Hole-extraction layer dependence of defect formation and operation of planar CH3NH3PbI3 perovskite solar cells

Abstract

Three planar CH3NH3PbI3 (MAPbI(3)) solar cells having the same structure except a hole-extraction layer (HEL) showed distinctive difference in operation characteristics. Analysis of frequency-dependent capacitance and dielectric-loss spectra of the three MAPbI(3) devices showed two types of recombination-loss channels with different time constants that we attributed respectively to interface and bulk defects. Discrepancy in defect formation among the three devices with a HEL of PEDOT: PSS, NiOx, or Cu-doped NiOx was not surprising because grain-size distribution and crystalline quality of MAPbI(3) can be affected by surface energy and morphology of underlying HELs. We were able to quantify interface and bulk defects in these MAPbI(3) solar cells based on systematic and simultaneous simulations of capacitance and dielectricloss spectra, and current-voltage characteristics by using the device simulator SCAPS. [GRAPHICS] . Defect density reduction is essential for efficient planar solar cells. Defect density in MAPbI(3) layers, with respect to which an open-cell voltage and a fill factor vary, can be investigated by using capacitance-frequency spectra.