Pensack Ryan D, Purdum Geoffrey E, Mazza Samuel M, Grieco Christopher, Asbury John B, Anthony John E, Loo Yueh-Lin, Scholes Gregory D
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
J Phys Chem C Nanomater Interfaces. 2022 Jun 16;126(23):9784-9793. doi: 10.1021/acs.jpcc.2c00897. Epub 2022 Jun 6.
Singlet fission is a process in conjugated organic materials that has the potential to considerably improve the performance of devices in many applications, including solar energy conversion. In any application involving singlet fission, efficient triplet harvesting is essential. At present, not much is known about molecular packing arrangements detrimental to singlet fission. In this work, we report a molecular packing arrangement in crystalline films of 5,14-bis(triisopropylsilylethynyl)-substituted pentacene, specifically a local (pairwise) packing arrangement, responsible for complete quenching of triplet pairs generated via singlet fission. We first demonstrate that the energetic condition necessary for singlet fission is satisfied in amorphous films of the 5,14-substituted pentacene derivative. However, while triplet pairs form highly efficiently in the amorphous films, only a modest yield of independent triplets is observed. In crystalline films, triplet pairs also form highly efficiently, although independent triplets are not observed because triplet pairs decay rapidly and are quenched completely. We assign the quenching to a rapid nonadiabatic transition directly to the ground state. Detrimental quenching is observed in crystalline films of two additional 5,14-bis(trialkylsilylethynyl)-substituted pentacenes with either ethyl or isobutyl substituents. Developing a better understanding of the losses identified in this work, and associated molecular packing, may benefit overcoming losses in solids of other singlet fission materials.
单线态裂变是共轭有机材料中的一种过程，它有可能显著提高包括太阳能转换在内的许多应用中器件的性能。在任何涉及单线态裂变的应用中，高效的三线态俘获都是至关重要的。目前，对于不利于单线态裂变的分子堆积排列了解不多。在这项工作中，我们报道了5,14 - 双（三异丙基甲硅烷基乙炔基）取代并五苯晶体薄膜中的一种分子堆积排列，具体来说是一种局部（成对）堆积排列，它导致通过单线态裂变产生的三线态对完全猝灭。我们首先证明，在5,14 - 取代并五苯衍生物的非晶薄膜中满足单线态裂变所需的能量条件。然而，虽然三线态对在非晶薄膜中高效形成，但仅观察到适度产率的独立三线态。在晶体薄膜中，三线态对也高效形成，尽管未观察到独立三线态，因为三线态对迅速衰减并完全猝灭。我们将这种猝灭归因于直接快速非绝热跃迁到基态。在另外两种带有乙基或异丁基取代基的5,14 - 双（三烷基甲硅烷基乙炔基）取代并五苯的晶体薄膜中也观察到了有害的猝灭。更好地理解这项工作中确定的损失以及相关的分子堆积，可能有助于克服其他单线态裂变材料固体中的损失。
