High Built-in Potential Perovskite Solar Cells Realized by Incorporating a Hybrid Hole Extraction Layer

The performance of perovskite solar cells (PSCs) has been improved substantially over the past few years. However, the related fundamental understanding of improving the built-in potential on the efficiency of the PSCs is still far from adequate. A combination of morphology, charge extraction, and built-in potential studies would help us to gain an insight on efficient operation of the PSCs. Herein, the effect of the hybrid hole extraction layer (HEL), comprising a mixture of tungsten oxide (WO₃) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) (WO₃–PEDOT:PSS), on the growth of the perovskite photoactive layer and built-in potential in PSCs is investigated using structural analyses, photoelectron spectroscopy, and transient photocurrent (TPC) measurements. It shows that the use of hybrid HEL is an effective approach for enhancing the built-in potential across the photoactive layer in the PSCs, leading to >20% increase in power conversion efficiency as compared to that of a control PSC prepared using a pristine PEDOT:PSS HEL. PSCs with a higher built-in potential are favorable for efficient cell operation, as manifested by the charge extraction analyses and TPC measurements.