Improving the Performance of Perovskite Solar Cells with Sodium Stearate-Doped PEDOT:PSS as a Hole Transport Layer

Inverted perovskite solar cells (PSCs) have drawn growing research attention owing to their inherent merits of low-temperature manufacturing, reduced hysteresis effects, and promising industrial prospects. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a favorite hole transport material in inverted PSCs because of its solubility, excellent conductivity, and exceptional optical transparency. However, the mismatch of the energy level between PEDOT:PSS and perovskite limits the further improvement of device performance. Here, we proposed a simple method to reduce this energy level mismatch by doping the appropriate concentration of sodium stearate (NaSt) into PEDOT:PSS solution. Our results show that the power conversion efficiency (PCE) increases from 19.69% of the reference device employing pristine PEDOT:PSS as a hole transport layer (HTL) to 21.77% of the target device with 4 μg/mL NaSt-doped PEDOT:PSS HTL. The significant improvement of PCE mainly originates from the fine-tuning of the energy level of PEDOT:PSS by the NaSt dopant, which is helpful to align it more harmoniously with the perovskite layer and facilitates efficient charge transport. Thus, our study presents a simple and effective method to adjust the PEDOT:PSS HTL, which is beneficial for improving the photovoltaic performance of inverted PSCs.