Sodium Benzenesulfonate Modified Poly (3,4‐Ethylenedioxythiophene):Polystyrene Sulfonate with Improved Wettability and Work Function for Efficient and Stable Perovskite Solar Cells

The p‐type conducting polymer poly (3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is widely utilized as the hole transport layer (HTL) for solution‐processed planar perovskite solar cells (PSCs) with a p‐i‐n structure. However, the inverted PSCs based on PEDOT:PSS HTL suffer from deficient open‐circuit voltage (VOC) and poor stability issues, because of the high electron affinity and acid nature of PEDOT:PSS. Herein, sodium benzenesulfonate (C6H5SO3Na) (SBS) is applied to modify the PEDOT:PSS (SBS–PEDOT:PSS) layer to form a smoother surface and better energy‐level alignment with the perovskite layer. In addition, the SBS–PEDOT:PSS layer with improved hole extraction capacity and suppressed charge recombination, significantly increases the grain size and crystallinity of the MA0.8FA0.2PbI3‐xClx perovskite film. Consequently, the power conversion efficiency (PCE) and VOC of the inverted PSCs are improved from 18.07% and 1.04 V to 19.41% and 1.08 V, respectively, after SBS modification. Moreover, the efficiency of the unencapsulated PSCs based on SBS–PEDOT:PSS remains above 90% after storing in ambient condition for 20 days. This research provides an accessible route to surmount the intrinsic imperfection of PEDOT:PSS and ameliorate the performance of PSCs.