Electrodeposited transparent PEDOT for inverted perovskite solar cells: improved charge transport and catalytic performances

The acidic, corrosive effect of sodium polystyrene sulfonate (PSS) in poly 3,4-ethylenedioxythiophene:sodium polystyrene sulfonate (PEDOT:PSS) limits the stability of inverted perovskite solar cells (PSCs) based on the ITO/PEDOT:PSS/perovskite/PCBM/BCP/Ag structure. In this work, a poly 3,4-ethylenedioxythiophene (PEDOT) hole transport layer (HTL) with high hole mobility and good catalytic performance was prepared by electrochemical cyclic voltammetry (CV) method for inverted PSCs. By controlling the CV cycles (from 1 to 5 cycles) and EDOT monomer solution concentration (from 0.5 to 2.0 mmol·L−1) of electrochemical deposition, the thickness, morphology, optical and electrochemical properties of PEDOT could be accurately adjusted. The optimal photovoltaic performance with current density (Jsc) of 22.19 mA·cm−2, open circuit voltage (Voc) of 0.94 V, fill factor (FF) of 0.65 and photoelectric conversion efficiency of 13.56% was obtained when deposition of PEDOT with 1 CV cycle and EDOT concentration of 0.5 mmol·L−1. At this point, the perovskite showed good crystallization, optimal optical, charge transport and recombination performance, resulting in better Voc and photoelectric conversion efficiency (PCE) compared to the devices with higher CV cycle numbers and 3,4-ethylenedioxythiophene (EDOT) concentration. For comparison with spin-coated PEDOT:PSS, the device with electrodeposited PEDOT showed improved Jsc and comparable Voc, which may result from its better charge transport and catalytic ability. The device with spin-coated PEDOT:PSS showed photoelectric conversion efficiency of 12.25%, which was lower than that based on electrodeposited PEDOT (13.56%) with 1 CV cycles and 0.5 mmol·L−1 EDOT concentration. And the device with electrodeposited PEDOT as HTLs showed more excellent air stability. In ambient air ((32 ± 5) °C and RH: 70% ± 20%), it still maintained more than 80% of the initial photoelectric conversion efficiency after 1000 h. In comparison, the photoelectric conversion efficiency of the device with PEDOT:PSS decreased to 20% of the initial value after storage for 500 h. From this study, a facial and low-cost way to prepare PEDOT HTL with high performances that better than the traditional PEDOT:PSS has been explored, which is expected to eliminate the acidic, corrosive effect of PSS in PEDOT:PSS.