Cerium oxide and hydrogen co-doped indium oxide films for high-efficiency silicon heterojunction solar cells

CeO2 and hydrogen co-doped In2O3 (ICO:H) films deposited by ion plating with dc arc-discharge were used as a transparent conducting oxide (TCO) electrode in hydrogenated amorphous silicon (a-Si:H)/crystalline silicon (c-Si) heterojunction (SHJ) solar cells. Incorporating ICO:H instead of conventional Sn-doped In2O3 (ITO) films and hydrogenated In2O3 (IO:H) films, improved the fill factor (FF) and short-circuit current density (Jsc) simultaneously. The best SHJ cell (243.4 cm2) containing ICO:H films had a conversion efficiency of 24.1%, open-circuit voltage of 745 mV, Jsc of 38.8 mA/cm2, and FF of 83.2% because of their high Hall mobility of 140 cm2/V s. We have clarified the following design principles for ICO:H films: (i) the Ce species substituted for In atoms acts as a donor and (ii) CeO2 and H decrease the residual strain and the contribution of the grain boundary scattering to carrier transport. This co-doping method can produce high conversion efficiencies in all solar cells containing TCO with resistive emitters.