Improved performance of pure red perovskite light-emitting devices based on CsPb(Br 1-x I x ) 3 with variable content of iodine and bromine.

All-inorganic cubic α - C s P b I ₃ perovskite for red perovskite light-emitting device (PeLED) applications is suffering from a phase transition. Unstable black α phase tends to transit to yellow δ phase under ambient conditions, which results in poor performance of the C s P b I ₃ -based PeLEDs. Partial replacement of iodine anion with a comparatively smaller bromine anion in the perovskite film can effectively adjust the Goldschmidt tolerance factor and stabilize the α -phase. A phase-stable C s P b ( B r _{1- x} I _x ) ₃ perovskite has been obtained at low annealing temperature of 50°C by tuning the iodine-to-bromine ratios. A PeLED with pure red emission based on the C s P b ( B r _0.43 I _0.57 ) ₃ perovskite has been demonstrated. The maximum luminance and efficiency were 2200 c d / m ² and 0.38 cd/A, respectively. Moreover, the PTAA layer was introduced between the PEDOT:PSS and perovskite film to improve the surface morphologies of perovskite. As a result, red PeLEDs with a maximum luminance of 2765 c d / m ² have been achieved.