Steric Effects in Ruddlesden–Popper Blue Perovskites for High Quantum Efficiency

Ruddlesden–Popper perovskites (RPPs) feature enhanced stability compared to their bulk counterparts and attract attention for potential applications in light-emitting diodes (LEDs). However, to date, blue-emitting RPPs rely on halide compositional tuning, resulting in spectral shifts due to halide segregation under photo-/electrical-excitation. Here, efficient blue-emitting materials with single-halide RPPs using organic spacer engineering are reported. Experimental and computational results show that the (110)-oriented thin films exhibit larger bandgap and enhanced stability regardless of the choice of spacers, relative to the (100)-oriented RPPs. The correlation between the lattice structures and optoelectronic properties reveals that this new class of RPPs exhibits sky-blue emission at 483 nm with a quantum efficiency of ≈62%. Spearman correlation between the steric size of the spacers and the bandgap is estimated to be 92%, showing that the steric effect is crucial influencers. The protocol and strategy established in this study can be exploited to develop blue perovskite LEDs.