Photovoltaic device

[Detailed Description of the Invention]

(b) Field of the Invention The present invention relates to photovoltaic devices, such as a solar cell and a photosensor. (Ro) PRIOR ART In recent years, the photovoltaic device consisting of amorphous silicon is widely used as the power supply for calculators, a power supply for small independent, etc. Material called especially amorphous silicon also in this amorphous silicon, It has come to be widely put in practical use from that the manufacturing method is suitable for formation of a large area as compared with the conventional single crystal silicon, there being little amount of the material used and ending by harnessing the feature in the physical-properties side of the big optical absorption coefficient further, etc. However, it waits for the appearance of the photovoltaic device in which conversion efficiency is still larger than the present in view of an energy situation in recent years, global environment problems, etc. It is necessary to take out efficiently the optical generation career which was absorbed in the photoelectric conversion layer in a photovoltaic device, without leaving the light which generally did :incidence of this conversion efficiency for making it high, and occurred within the above-mentioned layer by this absorption to the exterior of the device. In order to use especially the above-mentioned incidence light effectively, it is necessary to leak and to absorb each wavelength light contained in the incidence light. In order to achieve this object, with the photovoltaic device consisting of the semiconductor layer and back electrode as a transparent conductive film and a power generation layer, detailed concavo-convex shape is conventionally formed in the surface of the above-mentioned transparent conductive film located in the above-mentioned semiconductor layer side by performing a surface treatment. Thereby, it becomes possible to make absorption of the long wavelength light which is reflected within the above-mentioned photovoltaic device many times, and is contained in the incidence light as a result increase effectually of the above-mentioned incidence light. As the method of the above-mentioned surface treatment, the membrane formation conditions of the above-mentioned transparent conductive film are controlled suitably, The above-mentioned transparent conductive film is formed in comparatively flat shape what attaches concavo-convex shape to the surface of the above-mentioned transparent conductive film itself, and at the beginning, and there are some which form concavo-convex shape in the surface by etching by an after that, for example, chemicals, solvent etc. As mentioned above, the transparent conductive film which has concavo-convex shape on the surface is conventionally called the texture transparent conductive film, and suppose that this term is used for below. (C) In the photovoltaic device possessing the Division above-mentioned texture transparent conductive film which an invention tends to solve, especially absorption of the long wavelength light contained in incidence light as mentioned above improves. About this improvement in the characteristic, it can check as an increase in the short circuit photoelectric current of a photovoltaic device. however -- the above-mentioned photovoltaic device -- Such -- while the improvement [ like ] in the characteristic could be achieved, the fall phenomenon of the open voltage by using the above-mentioned texture transparent conductive film had occurred simultaneously. This problem has occurred, when the above-mentioned texture transparent conductive film is used conventionally, but it is overlooked from the increase in the above-mentioned short circuit photoelectric current having been large enough to the fall of the above-mentioned open voltage. However, since the above-mentioned open voltage is deeply related to the design of the system driven with the photovoltaic device, solution of the above-mentioned fall phenomenon is important. Although conventionally known about the above-mentioned fall phenomenon of open voltage based on the above-mentioned texture transparent conductive film, it was not clarified about the cause until now. being related with these contents -- Japanese Journal of Applied Physics Vol, 28 No, 3.March, and 1989. -- it is indicated in detail to the 311st page thru/or the 315th page. This artificer made this cause clear from a series of researches. After Drawing 5 forms a transparent conductive film on a substrate, it is a characteristic figure of the photovoltaic device which made the amorphous silicon which comprises the layered product of p layer, i layer, and n layer the power generation layer, and shows the relation between the membrane formation time of the above-mentioned p layer, and the open voltage of the photovoltaic device. As a method for film