Abstract
We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21-Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core with triphenylene wings that protect the formal pentacene from chemical degradation. The electronic energy levels position singlet exciton fission to be endothermic, similar to tetracene despite the triphenylenes. TTBP exhibits rapid early time singlet fission with quantitative yield of triplet pairs within 100 ps followed by thermally activated separation to free triplet excitons over 65 ns. TTBP exhibits high photoluminescence quantum efficiency, close to 100% when dilute and 20% for solid films, arising from triplet-triplet annihilation. In using such a system for exciton multiplication in a solar cell, maximum thermodynamic performance requires radiative decay of the triplet population, observed here as emission from the singlet formed by recombination of triplet pairs. Combining chemical stabilisation with efficient endothermic fission provides a promising avenue towards singlet fission materials for use in photovoltaics.
Highlights
We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21-Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core with triphenylene wings that protect the formal pentacene from chemical degradation
As in a typical single-junction photovoltaic, a high photoluminescence efficiency is key to reducing voltage losses due to non-radiative decay in a potential singlet fission solar cell
The strong majority of TTBP is aggregated at 5% concentration in PS, with a minority of dispersed molecules, meaning that the transient absorption (TA) experiments for which the polystyrene blends were designed are dominated by the signal from aggregated TTBP
Summary
We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21-Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core with triphenylene wings that protect the formal pentacene from chemical degradation. Thanks to the favourable energetics that make singlet fission reversible, and notably slow non-radiative decay, TTBP has a high photoluminescence quantum efficiency (PLQE) of 20%, despite singlet fission to the pair state proceeding at ~200 times the radiative rate.
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