Near quantitative upconversion via triplet-triplet annihilation enabled by barrierless high-level reverse intersystem crossing

Photon upconversion is a non-linear optical process where two photons of low-energy are converted to one higher-energy photon. Between triplet-triplet annihilation (TTA) and lanthanide-doped systems, TTA-based systems can undergo upconversion at relatively low excitation intensities, while the lanthanide systems often require a laser source to provide enough of a driving force to upconvert, which limits their potential applicability. Here, we investigate the TTA process in 9,10-bis[(triisopropylsilyl)ethynyl]anthracene (TIPS-An) and 2-phenyl-9,10 bis[(triisopropylsilyl)ethynyl]anthracene (AnP) to compare twith diphenyanthracene (DPA), the typical emitter using for TTA-based upconversion. We show that TIPS-An can combine the energy in triplet excitons without significant losses because of high-level reverse intersystem crossing is barrierless