Morphology‐Independent Efficient Singlet Exciton Fission in Perylene Diimide Thin Films

Perylene diimides are conjugated chromophores that are of considerable interest owing to their ability to transform a singlet excited state into two triplets by singlet fission. Although singlet fission has previously been reported for certain perylene diimide derivatives, there is some uncertainty about the rates and yield of the process in these materials. In this report, ultrafast transient absorption spectroscopy is used to demonstrate that singlet fission in perylene diimides can occur on a sub‐picosecond timescale with quantum yields approaching the theoretical limit of 200 %. Mind your morphology: Ultrafast transient absorption spectroscopic measurements were performed on crystalline and amorphous perylene diimide thin films and revealed the occurrence of singlet exciton fission on a sub‐picosecond timescale. By using a ground state bleach analysis, a maximum singlet fission efficiency of 200 % could be determined, which is unaffected by the film morphology (see figure).