Persistent luminescence is a fascinating phenomenon with exceptional applications. However, the development of organic materials capable of persistent luminescence, such as organic persistent room-temperature phosphorescence, lags behind for their normally low efficiency. Moreover, enhancing the phosphorescence efficiency of organic luminophores often results in short lifetime, which sets an irreconcilable obstacle. Here we report a strategy to boost the efficiency of phosphorescence by intramolecular triplet-triplet energy transfer. Incorpotation of (bromo)dibenzofuran or (bromo)dibenzothiophene to carbazole has boosted the intersystem crossing and provided an intramolecular triplet-state bridge to offer a near quantitative exothermic triplet–triplet energy transfer to repopulate the lowest triplet-state of carbazole. All these factors work together to contribute the efficient phosphorescence. The generation and transfer of triplet excitons within a single molecule is revealed by low-temperature spectra, energy level and lifetime investigations. The strategy developed here will enable the development of efficient phosphorescent materials for potential high-tech applications.

持续发光是一种引人入胜的现象，具有特殊的应用。然而，能够持久发光的有机材料（例如有机持久室温磷光）的开发由于其通常的低效率而滞后。而且，提高有机发光体的磷光效率通常导致寿命短，这设置了不可调节的障碍。在这里，我们报告了一种通过分子内三重态-三重态-三重态能量转移来提高磷光效率的策略。（溴）二苯并呋喃或（溴）二苯并噻吩向咔唑的配位增加了系统间的穿越，并提供了分子内三重态桥，从而提供了近定量的放热三重态-三重态能量转移，从而重新填充了咔唑的最低三重态。所有这些因素共同作用以促进有效的磷光。低温光谱，能级和寿命研究揭示了单个分子内三重态激子的产生和转移。此处制定的策略将使潜在的高科技应用能够开发出有效的磷光材料。