Defect study in amorphous silicon/crystalline silicon solar cells by thermally stimulated capacitance

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Abstract
Interface traps created by amorphous silicon (a- Si ) deposition using dc magnetron sputtering or a microwave plasma-enhanced chemical vapor deposition method onto p -type crystalline silicon (c- Si ) substrates in solar cellstructures were studied by thermally stimulated capacitance. The trap properties (type, energy, and concentration) have been estimated as a function of various cell fabrication conditions. Plasma deposition of a- Si is seen to induce electron traps when the c- Si substrates 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 centers 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 3×10 14 cm −3 trapping centers with an activation energy of 0.44 eV.