Doping PEDOT:PSS with a cobalt complex boosts organic/silicon hybrid solar cell performance

Abstract

PEDOT:PSS/silicon hybrid solar cells have attracted much attention due to their simple fabrication process and low cost. However, the pristine PEDOT:PSS layer suffers from low electrical conductivity and a relatively low work function (WF), which severely limit the performance of the devices. To address this issue, we propose a facile and efficient p-doping strategy by incorporating a cobalt(III) complex, tris(2-(1H-pyrazol-1-yl)-4- tert -butylpyridine)-cobalt(III)tris(bis(trifluoromethylsulfonyl)imide) (FK209), into PEDOT:PSS. The Co(III) center can accept electrons from the PEDOT chains, triggering a redox reaction that increases the oxidation state of PEDOT, induces a coil‑to‑linear conformational transition, and promotes phase separation, thereby forming a PEDOT-rich conductive network. As a result, the electrical conductivity of PEDOT:PSS increases from 757.6 to 918.4 S/cm, and the WF rises from 4.82 to 4.92 eV upon optimal doping (2.3 mg/ml FK209). The corresponding PEDOT:PSS/silicon hybrid solar cell achieves an efficiency of 15.24%, with an open‑circuit voltage of 635.69 mV and a fill factor of 80.00%, significantly surpassing the pristine device (13.65%). This work provides a simple and highly promising route toward high-performance, low-cost organic/silicon hybrid solar cells.