Effectively balancing carrier injection of perovskite LEDs (PeLEDs) for next-generation display and illumination urgently needs for molecularly understanding carrier injection behavior of electron transport layer (ETL)/perovskite toward further developing high performance PeLEDs. Here, we molecularly reveal the electron injection behaviors of PeLEDs by theoretically-experimentally decoupling the electron transport of ETLs and electron injection of TmPyPB/perovskite and TPBi/perovskite. Resulted, the better molecular planarity bridging effect (MPBE) of TmPyPB than TPBi can effectively increase electronic-coupling for the improved electron transport ability and significantly decrease injection barrier for the enhanced electron injection capability, intrinsically leading to a more balanced carrier injection and a less electron accumulation of PeLEDs. Compared to TPBi-based PeLEDs, the TmPyPB-based PeLEDs present the obviously-increased average EQE, current efficiency, power efficiency and luminance by 44 %, 63 %, 43 % and 100 %, respectively. Meanwhile, this PeLED shows a higher voltage tolerance characteristic of 7.5 V than that of TPBi-based PeLEDs (6.25 V). Therefore, this work may provide a fundamental insight into carrier injection behavior of PeLEDs for effectively-regulating its carrier injection balance and further for its greatly-facilitated commercialization.
An efficient perovkite light-emitting diode (PeLED) is fabricated by incorporating 1,3,5-tri (m-pyrid-3-yl-phenyl)benzene (TmPyPB) between the emitting layer (EML) and the electron transporting layer (ETL), where TmPyPB plays an indispensable blocking effect on both excitons and holes. It shows a maximum current efficiency of 9.37 cd/A, and the corresponding external quantum efficiency (EQE) of 2.42% with a saturated green color Commission International de I'Eclairage (CIE1993) coordinated of (0.1279, 0.7951) under a driving voltage of 6 V. Meanwhile, the operational lifetime of the TmPyPB-based PeLED is improved to about 2.6-fold to that of the one with only the traditional ETL of aluminum 8-hydroxyquinolinate (Alq 3 ). The enhancements of electroluminescence (EL) performance are mainly attributed to better confinement of both the holes and the excitons in the EML, and more balanced carrier transportation in the TmPyPB-based PeLED. This work offers a feasible strategy to develop high performance optoelectronic devices.
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