Singlet Fission in Thin Solid Films of Bis(thienyl)diketopyrrolopyrroles
David Rais, Petr Toman, Jiřı́ Pfleger, Udit Acharya, Yadu Ram Panthi, Miroslav Menšı́k, Alexander Zhigunov, Muhammed Arshad Thottappali, Martin Vala, Aneta Marková, Stanislav Stříteský, Martin Weiter, Martin Cigánek, Jozef Krajčovič, Karel Pauk, Aleš Imramovský, Alexandr Zaykov, Josef Michl
Abstract
Abstract The singlet fission (SF) process discovered in bis(thienyl)diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n ‐hexyl, n ‐butyl, or 2‐(adamant‐1‐yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, k SF , (7±4), (9±3) and (5.6±1.9) ns −1 for thin films of the three compounds, respectively, are roughly equal, but the triplet quantum yields vary strongly: (120±40), (160±40) and (70±16), respectively. The recent molecular pair model reproduces the near equality of all three k SF at the crystal geometries and identifies all possible pair arrangements in which SF is predicted to be faster, by up to two orders of magnitude. However, it is also clear that the presently non‐existent ability to predict the rates of processes competing with SF is pivotal for providing a guide for efforts to optimize the materials for PV.