Efficient and Photostable Organic Solar Cells Achieved by Alloyed Dimer Acceptors with Tailored Linker Structures

Abstract

High power conversion efficiency (PCE) and long-term stability are prerequisites for commercialization of organic solar cells (OSCs). Herein, two dimer acceptors (DYTVT and DYTCVT) are developed with different properties through linker engineering, and study their effects as alloy-like acceptors on the photovoltaic performance and photostability of OSCs. These ternary OSCs effectively combine the advantages of both dimer acceptors. DYTVT, characterized by its high backbone planarity, ensures elevated electron mobility and high glass-transition temperature (T-g), leading to efficient charge transport and enhanced photostability of OSCs. Conversely, DYTCVT, with its significant dipole moment and electrostatic potential, enhances compatibility of the alloy acceptors with donors and refines the blend morphology, facilitating efficient charge generation in OSCs. Consequently, D18:DYTVT:DYTCVT OSCs exhibit higher PCE (18.4%) compared to D18:MYT (monomer acceptor, PCE = 16.5%), D18:DYTVT (PCE = 17.4%), and D18:DYTCVT (PCE = 17.0%) OSCs. Furthermore, owing to higher T-g of alloy acceptors (133 degrees C) than MYT (T-g = 80 degrees C) and DYTCVT (T-g = 120 degrees C), D18:DYTVT:DYTCVT OSCs have significantly higher photostability (t(80%) lifetime = 4250 h under 1-sun illumination) compared to D18:MYT (t(80%) lifetime = 40 h) and D18:DYTCVT OSCs (t(80%) lifetime = 2910 h).