Effect of mixed spacer cation on the performance of quasi-2D blue perovskite light-emitting diodes

Inorganic–organic hybrid perovskites have received extensive attention in the field of optoelectronic devices, due to its lower cost, high carrier mobility, high defect tolerance, narrow emission bandwidth and tunable emission spectra. In recent years, we have observed a rapid development of perovskite based light emitting diodes (LED), however, the performance of blue perovskite LED falls far behind the green and red LEDs. The blue perovskite LED suffers from the fast crystallization of chlorine based perovskite, and the instability of the mixture phase of chlorine and bromine under electrical stress. In this work, in order to improve the stability of blue LED, the macro-molecular material butylammonium chlorine (BACl) is introduced into three-dimensional cesium lead bromide (CsPbBr3) to form quasi two-dimensional perovskite structure. By adjusting the molar ratio of BACl over CsPbBr3, the number of inorganic layers (n) in the quasi-two-dimensional structure is finely tuned. A color stable perovskite light emitting diodes with wavelength ranging from 450-490nm (deep blue to sky blue) is achieved. Furthermore, phenethylammonium (PEA) cation, a water and oxygen stable aromatic material, is added into the quasi 2D perovskite precursor to form mixed spacer cation perovskite layer. The performance and stability of the blue LED with different molar proportion of BA+ to PEA+ is investigated. Finally, a color stable perovskite blue LED with luminance exceeding 1000 Cd/m2 is achieved.