Slow Singlet Fission Observed in a Polycrystalline Perylenediimide Thin Film

Abstract

Singlet exciton fission (SF) is a process wherein an exciton in an organic semiconductor divides its energy to form two excitations. This process can offset thermalization losses in light harvesting technologies, but requires photostable materials with high SF efficiency. We report ultrafast kinetics of polycrystalline films of N-N'-dioctyl-3,4,9,10-perylenedicarboximide (C8-PDI), a chromophore predicted to undergo SF on picosecond time scales. While transient absorption measurements display picosecond dynamics, such kinetics are absent from low-fluence time-resolved emission experiments, indicating they result from singlet-singlet exciton annihilation. A model that accounts for annihilation can reproduce both measurements and highlights that care must be taken when extracting SF rates from time-resolved data. Our model also reveals SF proceeds in C8-PDI over 3.8 ns. Despite this slow rate, SF occurs in high yield (51%) due to a lack of competing singlet deactivation pathways. Our results show perylenediimides are a promising class of SF materials that merit further study.

Triplet Transfer Mediates Triplet Pair Separation during Singlet Fission in 6,13‐Bis(triisopropylsilylethynyl)‐Pentacene

“…Therefore, the ratio of second‐order decay constants provides a direct measure of the relative diffusion constants for triplet transfer within the SA and TA films. [11a,13]…”

Harnessing singlet exciton fission to break the Shockley–Queisser limit

“…However, the surge in interest in SF over the past 5 years has led to a dramatic increase in the number of chromophores known to undergo SF, with newly synthesised materials being added to the list all the time. It has been suggested that several polyacenes/polyacene dimers 11,[51][52][53] , PDIs 32,54,55 , terrylenes/TDIs 27,56 and CT-polymers 57 undergo efficient fission. Some of these molecules fulfil many of the above criteria, but none can fulfil all of them.…”

Optimization of energy transfer in a polymer composite with perylene chromophores

“…Singlet fission is a possible contributor to the reduction. [22][23][24][25] Since the emitter concentration must be much lower than the sensitizer concentration to produce a low self-absorption device, emitter self-aggregation effects are less important to solar concentrator design.…”