Multifunctional guanidinium thiocyanate additive to enhance the performance of quasi-two-dimensional perovskite blue-emitting devices

Phase distribution, defect density, and charge transport of quasi-two-dimensional perovskites are the important factors determining the performance of the related light-emitting devices. Herein, the effects of the guanidinium thiocyanate (GaSCN) addition on the photo-physical, crystallographical, morphological, charge transport, and electroluminescent properties of the quasi-two-dimensional perovskites were studied. SCN adjusted the phase distribution by increasing the n = 2 phase content and decreasing the n = 3 and n = 4 phase contents, which facilitated the charge funneling. Ga+ mainly contributed to reducing the defect density. In addition, GaSCN increased the crystallinity, promoting the charge transport. Consequently, the quasi-two-dimensional perovskite blue-emitting device with GaSCN showed the maximum external quantum efficiency of 8.39%, which was 4.26 times that of the control device without GaSCN, together with the improved spectral and operational stabilities. This work highlights that the incorporation of a pseudohalide additive to simultaneously adjust the phase distribution, passivate defects, and promote the charge transport is promising for enhancing the performance of quasi-two-dimensional perovskite blue-emitting devices.