High-quality WS2 film as a hole transport layer in high-efficiency non-fullerene organic solar cells

Liquid-exfoliated 2D transition metal disulfides (TMDs) are potential substitutes for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as hole transport layers (HTLs) in Organic Solar Cells (OSCs). Herein, high-yield and high-quality WS2 flake layers are prepared by comprehensively controlling the initial concentration, sonication processing time and centrifugal speed. The WS2 layers deposited on in situ transparent indium tin oxide (ITO) without plasma treatment show higher uniformity and conductivity than that formed on ITO after plasma treatment. With a significant increase in the short-circuit current density (JSC), the power conversion efficiency (PCE) of PM6:Y6-based non-fullerene OSCs using optimized WS2 as the HTL is higher than that using PEDOT:PSS as the HTL(15.75% vs. 15.31%). Combining the morphology characteristics with carrier recombination characteristics, the higher quality of the ITO/WS2 composite substrate leads to better charge transport and a lower bimolecular recombination rate in OSCs, thereby improving the device performance.