Photoelectric conversion device and method for producing same

#The present invention relates to a photoelectric conversion device and a method for producing the same.

#A solar cell made from polycrystalline silicon, microcrystalline silicon or amorphous silicon is well known. Especially, with respect to resource consumption and from the viewpoint that a reduction in costs and an increase in efficiency is desirable, the focus has been on a photoelectric conversion device having a laminated structure composed of microcrystalline silicon or amorphous silicon thin films.

#Generally, a photoelectric conversion device is produced by laminating, on the insulating surface of a substrate, a first electrode, one or more semiconductor thin film photoelectric conversion cells, and a second electrode, in the stated order. The individual photoelectric conversion units for the device are formed by laminating a p-type layer, an i-type layer and an n-type layer, beginning on the light incidence side. A well known method for increasing the conversion efficiency of the photoelectric conversion device is the stacking of two or more types of photoelectric conversion cells in the direction of the incidence of light. For the photoelectric conversion device, a first photoelectric conversion unit, which includes a photoelectric conversion layer having a large bandgap, is arranged on the light incidence side, and behind this unit, a second photoelectric conversion unit is arranged that includes a photoelectric conversion layer having a bandgap narrower than that of the first photoelectric conversion unit. With this arrangement, photoelectric conversion can be performed for a wide wavelength range of incident light, and an overall increase in the conversion efficiency is obtained for the device. For example, a structure is well known wherein an amorphous silicon (a-Si) photoelectric conversion unit is employed as a top cell and a microcrystalline silicon (μc-Si) photoelectric conversion unit is employed as a bottom cell. Above all, attention has been drawn to a structure wherein amorphous silicon and microcrystalline silicon are deposited in the stated order, on a translucent substrate, and light is permitted to enter and impinge on the substrate face, and with this structure, an integrated large-area module can be easily provided and the size of the area of the translucent substrate that does not contribute to photoelectric conversion can be reduced.

#FIG. 1 is a diagram illustrating the structure of a photoelectric conversion device according to one embodiment of the present invention.

#FIG. 2 is a diagram illustrating the structure of the μc-Si unit of the photoelectric conversion device according to the embodiment of the present invention.

#FIG. 3 is a diagram illustrating the structure of the μc-Si unit of the photoelectric conversion device according to the embodiment of the present invention.

#FIG. 1 is a cross-sectional view of the structure of a photoelectric conversion device 100 according to one embodiment of the present invention. The photoelectric conversion device 100 of this embodiment has a structure provided by laminating, in order, beginning at the side of a transparent insulating substrate 10, which is the light incidence side, a transparent conductive film 12, an amorphous silicon (a-Si) (photoelectric conversion) unit 102, which is a top cell having a large bandgap, an intermediate layer 14, a microcrystalline silicon (μc-Si) (photoelectric conversion) unit 104, which is a bottom cell having a smaller bandgap than the a-Si unit 102, a first back-contact electrode layer 16, a second back-contact electrode layer 18, a filling material 20 and a protective layer 22.

#The structure of the photoelectric conversion device 100 and a method for producing this device will now be described for the embodiment of the present invention.

#For the transparent insulating substrate 10, a material, such as a glass substrate or a plastic substrate, that is optically transparent at least within the wavelength range of visible light, can be employed. The transparent conductive film 12 is deposited on the transparent insulating substrate 10. It is appropriate for the transparent conductive film 12 to be provided by employing at least one of transparent conductive oxides (TCO), such as stannic oxide (SnO2), zinc oxide (ZnO) and indium tin oxide (ITO) doped with tin (Sn), antimony (Sb), fluorine (F), aluminum (Al), etc. Especially, zinc oxide (ZnO) is appropriate because the optical transmittance is high, the electrical resistivity is low and the plasma resistivity is superior. The transparent conductive film 12 can be formed by using sputtering, for example. The appropriate range for the film thickness of the transparent conductive film 12 can be from equal to or greater than 0.5 μm to equal to or smaller than 5 μm. Further, it is preferable that the surface of the transparent conductive film 12 be uneven, so as to provide light confinement effects.