All-polymer solar cells (all-PSCs), while having the merits of material robustness, high mechanical flexibility, and low sensitivity of photovoltaic efficiencies to thickness variation, still suffer from non-satisfactory photovoltaic performance. This is largely due to the difficulty of morphology control at the polymeric donor–acceptor interface, subject to the strong intermolecular interaction and entanglement effects. Here, by in situ optical and structural analyses we unveiled the evolution of interface morphology in all-PSCs prepared with solution-based sequential deposition (SSD). We show that by incorporating a band-gap resembling small molecule BTA3 as an expander into the donor host, a favorable dissolution/swelling effect is achieved, which modifies the interpolation within the blends, the crystallization quality of the polymer donor and the infiltration of the acceptor, eventually leading to optimized pseudo-planar heterojunction morphology. We clarify that during morphology establishment, the BTA3 expander plays a vital role in boosting the long-range molecular ordering in the photoactive layer, which improves carrier transport and reduces recombination losses. The PM6+BTA3/PY-IT based all-PSCs yielded impressive photovoltaic efficiencies of 19.39% and 17.71% for small-area (0.04 cm²) and large-area (1 cm²) devices. Across a range of representative acceptor molecules as expanders, we established a universal correlation between the polymer host-small molecule expander interaction and device efficiency enhancements, which provides useful guidelines for achieving further efficiency boosts in polymer solar cells.

中文翻译：

---

溶出溶胀效应辅助界面形态细化可实现高效全聚合物太阳能电池


全聚合物太阳能电池 （all-PSCs） 虽然具有材料坚固性、高机械柔韧性和光伏效率对厚度变化的低敏感性等优点，但光伏性能仍然不令人满意。这主要是由于聚合物供体-受体界面的形态控制困难，受强分子间相互作用和纠缠效应的影响。在这里，通过原位光学和结构分析，我们揭示了用基于溶液的顺序沉积 （SSD） 制备的全 PSC 中界面形态的演变。我们表明，通过将类似于小分子 BTA3 的带隙作为膨胀剂掺入供体宿主中，实现了良好的溶解/溶胀效果，从而改变了共混物内的插值、聚合物供体的结晶质量和受体的浸润，最终导致优化的准平面异质结形态。我们阐明了在形态建立过程中，BTA3 扩增剂在促进光活性层中的长程分子有序方面起着至关重要的作用，从而改善了载流子运输并减少了复合损失。基于 PM6+BTA3/PY-IT 的全 PSC 为小面积 （0.04 cm²） 和大面积 （1 cm²） 器件产生了令人印象深刻的 19.39% 和 17.71% 的光伏效率。在一系列作为膨胀剂的代表性受体分子中，我们建立了聚合物宿主-小分子膨胀剂相互作用与器件效率提高之间的普遍相关性，这为进一步提高聚合物太阳能电池的效率提供了有用的指导。