Enhancing charge transport and device stability of MAPbI3 perovskite solar cells by hole-transport bilayer

Perovskite solar cells (PSCs) have attracted widespread attention and have gained rapid progress. The poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is widely used as a hole transport layer (HTL) in inverted architectures. However, the devices based on PEDOT:PSS suffer from low efficiency and poor stability, primarily due to energy-level misalignment and an unfavorable HTL/perovskite interface. Herein, a poly (triarylamine) (PTAA) layer is deposited on top of the PEDOT:PSS film to construct a PEDOT:PSS/PTAA hole-transport bilayer, thereby improving the interface between PEDOT:PSS and the perovskite and boosting the performance of PSCs. The introduction of the PTAA layer mitigates the hydrophilicity of PEDOT:PSS, realizes energy-band alignment, and accelerates carrier extraction. Consequently, the power-conversion efficiency (PCE) of the PSCs increased from 21.95% to 22.81%. Unencapsulated devices retain >70% of initial performance after 30 days at a humidity of ∼20% and room temperature, substantially outperforming the device with a PEDOT:PSS layer (∼40%). This work provides an easily accessible bilayer HTL strategy that boosts both efficiency and stability of PEDOT:PSS-based inverted PSCs. • PEDOT:PSS/PTAA hole transport-bilayer blocks moisture in perovskite films. • The optimized energy-level alignment facilitates hole extraction. • Hole-transport bilayer ensures high PCE and long-term device stability.