Composition‐Graded Perovskite Microwire Toward Broad Wavelength Tunable Single‐Mode Lasing.

Continuously manipulating the resonant wavelength of lasing modes within a large spectral range is of great significance for expanding device functionality. Here, to synthesize a single CsPbClxBr3‐x perovskite microwire with the energy bandgap gradient spanning from 2.33 to 2.83 eV along the length direction defined as the axis by using the vapor‐phase anion exchange method is proposed. A high‐quality (≈103), wide range (≈60 nm), and continuously tunable single‐mode laser is achieved in as‐prepared perovskite microwire alloy, which provides both gain media and microresonator. Simultaneously, the exciton recombination dynamics and atomic‐scale interdiffusion mechanisms at different components are clarified through time‐resolved photoluminescence (PL) spectra and theoretical calculations. The vacancy defects have a significant impact on the interdiffusion of halogen anions, excitonic recombination lifetime, and fluorescence quantum efficiency. The work provides a new strategy for the construction of new‐type broadband tunable lasers and high‐precision microspectrometers. [ABSTRACT FROM AUTHOR]