AI 中文总结
研究二维混合卤化物杂化钙钛矿中光开关光学功能，通过结合推挤弹性带和光力计算等方法，揭示光致卤离子交换源于强光-晶格耦合，建立无缺陷内在机制，还证明了无光时的内在自复位特性。
AI 中文摘要
卤化物钙钛矿中的离子迁移常与缺陷、不可逆过程和结构不稳定性相关，使其在光开关应用中实用性不大。本文展示了二维混合卤化物钙钛矿中可逆、无缺陷的光致卤离子交换的物理机制。发现卤离子交换过程源于强光-晶格耦合而非缺陷。通过结合推挤弹性带和光力计算表明，光致力执行非平衡功驱动卤离子沿卤交换路径移动但未达到完全交换构型。晶格动力学分析确定了一些软声子模式，其中两个具有约-0.14 e/(amu)$^{1/2}$的振子强度且为红外活性，可能是光致卤离子交换的微观起源。利用GW计算准确重现了无光时的光学吸收光谱，证明光照下光谱有明显红移，这是由于光致带隙重整化。这些发现不仅为二维混合卤化物钙钛矿中的光开关光学功能建立了无缺陷的内在机制，还证明了无光时的内在自复位特性。
英文摘要
Ion migration in halide perovskites is often associated with defects, irreversible processes, and structural instability, making them largely impractical for photo-switching applications. Here, we demonstrate a physical mechanism for reversible, defect-free light-induced halide-ion swapping in two-dimensional mixed-halide perovskites. We find that the halide-ion swapping process arises from strong light-lattice coupling rather than defects. By combining nudged elastic band and photo-force calculations, we show that photo-induced forces perform non-equilibrium work that drives halide ions along the halide-exchange path without reaching the fully swapped configuration. Thus, the cumulative light-induced work can only partially overcome the ground-state activation energy barrier in the presence of light. Analysis of lattice dynamics identifies a few soft phonon modes, two of which are IR-active with oscillator strength $\approx -0.14$ e/(amu)$^{1/2}$, which may be considered the microscopic origin of light-induced halide-ion swapping. This microscopic origin is further supported by band-edge-selective electron-phonon coupling, which amplifies interactions among excited carriers under illumination and with halide-ion motion without inducing a uniform dynamical instability. Using GW (G-Green's function and W-screened Coulomb interaction) calculations, we accurately reproduce the experimentally observed optical absorption spectra in the absence of light, enabling us to describe the light-induced excited state reliably. We demonstrate a clear redshift in the optical spectra in the presence of light, which is due to light-induced bandgap renormalization. Overall, these findings not only establish an intrinsic, defect-free mechanism for photoswitchable optical functionality in 2D mixed-halide perovskites but also demonstrate an intrinsic self-resetting feature in the absence of light.
Comments16-page manuscript with supporting information
