High-efficiency all-polymer ternary blends enable exceptional thermal stability in organic photovoltaics

Abstract

Organic photovoltaics (OPVs) hold great promise due to their flexibility, lightweight nature, and compatibility with solution processing. However, achieving both high efficiency and thermal stability remains a significant challenge. In this study, the polymer donor PBQx-TF was blended with the high-crystallinity polymer D18, followed by the sequential deposition of the polymer acceptor PY-IT. Molecular packing differences between PBQx-TF and D18 films affected PY-IT layer deposition, impacting device charge transport. Ternary blending optimized morphology, balancing electron/hole mobility and reducing recombination. This, combined with optimized energy level alignment and minimized energy losses, enabled the ternary all-polymer OPV to achieve a power conversion efficiency (PCE) of 16.07%, surpassing the PCEs of the corresponding binary devices, which yielded 15.26% (PBQx-TF : PY-IT) and 14.39% (D18 : PY-IT), respectively. The optimized ternary OPV devices exhibited remarkable thermal stability, retaining 80% of their initial PCE following 1500 hours of sustained thermal stress at 120 °C, with structural integrity maintained across all device layers. This performance represents one of the highest levels of thermal stability reported for OPVs, underscoring the critical contribution of D18 as a third component in enhancing both the morphological stability and overall PCE. The ternary strategy-revealed correlation between thermal stability and morphology is crucial for the future development of high-performance and highly stable OPVs, potentially accelerating their commercialization.