deposition of the above-mentioned amorphous silicon, the well-known plasma CVD method was adopted conventionally. The horizontal axis of the figure is the membrane formation time of an account of gate p layer, and generally, it is thought that the film thickness of the p layer becomes thick almost linearly as the time becomes long. The vertical axis shows the open voltage of the photovoltaic device. It inquired using two kinds of things as a photovoltaic device. The difference is in the surface state of the transparent conductive film currently used, and other elements are completely the same. The surface state of one side is almost flat. Another side is conventionally based on a well-known formation method, and makes the surface concavo-convex shape. Below, the photovoltaic device which uses the former transparent conductive film is called the 2nd device, and it of the 1st device and the latter is explained for it in full detail. In the 2nd above-mentioned device, when it compares in same membrane formation time, the open voltage is smaller than the 1st above-mentioned device, and the difference becomes so large that the above-mentioned membrane formation time is short. This artificer was based on this result and measured the film thickness of each p layer about the two above-mentioned kinds of photovoltaic devices. As film thickness, it measured about the 2-way at that time. Drawing 6 is a schematic cross section for explaining this direction. (7) is a supporting board, (8) is a texture transparent conductive film, and (9) is the above-mentioned p layer of the amorphous silicon formed on the texture transparent conductive film (8). As A of the figure shows, one of the above-mentioned 2-ways is equivalent to film thickness currently generally used from the former, and it says thickness of a film which can be perpendicularly set to the principal surface of the above-mentioned substrate (7) where a film is formed. B of another side says thickness of a film to a perpendicular direction of the surface of the above-mentioned transparent conductive film. Here, in order to explain easily, the former is called film thickness A and the latter is called film thickness B. Therefore, in p layer in the 1st above-mentioned device, since it is formed on the flat transparent conductive film, the perpendicular direction of the surface of the transparent conductive film and the perpendicular direction of the principal surface of the above-mentioned substrate turn into the same direction in general, and film thickness A of the p layer and their film thickness B will correspond. On the other hand, since the surface of the above-mentioned transparent conductive film is concavo-convex shape in the case of the above-mentioned texture transparent conductive film, it will differ from the perpendicular direction of the surface of the above-mentioned transparent conductive film, and the perpendicular direction of the principal surface of the above-mentioned substrate. Therefore, it will measure about the thickness of the film of a different direction from film thickness A and film thickness B. Then, the film thickness of p layer in the 1st and 2nd above-mentioned devices at the time of carrying out the above-mentioned membrane formation time of p layer of the above-mentioned amorphous silicon for 5 minutes was measured. the 1st device -- both film thickness A and film thickness B -- although -- to having been about 130 persons, although it was about 130 persons about film thickness A, about film thickness B, it turned out [ about 100 persons and ] that it is thin with the photovoltaic device which has a texture transparent conductive film, i.e., the 2nd device. From the above measurement result, this artificer traced that the cause of the above-mentioned fall phenomenon of open voltage was what is depended on a texture transparent conductive film at the thinness of film thickness B of an at To p layer. The place made into this reason is because the internal electric field as pn junction constituted with the above-mentioned amorphous silicon becomes weak and is considered to have caused the fall of open voltage as a result, when film thickness B becomes thin. This serves as a big subject in the photovoltaic device which uses a texture transparent conductive film. Because, if the above-mentioned film thickness B is thickly carried out to the above-mentioned open voltage being made to only improve, namely, the above-mentioned membrane formation time is lengthened, the above-mentioned film thickness A will be thickened simultaneously, and will cause the fall of the short circuit photoelectric current of the above-mentioned photovoltaic device as a result. That is, the increase in film thickness of the above-mentioned p layer is for eventually making the sensitivity to the short wavelength light of the incidence lights fall. In the photovoltaic device which