Optimization of SnO2-based electron-selective contacts for Si/PEDOT:PSS heterojunction solar cells

Tin oxide (SnO2) is a potentially excellent electron-selective contact (ESC) for silicon (Si)-based solar cells due to its satisfactory energy band structure and good crystallinity. However, unsatisfactory electron extraction ability and limited surface passivating effect of SnO2 ESCs will limit the performance of corresponding solar cells. We increase the Fermi level of SnO2 by doping Ethylene diamine tetraacetic acid (EDTA), which endows EDTA-SnO2 better electron extraction ability than SnO2. Moreover, EDTA-SnO2/SiOx bilayer ESC prepared by combining a EDTA-SnO2 layer and a thin silicon oxide (SiOx) film provides better surface passivation than EDTA-SnO2 ESC without impairing the charge transport capability markedly. The planar Si/PEDOT:PSS heterojunction solar cells (HSCs) with EDTA-SnO2/SiOx bilayer ESCs exhibit a power conversion efficiency (eta) of 11.52%, which improves 13.7% in comparison with the eta (10.13%) of HSCs with SnO2 ESCs, mainly caused by the increase in V-oc and FF by 18 mV and 5.4% respectively.