General phase segregation and phase pinning effects in lanthanide-doped lead halide perovskite with dual-wavelength lasing.

A strategy of lanthanide-ion doping into dual-halogen-alloyed perovskites CsPb(XxY1-x)3 (X, Y = Cl, Br, I) via chemical vapor deposition is introduced, obtaining a series of high-quality, stable microplates. Under continuous light excitation, each sample exhibits highly stable dual-band photoluminescence emission, whereby pairwise combinations of the three halogens enable photoluminescence to cover the red, green, and blue spectral regions. Corresponding high-performance dual-wavelength lasers are achieved. The segregated phase domains are tens of nanometers in size with well-defined boundaries. Theoretical calculations indicate that lanthanide-ion doping promotes phase segregation and facilitates ion migration in the alloyed case, while suppressing it in the phase-segregated state, producing a phase-pinning effect. This mechanism imposes opposite trends on the migration barrier in alloyed versus deployed domains, simultaneously driving halide segregation and pinning ion migration in segregated phases. Our work simultaneously enhances stability and broadens the bandgap-engineering for lead-halide perovskites, accelerating their entry into next-generation optoelectronics.