Polycrystalline or amorphous semiconductor photovoltaic device having improved collection efficiency

Claim 1

A photovoltaic device comprising: a body of polycrystalline or amorphous semiconductor material capable of generating carriers by the absorption of solar radiation having first and second opposed surfaces and including therein a first layer of one conductivity type along the first surface, a second layer of the same conductivity type as said first layer along the second surface and a third layer between and contiguous to both first and second layers, said third layer being of a conductivity type opposite the conductivity type of said first and second layers so as to form a first P-N junction between said first and third layers and a second P-N junction between said second and third layers, said third layer being of a thickness, from said first P-N junction to said second P-N junction, of at least about twice the minority carrier diffusion length of the semiconductor material of said body; a first pocket region at said first surface and extending as far as the first P-N junction, said first pocket region being of the same conductivity type as said third layer but of a higher concentration; means for electrically connecting the first and second P-N junctions; and means for both electrically contacting said second layer at said second surface and reflecting solar radiation unabsorbed by said body back into said body.