JP2755616B2 - Photovoltaic device - Google Patents

Description

The present invention relates to a photovoltaic device that generates an electromotive force by receiving light irradiation.

(B) Conventional technology The light-receiving-surface-side electrode of a photovoltaic device that generates an electromotive force when irradiated with light may be translucent so as to induce light irradiation on a semiconductor photoactive layer that performs photoelectric conversion. preferable.
_{Conventionally, In 2 O 3, SnO 3} , translucent conductive oxide represented by ITO or the like is an oxide of order Teisu the translucent light-receiving surface side electrode is indium (In), tin (Sn) (hereinafter TCO). The electrode made of this TCO has a sheet resistance of about 30 to 50 Ω / □, which is more than three orders of magnitude higher than a metal material such as aluminum having the same film thickness. ) Occurs,
This may cause a reduction in current collection efficiency.

Therefore, the applicant of the present application has proposed a high-resistance electrode on the light-receiving surface side.
Japanese Patent Application Laid-Open Nos. 61-20371 and 61-86955 have filed applications as structures for reducing the resistance loss due to the light-receiving surface side electrode despite the use of TCO. This photovoltaic device includes a light receiving surface electrode film, a semiconductor film including a photoactive layer, a first back electrode film, an insulating film, and a second back electrode film having a lower resistance than the light receiving surface electrode film when viewed from the light incident side. The second back electrode film is overlapped with the second back electrode film by reaching the light receiving surface electrode film at a plurality of locations in the light receiving region by passing through the contact hole whose inner periphery is surrounded by the insulating film. And the light receiving surface electrode film is electrically coupled.

(C) Problems to be Solved by the Invention Incidentally, when using a photovoltaic device, it is common to adopt a structure in which a plurality of unit photoelectric conversion elements are electrically connected in series. In such a structure, the output characteristic of the photovoltaic device, that is, the ineffective region that does not contribute to power generation that adversely affects the output power includes the adjacent space between each unit photoelectric conversion element and the contact hole. this house,
The adjacent space is indispensable for forming a plurality of unit photoelectric conversion elements, and the size that can be minimized is naturally determined from the processing accuracy.

Therefore, the present invention is to optimize the size of the contact holes and the interval between the contact holes so that the maximum value can be obtained as the output power of the photovoltaic device.

(D) Means for Solving the Problems The present invention provides a light-receiving area by overlapping a light-transmitting light-receiving surface electrode film, a semiconductor film including a photoactive layer, a first back electrode film, an insulating film, and a second back electrode film. The unit photoelectric conversion element in which the second electrode film penetrates through the insulating film and is electrically coupled to the light receiving surface electrode film at a plurality of connection points in the plurality of the first photoelectric conversion elements is connected to the first back electrode film of one of the photoelectric conversion elements adjacent to each other. A photovoltaic device which is electrically connected in series by being coupled to the semiconductor film on the back side with the other second back electrode electrode film, wherein q is an elementary charge and k is a Boltzmann constant. Sometimes, the size of the connection portion and the interval between the connection portions are set to T under a predetermined condition.
(Absolute temperature), i _ph (photocurrent density), i ₀ (reverse saturation current density), R _s (series resistance), R _st (sheet resistance), R
_sh (shunt resistance) and n (n value of diode characteristics)
And the output power based on the output current calculated by the following equation is set to a value determined to be substantially maximum.

i (r) = i _ph −i ₀ [exp {q (V (r) + R _s i (r)) / nkT} −1] − (V (r) + R _s i (r)) / R _sh dV ( r) / dr = I (r) · R _st / 2πr where I _out : output current at one connection point i (r): current amount generated in a minute area at radius r point I (r): radius r Total amount of current flowing in the direction of the contact hole in the ring-shaped region at the point V (r): Voltage at radius r R: Radius of a circle having the same area as a square corresponding to the arrangement interval of connection points R ₀ : Radius of connection point (E) Function According to the present invention, the size of the connection portion between the second back electrode film and the light receiving surface electrode film and the interval between the connection portions are set to approximately the maximum value based on the output current calculated by a predetermined relational expression. The photovoltaic device optimized with the value determined as possible and having excellent output characteristics can be obtained.

