Dynamic Color-Tunable Dual Room Temperature Phosphorescence via Activation of Both Host and Guest Triplet States

The design of dual organic room-temperature phosphorescence (RTP) from both the host and guest remains a significant challenge, as most organic doping systems generally enable either the guest or the host to serve as a single static phosphorescent emitter. Here we report a host-guest dual RTP system featuring dynamically tunable colors, controllable host-to-guest phosphorescence ratios, and widely tunable lifetimes of 18.8-472 ms. This unique performance is enabled by bidirectional triplet energy transfer processes between host and guest, which not only activates RTP of the host molecules but also induces a blue shift of the phosphorescence from 673 to 528 nm, with CIE chromaticity coordinates ranging from (0.51, 0.45) to (0.40, 0.57). More importantly, alkyl ring groups effectively modulate the triplet energy levels of the identical π-conjugated host molecules at the aggregate level, resulting in the lowest triplet energy levels of host crystals ranging from 2.88 to 2.53 eV. This work provides a unique insight into achieving dual RTP in organic doping systems and holds great potential for applications in multilevel information encryption and optoelectronics research.