Abstract

The use of singlet fission to enhance device efficiency or enable new capabilities raises the need to investigate it on a slow operational timescale. Using a transistor-based measurement to examine temperature-dependent singlet fission in tetracene single crystals, we observe that it is activated to 210 K, at which point it undergoes an optoelectronic phase transition. We compare these results to those of pentacene and suggest that the phase change is due to a change in the singlet fission kinetics. We further examine the interplay between this readout and other extrinsic and intrinsic device properties, such as disorder and trap states. Our results give insight not only into the readout mechanism of this OFET-based measurement, but also strategies to manipulate and tune the response.