(F) Embodiment FIG. 1 is a partial cross-sectional perspective view of a main part of a first embodiment of a photovoltaic device of the present invention viewed obliquely from the back side with respect to the light incident direction. As shown, a transmissive light-receiving surface electrode film such as TCO (1), a semiconductor film mainly composed of amorphous silicon including a photoactive layer of a semiconductor junction such as a pin junction and a pn junction parallel to the film surface (2), ohmic A first back electrode film (3) made of metal, an insulating film (4), and a second back electrode film (5) made of a metal having lower resistance than the light receiving surface electrode film (1) are superimposed to form a second back electrode. The film (5) penetrates the insulating film (4), the first back electrode film (3) and the semiconductor film (2) at a plurality of locations in the light receiving region, and the inner periphery is surrounded by the insulating film (4). By reaching the light-receiving surface electrode film (1) through the circular contact hole (6), the light-receiving surface electrode film (1) is electrically connected to the light-receiving surface electrode film (1). A plurality of unit photovoltaic bound to (SC
₁ ) (SC ₂ ) (SC ₃ ) ... is replaced by each unit photoelectric conversion element (SC ₁ )
The light receiving surface electrode films (1) of (SC ₂ ) and (SC ₃ ) are provided on a translucent insulating substrate (7) such as glass serving as a support and a light receiving surface protector with a separation distance d. I have.

Then, each unit photoelectric conversion element (SC ₁ ) (SC ₂ ) (SC ₃ )
The light-receiving surface electrode film (1) and the first back electrode film (3) of the element adjacent to each other are connected to each photoelectric conversion element (SC ₁ ) (SC ₂ ) (SC ₃ ).
The first back electrode film (in the portion opened by performing, for example, laser beam irradiation or etching) on the back surface side of the semiconductor film (2) from the side of the insulating film (4) without directly overlapping in the adjacent space portion of 3), the second back electrode film (5) of the adjacent element extends and is buried, so that the adjacent unit photoelectric conversion elements (SC ₁ ) (SC ₂ ) (SC ₃ )
Are electrically connected in series.

By the way, what is important in the photovoltaic device having such a structure is the size of the contact holes (6) and the arrangement intervals thereof. When the size of the contact hole (6) is reduced, the ineffective area in the light receiving region is also reduced, but the workability and workability are poor, and when the contact hole (6) is further reduced, the current collecting contact hole is formed. Since the contact resistance between the light receiving surface electrode film (1) and the second back electrode film (5) at the center of (6) is increased, the resistance loss is not reduced.

On the other hand, if the number of contact holes (6) is increased to facilitate workability and workability, the larger the number, the larger the ineffective area in the light receiving region. The current collecting effect is reduced, and the resistance loss in the light receiving surface electrode film (1) cannot be sufficiently suppressed.

That is, in the photovoltaic device as described above, when obtaining the maximum output, it is considered that there are optimal values for the size of the contact holes (6) and the interval between the contact holes.

Therefore, in the present invention, the size of the contact holes (6) and their arrangement intervals (the arrangement intervals correspond to the number of the contact holes (6) and, in other words, the effective areas of the light receiving regions) are determined. The output current in the contact hole (6) was calculated, and the output power based on this was considered.

FIG. 2 is an enlarged cross-sectional view of the contact hole (6), and the current collected by each contact hole (6) is generated inside a circle having a radius R. This circle is drawn around the contact hole (6) so as to be in contact with each other around each contact hole (6) and to have the same area as a square defined by the same area. Is also automatically determined.

The first expression below shows an output current I _out in one contact hole (6).

However, in the above equation, R: radius of a circle having the same area as the square corresponding to the arrangement interval of the contact holes (6) R0: radius of the contact holes (6) i (r): generated in a small area at a radius r point Current Amount The current amount i (r) is obtained by the following equations (2) and (3).