adopted the above-mentioned texture transparent conductive film, there is a place made into the object of the present invention since it is such in providing the photovoltaic device which also realizes improvement in a short-circuit current simultaneously while controlling the fall of the above-mentioned open voltage. (D) Place by which it is characterized [ of the means present invention photovoltaic device for solving a subject ], In the surface by the side of the above-mentioned semiconductor film of the above-mentioned light transmission electric conduction film, it is in the photovoltaic device which covering formation of the semiconductor film which has a light transmission electric conduction film and optical sensitivity is carried out, and changes on the principal surface of a substrate, While the concavo-convex shape which has a convex part of the shape of a truncated pyramid or a pyramid is established, It is in the crossed axes angle of the ridgeline of the above-mentioned truncated pyramid or a pyramid and the altitude of the above-mentioned principal surface to accomplish having taken 30 degrees or more for 60 degrees or less, and the height of the perpendicular above-mentioned truncated pyramid or pyramid having carried out to the above-mentioned principal surface in more than 1000A and below 3000A. (Ho) OPERATION While much detailed concavo-convex shape is established on the above-mentioned substrate and the convex part has the shape of a truncated pyramid or a pyramid among the concavo-convex shape, By forming so that the crossed axes angle which the ridgeline of the truncated pyramid or a pyramid and the altitude of the principal surface of the above-mentioned substrate constitute may be 60 degrees or less 30 degrees or more, it becomes possible to make the difference of film thickness A of p layer and film thickness B on the texture transparent conductive film mentioned above decrease, and it can control the fall of open voltage. In order that adopting the shape of the above-mentioned truncated pyramid or a pyramid may reduce the grade of unevenness of the above-mentioned light transmission electric conduction film, in a darn state, the fall of the short circuit photoelectric current as a photovoltaic device arises. then, to the above-mentioned principal surface, by forming the height of the perpendicular above-mentioned angle # stand or pyramid so that more than 1000A and below 3000A may become, dispersion of the light which entered into the photovoltaic device concerned will improve, and fall control of the above-mentioned open voltage, simultaneously improvement in the above-mentioned short circuit photoelectric current can be attained. (What) EXAMPLE Drawing 1 is an element construction drawing for describing one example of a present invention photovoltaic device. A light transmission electric conduction film with the substrate to which (1) in a figure changes from glass etc., and the concavo-convex shape whose (2) is the feature of the present invention, The semiconductor film in which (3) has optical sensitivity, and (4) are back electrodes which consist of metal membranes etc., and since especially a semiconductor film (3) makes it into a photoelectric conversion layer, they consist of the p-type semiconductor layer of (3a), the buffer layer of (3b), an i type semiconductor layer of (3c), and an n-type semiconductor layer of (3d). It is formerly a well-known thing in a photovoltaic device among these except a light transmission electric conduction film (2). Below, in accordance with an example, a light transmission electric conduction film (2) is explained in full detail. In manufacture of the above-mentioned photovoltaic device, first, a substrate (1) is arranged to a heat CVD device, and it sets to the range of 350~550-degreeC as substrate temperature. Next, it mixes with S n CI 4 by which babbling was carried out with nitrogen gas by the flow which shows oxygen gas, CF, and Br gas in the 1st table, and SnO which has concavo-convex shape, and a film are formed in the surface by passing it on the surface of a substrate (1). Since these concavo-convex shape is SnO and a thing resulting from a membranous crystal grain, the convex part serves as shape of the truncated pyramid which makes a base a polygon, or a pyramid. In the SnO2 film concerned, it becomes possible to change arbitrarily the angle and height of an oblique side of the trapezoid or triangle which is these shape, especially section-shaped [ such ] by controlling the formation conditions mentioned above. 