Shenzhen Key Laboratory of Flexible Memory Materials and Devices, College of Electronic Science and Technology, Shenzhen University, Shenzhen 518000, China.
Nanoscale. 2019 Mar 14;11(11):5021-5029. doi: 10.1039/c8nr09864f.
Although all-inorganic perovskite light emitting diodes (PeLED) have satisfactory stability under an ambient atmosphere, producing devices with high performance is challenging. A device architecture with a reduced energy barrier between adjacent layers and optimized energy level alignment in the PeLED is critical to achieve high electroluminescence efficiency. In this study, we report the optimization of a CsPbBr3-based PeLED device structure with Li-doped TiO2 nanoparticles as the electron transport layer (ETL). Optimal Li doping balances charge carrier injection between the hole transport layer (HTL) and ETL, leading to superior performance in both devices. The turn-on voltages for devices with Li-doped TiO2 nanoparticles were significantly reduced from 7.7 V to 4.9 V and from 3 V to 2 V in the direct and inverted PeLED structures, respectively. The low turn-on voltage for green emission is one of the lowest values among the reported CsPbBr3-based PeLEDs. Further investigations show that the device with an inverted structure is superior to the device with a direct structure because the energy barrier for carrier injection was minimized. The inverted structure devices exhibited a current efficiency of 5.6 cd A-1 for the pristine TiO2 ETL, while it was 15.2 cd A-1 for the Li-doped TiO2 ETL, a factor of ∼2.7 enhancement at 5000 cd m-2.
虽然全无机钙钛矿发光二极管（PeLED）在环境气氛下具有令人满意的稳定性，但要制造出高性能的器件仍具有挑战性。在 PeLED 中，具有较小相邻层间能量势垒和优化的能级对准的器件结构对于实现高电致发光效率至关重要。在本研究中，我们报告了一种基于 CsPbBr3 的 PeLED 器件结构的优化，该结构采用 Li 掺杂 TiO2 纳米粒子作为电子传输层（ETL）。最佳的 Li 掺杂平衡了空穴传输层（HTL）和 ETL 之间的电荷载流子注入，从而使两种器件的性能都得到了改善。具有 Li 掺杂 TiO2 纳米粒子的器件的开启电压分别从 7.7 V 显著降低至 4.9 V 和从 3 V 降低至 2 V，无论是在直接 PeLED 结构还是在倒置 PeLED 结构中均如此。绿光发射的低开启电压是已报道的基于 CsPbBr3 的 PeLED 中最低值之一。进一步的研究表明，具有倒置结构的器件优于具有直接结构的器件，因为载流子注入的能量势垒最小化。倒置结构器件的原始 TiO2 ETL 的电流效率为 5.6 cd A-1，而 Li 掺杂 TiO2 ETL 的电流效率为 15.2 cd A-1，在 5000 cd m-2 时提高了约 2.7 倍。
