DEFECT STUDY IN AMORPHOUS-SILICON CRYSTALLINE SILICON SOLAR-CELLS BY THERMALLY STIMULATED CAPACITANCE

Interface traps created by amorphous silicon (a-Si) deposition using d e magnetron sputtering or a microwave plasma-enhanced chemical vapor d eposition method onto p-type crystalline silicon (c-Si) substrates in solar cell structures were studied by thermally stimulated capacitance . The trap properties (type, energy, and concentration) have been esti mated as a function of various cell fabrication conditions. Plasma dep osition of a-Si is seen to induce electron traps when the c-Si substra tes are pretreated with hydrofluoric acid, and hole traps when a thin oxide layer is initially present on the c-Si. A strong correlation is observed between the trap activation energies when electron trapping c enters are present and the corresponding photoresponse of these solar cells. Solar cells with 10% efficiency fabricated by a-Si sputtered at 64 W of power, exhibit 3 x 10(14) cm(-3) trapping centers with an act ivation energy of 0.44 eV. (C) 1997 American institute of Physics.