1st Table Next, a semiconductor film (3) is conventionally formed with a well-known plasma CVD method. And finally metal membranes, such as aluminum, are formed as a back electrode (4), and it completes. Next, correlation with a crossed axes angle with the altitude of the principal surface of the substrate (1) which the above-mentioned truncated pyramid of an at The light transmission electric conduction film (2) or the ridgeline of a pyramid makes to an example photovoltaic device, and the characteristic of the photovoltaic device is explained. Drawing 2 is a mimetic diagram for explaining the above-mentioned crossed axes angle, and Drawing 3 is a characteristic figure showing the relation between the above-mentioned crossed axes angle, and the conversion efficiency of the above-mentioned photovoltaic device and open voltage. The irradiation conditions of light are AMl and 5.100+nW/cm'. It is an altitude [ as opposed to / as opposed to / in (5) shown in Drawing 2 / the ridgeline of the convex part of a light transmission electric conduction film (2) / the surface of a substrate (1) in (6) ]. The above-mentioned crossed axes angle said here is an angle which is shown by alpha and which is made by a ridgeline (5) and the altitude (6). As shown in Drawing 3, by making the above-mentioned crossed axes angle into 30 degrees or more, the above-mentioned open voltage improves remarkably and above-mentioned conversion efficiency's is improving greatly in connection with it. on the other hand, even if it enlarges the above-mentioned crossed axes angle further, the above-mentioned conversion efficiency decreases gently in spite of the above-mentioned open voltage being about 1 law. This is for short circuit photoelectric current to decrease by increase of the above-mentioned crossed axes angle, and conversion efficiency is falling as a whole. Therefore, in a present invention photovoltaic device, it is preferred to make the above-mentioned crossed axes angle into 60 degrees or less 30 degrees or more practically. When the above-mentioned crossed axes angle is made into 35 degrees as SnO of this range, and formation conditions for membranous, for example, Substrate temperature is set to 500 degreeC and it is 0.7 0(g/m 1n). gas about S n CI s 0.4 (1/m 1n) It can manufacture by carrying out CF and B r gas 0.5-3 (1/m 1n). Next, correlation with the height which the above-mentioned truncated pyramid or a pyramid makes, and the characteristic of a photovoltaic device is explained in full detail. The above-mentioned height said here is the distance of the above-mentioned truncated pyramid or the highest part of a pyramid to the perpendicular direction of the above-mentioned substrate, and the minimum part. Drawing 4 is a characteristic figure showing the relation between the above-mentioned height, and conversion efficiency and open voltage. The above-mentioned crossed axes angle of the photovoltaic device concerned is 35 degrees, and the irradiation conditions of light are AMl and sl 100mW/cm." According to the figure, in respect of open voltage, all show the big value to within the limits whose above-mentioned height is 500~3500 persons. if the above-mentioned height is made smaller than 1000 persons about conversion efficiency on the other hand -- a case -- the value -- rapid -- falling . If more than 3000A is used, the value will decrease gradually. In the field in which the diffused reflection of incidence light becomes the above-mentioned concavo-convex shape is weak, and insufficient [ this cause ] in the field where the above-mentioned height is small, and the value of short circuit photoelectric current becomes small and where the above-mentioned height is large on the other hand, The above-mentioned amorphous silicon etc. cannot fully form on a light transmission electric conduction film from it being a thin film, but it is Drawing 3 overall after all of Special. It is for Sexual power-ization to arise. Therefore, it is preferred to make the above-mentioned height into the range more than 1000A and below 3000A. (1-) EFFECT OF THE INVENTION According to the present invention photovoltaic device, even if it adopts the light transmission electric conduction film which has detailed concavo-convex shape, it becomes possible to make short circuit photoelectric current improve, without reducing the open voltage value of the photovoltaic device.

[Brief Description of the Drawings]

A schematic cross section for Drawing 1 to illustrate the element tectonic profile of a present invention photovoltaic device, and for Drawing 2 illustrate a crossed axes angle and Drawing 3 are the conversion efficiency of the above-mentioned photovoltaic device, and open voltage, The characteristic figure showing a relation with the above-mentioned crossed axes angle, the characteristic figure in which Drawing 4 shows the relation between the conversion efficiency of the above-mentioned photovoltaic device and open voltage, and the above-mentioned height, the characteristic figure in which Drawing 5 shows the relation between the membrane formation time of p layer and the open voltage of a photovoltaic device, and Drawing 6 are schematic cross sections for explaining the direction of film thickness.