Control of perovskites crystallization via polymer scaffold towards pure blue Light-emitting diodes with high color purity

Efficient blue perovskite light-emitting diodes with stable and narrow wavelength have been realized by polymer modulated quasi-two dimensional EA 2 Cs n-1 Pb n Br 3n+1 perovskite films. The introduction of polyvinylpyrrolidone (PVP) can inhibit the growth of the nanocrystals, avoiding the appearance of the perovskite phase with narrower bandgap and resulting in a narrow emission and smooth morphology. As a result, blue PeLED with stable electroluminescent peak at 478 nm exhibits a maximum luminance of 227 cd/m 2 , a peak current efficiency of 0.35 cd/A and a maximum external quantum efficiency of 0.35%.