Efficient and Stable Inverted Perovskite Solar Cell using Potassium Fluoroborate Doped PEDOT:PSS

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is widely used as a hole transport layer in inverted perovskite solar cells (PSCs) due to its simple fabrication process and high stability. However, there are severe interface defects between PEDOT:PSS and the perovskite layer, leading to poor power conversion efficiency (PCE) of the inverted devices. Herein, a hole transport layer (PEDOT:PSS) doped with potassium fluoroborate is introduced. The aqueous solution of KBF4 diluted with PEDOT:PSS is cleverly utilized to compare with PEDOT:PSS diluted with deionized aqueous solution. X-ray photoelectron spectroscopy of PEDOT:PSS confirms the reduction of PSS chains and an increase in conductivity after KBF4 doping. Moreover, KBF4 doping promotes crystal growth, resulting in larger grain size of the perovskite film. Additionally, the defects at the PEDOT:PSS/perovskite interface are effectively passivated, suppressing nonradiative recombination. The results show improved short-circuit current density, open-circuit voltage, and fill factor, resulting in a PCE of 19.76%, which is a 17.9% enhancement compared to the original device's 16.75%. The optimized device also exhibits long-term stability exceeding 1000 h, providing a simple and effective strategy for improving the PCE and stability of inverted PSCs.