The hole transport layer with ammonia-modified to improve luminescence efficiency of all-inorganic perovskite light-emitting diodes

Recently, all-inorganic perovskite CsPbBr₃ has been shown to be promising for light-emitting diode applications because of its higher thermal stability and photoluminescence quantum efficiency. However, the performance of all-inorganic perovskite applied to PeLED devices still needs to be further improved. In this paper, a strategy to modify the PEDOT:PSS transport layer with ammonia was successfully developed, and an all-inorganic perovskite light-emitting diode with a ITO/PEDOT:PSS/CsPbBr₃/TPBi/LiF/Al structure was fabricated. It is shown that the ammonia-modified PEDOT:PSS not only improved the interfacial energy barrier between the PEDOT:PSS and CsPbBr₃ layer which effectively improved the charge injection balance rate and then decreased the turn-on voltage of the proposed devices from 2.6 V to 2.3 V. In addition, the maximum luminance of the devices was increased by 5 times (2540 Cd/m² to 14025Cd/m²), and both the current efficiency and external quantum efficiency (EQE) were enhanced 2.6 fold (1.61Cd/A to 4.17Cd/A and 0.45%–1.16% respectively). The mechanism was investigated and was found to be due to the enhancement of the peak ratio of the intensity (I(100)/I(110)) of the CsPbBr₃ layer, which effectively improved the band edge radiative recombination. The PEDOT:PSS transport layer with ammonia not only lowered the interfacial energy barrier but also improved the morphology and changed the crystallization of the CsPbBr₃ layer.