Solving the Contradiction of Work Function and Conductivity in PEDOT:PSS to Achieve High-Performance Perovskite Light-Emitting Diode via Aniline Interface Modification

Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is one of the most widely used functional materials for hole transport layer in perovskite light-emitting diode (LED). Tuning its work function (WF) and conductivity (κ) is a key issue for promoting perovskite LED performance. While decreasing its WF always reduces its κ and vice versa. Solving such contradiction is quite significant for promoting the development and commercialization of perovskite LED. Herein, the aniline (Ani) is employed for PEDOT:PSS interface modification. Ani inserted between PEDOT and PSS to weaken electrostatic interaction between sulfonic acid group in PSS chain and thiophene group in PEDOT chain, which results in increased delocalized electrons to enhance its κ. More importantly, the acid–base reaction decreases high acidity of PEDOT:PSS, which is an effective way to increase its WF and decrease its interface defects density. Meanwhile, such interface modification avoids PEDOT:PSS phase separation and ensures the uniformity of film. After Ani modification, the WF of PEDOT:PSS increase from 5.16 to 5.31 eV, the κ increases from 0.30 to 8.62 S cm⁻¹, and the hole mobility enhances from 0.716 × 10⁻⁶ to 1.306 × 10⁻⁶ cm² V⁻¹ s⁻¹. Modified PEDOT:PSS boost CsPbI₃ LED achieving a maximum external quantum efficiency of 17.70%.