Prashanthan, K.; Levine, I.; Musiienko, A.; Gutierrez-Partida, E.; Hempel, H.; Lips, K.; Unold, T.; Stolterfoht, M.; Dittrich, T.; MacQueen, R.W.: Internal electric fields control triplet formation in halide perovskite-sensitized photon upconverters. iScience 26 (2023), p. 106365/1-20
10.1016/J.isci.2023.106365
Open Access Version
Abstract:
Halide perovskite-based photon upconverters utilize perovskite thin films to sensitize triplet exciton formation in a small-molecule layer, driving triplet- triplet annihilation upconversion. Despite having excellent carrier mobility, these systems suffer from inefficient triplet formation at the perovskite/annihi- lator interface. We studied triplet formation in formamidinium-methylammo- nium lead iodide/rubrene bilayers using photoluminescence and surface photovoltage methods. By studying systems constructed on glass as well as hole-selective substrates, comprising self-assembled layers of the carbazole de- rivative 2PACz ([2-(9H-carbazol-9-yl)ethyl]phosphonic acid) on indium-doped tin oxide, we saw how changes in the carrier dynamics induced by the hole-selec- tive substrate perturbed triplet formation at the perovskite/rubrene interface. We propose that an internal electric field, caused by hole transfer at the perov- skite/rubrene interface, strongly affects triplet exciton formation, accelerating exciton-forming electron-hole encounters at the interface but also limiting the hole density in rubrene at high excitation densities. Controlling this field is a promising path to improving triplet formation in perovskite/annihilator upconverters.