the sensor unit 17 and including the bypass circuit 9 has a short circuit current (Isc) measured five times in the morning and evening compared with the photoelectric conversion device not having the bypass circuit 9. It was so expensive. Further, when the current sensor 17b or the temperature sensor 17c is provided as the sensor unit 17 instead of the light quantity sensor 17a, the same effect is obtained.

1, 3... Photoelectric conversion layer 5 ... Electrode layer 7 ... Transparent conductive film 9 ························································ (Wiring 11) One end 15... (Of the wiring 11) the other end 17... Sensor part 17 a... Light quantity sensor 17 b. Current sensor 17c Temperature sensor 19 Switch unit 21 Contact member 23 ········coil

Claims (6)

  A plurality of photoelectric conversion layers having different band gaps connected in series, and a bypass circuit that bypasses a photoelectric conversion layer having a large band gap among the plurality of photoelectric conversion layers, and the bypass circuit includes a sensor unit And a switch unit that is in an open state when a measured value measured by the sensor unit is equal to or greater than a specified value, and that is in a shorted state when the measured value falls below the specified value.   The photoelectric conversion device according to claim 1, wherein the sensor unit is any one of a light amount sensor, a current sensor, and a temperature sensor.   The photoelectric conversion device according to claim 1, wherein the bypass circuit is provided on a photoelectric conversion layer side that directly receives sunlight.   The photoelectric conversion device according to claim 1, wherein the sensor unit includes a temperature compensation circuit.   The photoelectric conversion device according to claim 1, wherein the switch unit is configured by a relay circuit.   6. The photoelectric conversion device according to claim 1, wherein one of the plurality of photoelectric conversion layers is a quantum dot integrated film.

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