Amorphous semiconductor materials

摘要

Wide band gap p-type amorphous silicon alloys having increased conductivities contain oxygen as a band gap increasing element. Other band gap increasing elements such as carbon can also be incorporated in minor amounts. The alloys also incorporate at least one density of states reducing element such a fluorine and/or hydrogen. The compensating or altering element and other elements such as a p-type dopant boron can be added during deposition by glow discharge decomposition. Incorporation of oxygen in concentrations of one to thirty percent results in band gaps of 1.7eV to greater than 2.0eV. For a given band gap, the present alloys exhibit conductivities substantially greater than prior wide band gap p amorphous silicon alloys incorporating carbon alone as a band gap increasing element. The wide band gap p amorphous silicon alloys are particularly useful in photoresponsive devices. A p-i-n photovoltaic cell comprises a back reflector 114, a wideband gap P+ type layer 116, a thick intrinsic layer 118 and an N+ type layer 120 topped with a transparent conductive oxide 122; a grid electrode 124 and an antireflection layer 126. Bandgap reducing elements such as Ge, Sn, or Pb may be incorporated in the intrinsic layer 118 and a graded bandgap structure may be produced. The positions of the P+ and N+ type layers may be intercharged (Fig. 5) and a pair of cells may be stacked in a tandem configuration (Fig. 6).