Photovoltaic device having incident radiation directing means for total

Abstract

There is disclosed new and improved photovoltaic devices which provide increased short circuit currents and efficiencies over that previously obtainable from prior devices. The disclosed devices include incident radiation directing means for directing at least a portion of the incident light through the active region or regions thereof at angles sufficient to substantially confine the directed radiation in the devices. This allows substantially total utilization of photogenerated electron-hole pairs. Further, because the light is directed through the active region or regions at such angles, the active regions can be made thinner to also increase collection efficiencies. The incident radiation directors can be random surface or bulk reflectors to provide random scattering of the light, or periodic surface or bulk reflector to provide selective scattering of the light. While the present invention is applicable to photovoltaic devices formed from any type of semiconductor material, as for example, crystalline, polycrystalline, or amorphous semiconductor alloys or any combination thereof, disclosure herein is primarily directed to photovoltaic devices formed from amorphous silicon alloys preferably incorporating fluorine as a density of states reducing element. The disclosure is also directed to, without limitation, photovoltaic devices of the p-i-n configuration, both as single cells and multiple cells arranged in tandem.