Host–Guest Doping Strategy Enables Efficient Perovskite Light-Emitting Diodes with Suppressed Roll-Off

Improving exciton utilization and reducing nonradiative recombination are the most effective methods for achieving excellent performance in perovskite light-emitting diodes (PeLEDs). Although exciton utilization can be enhanced through surface defect passivation or energy transfer at interfaces, the role of energy transfer within the perovskite emissive layer has not been fully understood due to the complex nature of exciton recombination and decay dynamics. Here, we demonstrate a feasible host–guest doping strategy using 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), which has high triplet energy levels (T1), to enhance exciton utilization by effectively facilitating energy transfer in the perovskite emission layer. The N atoms of TPBi firmly bond to the perovskite through a coordination bond and effectively stabilize the perovskite structure. In addition to this, TPBi can also raise the electron mobility, increase the carrier complex probability, and expand the carrier complex region. As a result, the produced device of TPBi as host can achieve a maximum luminance (Lmax) of 61704 cd m–2 and a maximum external quantum efficiency (EQEmax) of 18.26%, as well as a 118.8% increase in the maximum EQE compared to the undoped device. The EQE can maintain a low-efficiency roll-off of 4.3% under 28,271 cd m–2. This study reveals that the host–guest doping strategy provides a way for improving the exciton management in PeLEDs.