Hyperfluorescence shows great promise for the next generation of commercially feasible blue organic light-emitting diodes, for which eliminating the Dexter transfer to terminal emitter triplet states is key to efficiency and stability. Current devices rely on high-gap matrices to prevent Dexter transfer, which unfortunately leads to overly complex devices from a fabrication standpoint. Here we introduce a molecular design where ultranarrowband blue emitters are covalently encapsulated by insulating alkylene straps. Organic light-emitting diodes with simple emissive layers consisting of pristine thermally activated delayed fluorescence hosts doped with encapsulated terminal emitters exhibit negligible external quantum efficiency drops compared with non-doped devices, enabling a maximum external quantum efficiency of 21.5%. To explain the high efficiency in the absence of high-gap matrices, we turn to transient absorption spectroscopy. It is directly observed that Dexter transfer from a pristine thermally activated delayed fluorescence sensitizer host can be substantially reduced by an encapsulated terminal emitter, opening the door to highly efficient ‘matrix-free’ blue hyperfluorescence.

超荧光显示出下一代商业上可行的蓝色有机发光二极管的巨大前景，消除向终端发射极三重态的 Dexter 转移是效率和稳定性的关键。当前的器件依靠高间隙矩阵来防止 Dexter 转移，不幸的是，从制造的角度来看，这会导致器件过于复杂。在这里，我们介绍了一种分子设计，其中超窄带蓝色发射体被绝缘亚烷基带共价封装。具有简单发射层的有机发光二极管由掺杂有封装终端发射体的原始热激活延迟荧光主体组成，与非掺杂器件相比，外部量子效率下降可以忽略不计，最大外部量子效率可达 21.5%。为了解释在没有高间隙矩阵的情况下的高效率，我们转向瞬态吸收光谱。直接观察到，封装的终端发射器可以大大减少来自原始热激活延迟荧光敏化剂主体的 Dexter 转移，从而为高效“无基质”蓝色超荧光打开了大门。