TY  - GEN
A1  - Wollscheid, Nikolaus
CY  - Heidelberg
TI  - The Ultrafast Singlet Fission Dynamics in Solution and Thin Film
N2  - Singlet fission (SF) is a process where two triplet charge-carriers are generated from one photoexcited singlet state. This opens up the possibility to increase the efficiency limit for single-junction solar cells by one third from 33% to 44%. In this work, the long-lasting question of the effect of competing pathways on the efficiency of SF is addressed by time-resolved spectroscopy and a novel global fit approach. This is demonstrated on two examples. First, SF is established in a new class of molecules, the tetraazaperopyrenes. Here, substituent-dependent factors, namely excimer formation as well as vibronic and spin-orbit coupling, are identified to be decisive for SF efficiency. Subsequently, solutions of (hetero-) acenes are investigated, in which comparisons between ambient conditions and deaerated solutions highlight the importance of molecular oxygen for SF: A new, sequential mechanism including atmospheric oxygen as a catalyst is resolved, which allows for a step-wise doubling of triplet states even at low chromophore concentrations. In concentrated solutions, diffusion-controlled SF outcompetes other reaction pathways resulting in triplet yields close to 200%. The absence of any intermediate species emphasises the efficiency of this process.
AV  - public
ID  - heidok29431
Y1  - 2021///
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/29431/
ER  -