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

Abstract

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 (J_SC), 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.