Homogenizing the sulfonic acid distribution of DMF-modified PEDOT:PSS films and perovskite solar cells

Abstract Inverted perovskite solar cells using pristine PEDOT:PSS as the hole-transporting layer (HTL) have been widely studied for its less hysteresis and low-temperature preparation technologies. However, this device suffers from an inferior open-circuit voltage ( V OC ) and stability problems. Several attempts have made on film formation and interface engineering to improve the efficiency. Modification proved beneficial to decrease energy offset at the interface between the HTL layer and the adjacent perovskite layer. In this paper, modification PEDOT:PSS layers were realized with a dimethyl formamide (DMF) solvent. The sulfonic acid distribution was homogenized in the normal direction after modification. The work function of the modified PEDOT:PSS layers increased from 4.71 to 5.07 eV, and the conductivity of modified PEDOT:PSS increased from 3 × 10 −4 to 0.45 S/cm. The as-deposited perovskite films were more uniform with larger grain sizes and less pinholes, resulting in an improved V OC from 0.93 to 1.048 V, while the efficiency was increased from 11.5% to 16.8%. Solar cells without encapsulation under the 50 h and 50% humidity aging test showed 7% degradation of fill factor (FF) with 50 v/v% PEDOT:PSS layer, while the fill factor decreased 11.2% in the 0 v/v% PEDOT:PSS layer, respectively.