Where i _ph : photocurrent density i ₀ : reverse saturation current density v (r): voltage at radius r R _s : series resistance R _sh : shunt resistance n: n value of diode characteristics q: elementary charge k: Boltzmann's constant T: absolute temperature R _st : sheet resistance I (r): total amount of current flowing in the direction of the contact hole (6) in the ring-shaped region at radius r where q and k are constants, and T, i _ph , i ₀ , R _s , R _st , R _sh ,
And n may be values obtained under predetermined conditions. The predetermined condition may be any condition, for example, a standard measurement condition (AM) of a solar cell described in a known latest photovoltaic power generation technology (issued on July 1, 1984, Maki Shoten, p. 143).
1.5, 100 mW / cm ² , 28 ° C.).

FIG. 3 shows a contact hole (6) using the above equations.
FIG. 4 is a characteristic diagram showing a relationship between a maximum output of the photovoltaic device and a ratio of an effective area, using a radius R0 of the parameter as a parameter. The photovoltaic device in the figure is a photoelectric conversion element (SC ₁ ) (S
C ₂ ) (SC ₃ ) ... are 10 cm × 10 cm in size with 10 adjacent spaces of 0.15 mm, and therefore, 98.5%
Of the effective area. Also, in FIG.
The mark indicates the case where the radius of the contact hole (6) is 0.10 mm, the mark ○ indicates 0.15 mm, the mark Δ indicates 0.25 mm, and the mark □ indicates
Each case of 0.55 mm is shown.

As can be seen from the figure, the radius of the contact hole (6) is 0.10
In the case of mm, the maximum output is large up to 98% of the effective area ratio. On the other hand, the radius of the contact hole (6) is 0.15m
In the case of m, 0.25 mm and 0.55 mm, the maximum output does not increase as the ratio of the effective area increases. When the radius of the contact hole (6) is 0.15 mm and 0.25 mm, the ratio of the effective area is 97.5 mm. %, The maximum output is obtained when the radius of the contact hole (6) is 0.55 mm, and the maximum output is obtained when the ratio of the effective area is 96.3%.

In this way, in the present invention, the radius and the number of the contact holes (6), that is, the ratio of the effective area, can be appropriately optimized by the calculation using the above three equations.

On the other hand, FIG. 4 is a characteristic diagram showing the relationship between the maximum output of the photovoltaic device and the ratio of the effective area with the sheet resistance R _st of the light receiving surface electrode film (1) as a parameter using the above equations. . The radius of the contact hole (6) of the photovoltaic device used in the figure is 0.25 mm.
The mark indicates the case where the sheet resistance of the light receiving surface electrode film (1) is 10Ω / □, the mark ○ indicates 30Ω / □, and the mark Δ indicates 50Ω / □.
□ and □ indicate the case of 100Ω / □, respectively.

As can be seen from the figure, there is an optimal number of contact holes (6) at which the maximum output can be obtained according to the sheet resistance of the light receiving surface electrode film (1), that is, the ratio of the effective area. ) Sheet resistance of 10Ω / □, 30Ω / □, 50Ω respectively
/ □ and 100Ω / □, the optimal effective area ratio is 9
It can be seen that they are 7.5%, 96.5%, 96% and 95.5%.

Even in this case, by performing the calculation using the above three equations, the radius and the number of the contact holes (6), that is, the effective area of the contact holes (6) are determined according to the sheet resistance of the light receiving surface electrode film (1). The ratio can be appropriately set to an optimal state.

FIG. 5 is a partial cross-sectional perspective view of a main part of a second embodiment of the photovoltaic device of the present invention viewed obliquely from the rear side with respect to the light incident direction.

This embodiment is characterized in that the light incident direction is reversed as compared with the previous embodiment. That is, an insulating substrate (70) made of a metal plate (71) such as stainless steel or an aluminum plate having an insulating film (72) such as an enameled or sealed alumina film on the surface is prepared. A metal second back electrode film (5) is divided and arranged for each of the elements (SC ₁ ) (SC ₂ ) (SC ₃ )... Then, an insulating film (4), a first back electrode film (3), and at least one A semiconductor film (2) including a photoactive layer having a semiconductor junction and a light-transmitting light-receiving surface electrode film (1) such as TCO are laminated. At this time, the insulating film (4) is divided for each element (SC ₁ ) (SC ₂ ) (SC ₃ ).
A first back electrode film (3) of an adjacent element is bonded to the back electrode film (5). Semiconductor film (2), first back electrode film (3)
A contact hole (6) reaching the second back electrode film (5) at a plurality of positions in the light receiving region is formed in the insulating film (4) as in the first embodiment, and the inner wall of the contact hole (6) is It is covered with the insulating film (4). By burying the contact hole (6) with the light-receiving surface electrode film (1), the light-receiving surface electrode film (1) and the second back electrode film (5) are electrically coupled with each other, and The photoelectric conversion elements (SC ₁ ) (SC ₂ ) (SC ₃ ) are electrically connected in series on the back surface of the semiconductor film (2).

