Simultaneously improving the efficiencies of organic photovoltaic devices and modules by finely manipulating the aggregation behaviors of Y-series molecules

The introduction of an electron deficient core (e.g.: BTP, dithiophene [3.2b] pyrrolobenzothiazole) was considered to be an effective strategy for modulating the electron-vibration coupling, delocalization, and molecular stacking of high-performance Y-series non-fullerene acceptors (NFAs). However, the above means often make it difficult to achieve precise control of the various aggregation behaviors of Y-series NFAs, which is a key factor of limiting the performance improvement in the final device. In this study, we present a novel liquid additive, an electronegative alkane, which strengthens non-covalent interactions and boosts electron coupling. This promotes rapid nucleation and crystallization of the Y-series molecule, enhancing molecular stacking and aggregation. Besides, the directional induction of the BTP core in the blend active layer is well maintained, which optimizes the charge transport and reduces trap-assisted recombination of the bulk heterojunction. As a result, our strategy has substantially improved the performance of multiple Y-series NFA OPV systems, enabling thick film (≥200 nm) large-area modules (19.31 cm²) with efficiencies exceeding 14%. We believe that the broader processing window offered by the thick film is a notable advancement towards the commercialization of organic photovoltaics.