Green Additive Limits Runaway Crystallinity in PM6:Y6 Organic Solar Cells but Causes Field-Independent Geminate Recombination
Green Additive Limits Runaway Crystallinity in PM6:Y6 Organic Solar Cells but Causes Field-Independent Geminate Recombination
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DOI：
10.1021/acsenergylett.3c01604
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发表时间：
2023-10
影响因子：
22
通讯作者：
O. Alqahtani;Awwad Alotaibi;Michael Burnes;Brian A. Collins
中科院分区：
文献类型：
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作者：
O. Alqahtani;Awwad Alotaibi;Michael Burnes;Brian A. Collins
溶剂添加剂已被广泛认可，可通过增强纳米域相分离和结晶来提高有机太阳能电池的器件性能。然而，最佳添加剂浓度通常为痕量，并有轻微波动，导致结晶度失控，从而缩短设备并限制放大潜力。在这里，我们展示了非卤化溶剂添加剂 1-苯基萘 (PN) 可用于优化高性能 PM6:Y6 设备，但即使浓度比最佳值高 10 倍，也不会出现结晶失控的情况。我们对器件损耗的整体分析表明，PN 增加了光吸收，同时减少了双分子重组。然而，在最佳值之上，由于电荷转移状态的场无关的成对重组，电荷产生减少，这克服了其他好处。旋转的 Y6 微晶取向可能是罪魁祸首，其中器件电场无法有效分离电荷。尽管如此，器件性能仍然高于传统添加剂，这表明了避免性能对加工条件高度敏感的途径。
Solvent additives are well-established for improving device performance of organic solar cells by enhancing nanodomain phase separation and crystallization. However, optimum additive concentrations are typically at trace amounts with slight fluctuations causing runaway crystallinity that short the device and limit scale-up potential. Here we show that a nonhalogenated solvent additive 1-phenylnaphthalene (PN) can be used to optimize high-performance PM6:Y6 devices, but without runaway crystallinity even at concentrations 10× above the optimum. Our holistic analysis of device losses shows that PN increases photoabsorption while decreasing bimolecular recombination. However, above the optimum, charge generation is reduced due to field-independent geminate recombination of charge transfer states that overcomes the other benefits. Rotated Y6 crystallite orientation is a likely culprit, where the device electric field is ineffective at separating the charges. Despite this, device performance remains higher than that of traditional additives, indicating a route to avoiding the high sensitivity of performance to processing conditions.