Non-Halogenated Solvents and Layer-by-Layer Blade-Coated Ternary Organic Solar Cells via Cascade Acceptor Adjusting Morphology and Crystallization to Reduce Energy Loss
Youzhan Li, Jiang Wu, Hao Tang, Xueting Yi, Zekun Liu, Qingqing Yang, Yingying Fu, Jian Liu, Zhiyuan Xie
Abstract
The power conversion efficiency (PCE) of halogenated solvent spin-coated organic solar cells (OSCs) has been boosted to a high level (>18%) by developing efficient photovoltaic materials and precise morphological control. However, the PCE of OSCs prepared from non-halogenated solvents and with a scalable printing process is far behind, limited by tough morphology manipulation. Herein, we have fabricated ternary OSCs by using layer-by-layer (LBL) blade-coating and a non-halogenated solvent. The ternary OSCs based on the PM6:IT-M(1:0.2)/BTP-eC9 active layer are processed with the hydrocarbon solvent 1,2,4-trimethylbenzene with no need of any additives and post-treatment. The vertical donor/acceptor distribution is optimized by LBL blade-coating within the PM6:IT-M(1:0.2)/BTP-eC9 active layer. The cascade acceptor IT-M blended in PM6 not only attenuates the damage of BTP-eC9 to the PM6 crystallization, leading to a dense nanofiber-like morphology, but also prefers to reside between PM6 and BTP-eC9 to form a cascade energy level alignment for a fast charge-transfer process. Finally, the improved morphology and crystallization lead to a reduced molecular recombination, low energy loss, and high open-circuit voltage. The prepared non-halogenated solvent and LBL blade-coated OSCs achieve a PCE of 17.16%. The work provides an approach to fabricate hydrocarbon solvent-processed high-performance OSCs by employing LBL blade-coating and a ternary strategy.