Nature Communications, Published online: 20 August 2026; doi:10.1038/s41467-026-76914-5 Efficiency roll-off in OLEDs is a challenge with multi-resonance thermally activated delayed fluorescence (MR-TADF) materials. Here, the authors add heavy-atom germanium into exciplex hosts to improve reverse intersystem crossing rates in diverse MR-TADF emitters without electronic structure changes.