High efficiency thin-film multiple-gap photovoltaic device
First Claim
1. In a thin-film multiple-gap photovoltaic device having an opaque electrical contact and a transparent electrical contact with a first cell and a second cell therebetween and with the first cell being adjacent the transparent electrical contact and the second cell being adjacent the opaque electrical contact, each of the cells having a junction layer and a base layer and an electrical junction therebetween and each base layer comprising a base region and an intermediate region with the intermediate region being adjacent the electrical junction layer, the improvement being each of said cells being made from semiconductor materials selected from Group IV elements and their alloys in the amorphous state, said first cell having a higher bandgap than the bandgap of said second cell, and an optically transparent amorphous semiconductor buffer layer of the same conductivity type as the conductivity type of the junction layer of said second cell between said first cell and said second cell for connecting said cells together.
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Abstract
A photovoltaic device includes at least two solar cells made from Group IV elements or their alloys in the amorphous state mounted on a substrate. The outermost or first cell has a larger bandgap than the second cell. Various techniques are utilized to improve the efficiency of the device.
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Citations
30 Claims
- 1. In a thin-film multiple-gap photovoltaic device having an opaque electrical contact and a transparent electrical contact with a first cell and a second cell therebetween and with the first cell being adjacent the transparent electrical contact and the second cell being adjacent the opaque electrical contact, each of the cells having a junction layer and a base layer and an electrical junction therebetween and each base layer comprising a base region and an intermediate region with the intermediate region being adjacent the electrical junction layer, the improvement being each of said cells being made from semiconductor materials selected from Group IV elements and their alloys in the amorphous state, said first cell having a higher bandgap than the bandgap of said second cell, and an optically transparent amorphous semiconductor buffer layer of the same conductivity type as the conductivity type of the junction layer of said second cell between said first cell and said second cell for connecting said cells together.
- 19. In a method of making a thin-film multiple-gap photovoltaic device wherein a first cell is formed on a second cell which is formed on an opaque electrical contact with a transparent electrical contact being formed on the first cell and wherein each cell includes a junction layer and a base layer with an electrical junction therebetween and with each base layer having a base region and an intermediate region, the improvement being forming each of said cells from semiconductor materials selected from Group IV elements and their alloys in the amorphous state, forming the first cell with a higher bandgap than the bandgap of the second cell, forming an optically transparent amorphous semiconductor buffer layer between the first cell and the second cell with the buffer layer having the same conductivity type as the conductivity type of the junction layer of the second cell and with the buffer layer having a bandgap higher than the bandgap of the second cell, and heavily doping the base region of the first cell and the junction layer of the second cell.
Specification