In the photovoltaic device having this structure, the size and number of the contact holes (6) are the same as in the first embodiment.
It is natural that the output current in the contact hole (6) is calculated based on the above three equations, and the output current based on the calculated output current is set to a value determined to be substantially maximum.

In addition, each contact hole (6) is not limited to the circular shape as described above, but may be an arbitrary shape such as a square. In this case, for example, the current collected by each of the square contact holes (6) is a current generated in a square that is in contact with each other with each contact hole (6) as a center and divided by the same area. Therefore, the size of the contact hole (6) and the interval between the contact holes are determined by calculating the current generated in the square.

(G) Effects of the Invention According to the present invention, a light-transmitting light-receiving surface electrode film, a semiconductor film including a photoactive layer, a first back electrode film, an insulating film, and a second back electrode film are superimposed on each other to form a light-receiving region. A unit photoelectric conversion element, in which the second back electrode film penetrates through the insulating film and is electrically coupled to the light receiving surface electrode film at a plurality of connection points, is connected to one of the first back electrode films of adjacent photoelectric conversion elements. A photovoltaic device which is electrically connected in series by being coupled to the semiconductor film on the back side with the other second back electrode film, wherein the size of the connection portion and the arrangement interval are predetermined. By setting the output power based on the output current calculated by the following formula to be a value determined to be substantially maximum, the state of the connection point has been optimized, so that the optimum output characteristics according to the workability and workability. To provide a photovoltaic device having Can be.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional perspective view showing a main part of a first embodiment of the present invention, FIG. 2 is a cross-sectional view further showing the main part, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the maximum output of the photovoltaic device as a parameter and the ratio of the effective area, and FIG. 4 shows the ratio of the maximum output and the effective area of the photovoltaic device with the sheet resistance of the light receiving surface electrode film as a parameter. FIG. 5 is a partial sectional perspective view showing a main part of the second embodiment of the present invention. (1) ... light-receiving surface electrode film, (2) ... semiconductor film, (3)
... first back electrode film, (4) ... insulating film, (5) ... second back electrode film, (6) ... contact hole.

Claims (1)

(57) [Claims] 1. A light-transmitting light-receiving surface electrode film, a semiconductor film including a photoactive layer, a first back electrode film, an insulating film, and a second back electrode film are superimposed on each other, and the first and second back electrode films are formed at a plurality of connection locations in a light-receiving region. A unit photoelectric conversion element in which a two-electrode film penetrates through the insulating film and is electrically coupled to a light-receiving surface electrode film is formed by combining one of the first and second back electrode films of adjacent photoelectric conversion elements with the other. A photovoltaic device electrically connected in series by being coupled to the semiconductor film on the back side, and when q is an elementary charge and k is a Boltzmann constant, the size of the connection portion and The arrangement intervals are defined as T (absolute temperature), i _ph (photocurrent density), i ₀ (reverse saturation current density), R _s (series resistance), R _st (sheet resistance) under predetermined conditions, R _sh (shunt resistor), and using the values of n (n values of the diode characteristic) by the following equation Photovoltaic device, characterized in that the output power based on the output current to be calculated is the possible value determined substantially maximum. i (r) = i _ph −i ₀ [exp {q (V (r) + R _s i (r)) / nkT} −1] − (V (r) + R _s i (r)) / R _sh dV ( r) / dr = I (r) · R _st / 2πr where I _out : output current at one connection point i (r): current amount generated in a minute area at radius r point I (r): radius r Total amount of current flowing in the direction of the contact hole in the ring-shaped region at the point V (r): Voltage at radius r R: Radius of a circle having the same area as a square corresponding to the arrangement interval of connection points R ₀ : Radius of connection point