Improved Molecular Ordering in a Ternary Blend Enables All-Polymer Solar Cells over 18% Efficiency.

Although all-polymer solar cells (all-PSCs) show great commercialization prospects, their power conversion efficiencies (PCEs) still fall behind their small molecule acceptor-based counterparts. In all-polymer blends, the optimized morphology and high molecular ordering are difficult to achieve since there is trouble-some competition between the crystallinity of the polymer donor and acceptor during the film-formation process. Therefore, it is challenging to improve the photovoltaic performance of all-PSCs. We herein adopt a ternary strategy to modulate the morphology and the molecular crystallinity of an all-polymer blend, in which PM6:PY-82 was selected as the host blend and PY-DT was employed as a guest component. Benefiting from the favorable miscibility of the two acceptors and the higher regularity of PY-DT, the ternary matrix features a well-defined fibrillar morphology and improved molecular ordering. As a result, the champion PM6:PY-82:PY-DT device produces a record-high PCE of 18.03%, with simultaneously improved open-circuit voltage, short-circuit current and fill factor in comparison with the binary devices. High-performance large-area (1 cm 2 ) and thick-film (300 nm) all-PSCs were also successfully fabricated with PCEs of 16.35% and 15.70%, respectively. More importantly, 16.5 cm 2 organic solar module affords an encouraging PCE of 13.84% when using the non-halogenated solvent (o-xylene), showing the great potential of "Lab-to-Fab" transition of all-PSCs. This article is protected by copyright. All rights reserved.