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Suppressing Efficiency Roll-Off at High Current Densities for Ultra-Bright Green Perovskite Light-Emitting Diodes
摘要： Perovskite light-emitting diodes (PeLEDs) have undergone rapid development in the last several years with external quantum efficiencies (EQE) reaching over 21%. However, most PeLEDs still suffer from severe efficiency roll-off (droop) at high injection current densities, thus limiting their achievable brightness and presenting a challenge to their use in laser diode applications. In this work, we show that the roll-off characteristics of PeLEDs are affected by a combination of charge injection imbalance, nonradiative Auger recombination, and Joule heating. To realize ultrabright and efficient PeLEDs, several strategies have been applied. First, we designed an energy ladder to balance the electron and hole transport. Second, we optimized perovskite materials to possess reduced Auger recombination rates and improved carrier mobility. Third, we replaced glass substrates with sapphire substrates to better dissipate joule heat. Finally, by applying a current-focusing architecture, we achieved PeLEDs with a record luminance of 7.6 Mcd/m2. The devices can be operated at very high current densities (J) up to ~ 1 kA/cm2. Our work suggests a broad application prospect of perovskite materials for high-brightness LEDs and ultimately a potential for solution-processed electrically pumped laser diodes.
关键词： Joule heat,efficiency roll-off,Auger recombination,charge injection balance,high injection current density,ultrahigh brightness,perovskite light emitting diodes
更新于2025-09-23 15:19:57
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A “Positive Incentive” Approach to Enhance Operational Stability of Quantum Dot based Light-Emitting Diode
摘要： Balanced charge injection promises high efficiency of quantum dot based light-emitting diodes (QD-LEDs). Most widely used approach to realize charge injection balance is impeding the injection rate of the dominant charge carrier with energetic barriers. However, these approaches often accompany unwanted outcomes (e.g., the increase in operation voltage) that sacrifice the operation stability of devices. Herein, a “positive incentive” approach is proposed to enhance the efficiency and the operational stability of QD-LEDs. Specifically, the supply of hole, an inferior carrier than its counterpart, is facilitated by adopting a thin fullerene (C60) interlayer at the interface between hole injection layer (MoOX) and hole transport layer (CBP). The C60 interlayer boosts the hole current by eliminating the universal energy barrier, lowers the operation voltage of QD-LEDs, and enhances the charge balance in the QD emissive layer within working device. Consequently, QD-LEDs benefitting from the adoption of C60 interlayer exhibit significantly enhanced device efficiency and operation stability. Grounded on the quantitative assessment of the charge injection imbalance within the QD emissive layer, the impact of electrical parameters of QD-LEDs to their optoelectronic performance and operational stability is also discussed.
关键词： hole injection barrier,operational stability,fullerene,quantum dot based light-emitting diodes,charge injection balance
更新于2025-09-16 10:30:52