Color imaging experiment demonstrates a photochromic behavior of mixed-halide perovskites upon dark and light excitation, while the color emitted by the crystals changes from red to yellow and vice versa with the intensity of excitation light source. Unlike the photochromic property commonly observed in solution-state polymer materials, solid-state perovskite materials with photochromic behavior might open wide applications in consumer products and electronic devices. In the next part, we report on a reversible photoluminescence (PL) peak in iodide-based organic-inorganic lead halide perovskite materials under a 2-photon absorption process, while tuning the excitation wavelength. Intriguingly, two shorter wavelength peaks are visible and become prominent when the excitation photon energy is being tuned in the high energy spectrum, while laser power is remained constant. The same phenomenon of reversible PL peak is also observed in various iodine-based organic-inorganic halides as well as all-inorganic perovskite single crystals and polycrystals. We attribute to the reversible PL peak phenomenon to the photoinduced structural deformation and the associated change in the optical bandgap of iodide perovskites under the femtosecond laser excitation. Our findings will introduce a degree of freedom in future research as well as adding functionalities to optoelectronic applications in these emerging perovskite materials-based devices.

彩色成像实验证明了混合卤化物钙钛矿在暗光和光激发下的光致变色行为，而晶体发出的颜色随着激发光源的强度从红色变为黄色，反之亦然。与溶液态聚合物材料中常见的光致变色特性不同，具有光致变色行为的固态钙钛矿材料可能会在消费产品和电子设备中广泛应用。在下一部分中，我们报告了基于碘化物的有机-无机卤化铅钙钛矿材料在 2 光子吸收过程中的可逆光致发光 (PL) 峰，同时调整激发波长。有趣的是，当激发光子能量在高能谱中被调谐时，两个较短波长的峰是可见的并且变得突出，而激光功率保持不变。在各种碘基有机无机卤化物以及全无机钙钛矿单晶和多晶中也观察到相同的可逆 PL 峰现象。我们将可逆 PL 峰现象归因于光致结构变形和飞秒激光激发下碘化物钙钛矿光学带隙的相关变化。我们的发现将在未来的研究中引入一定程度的自由度，并为这些新兴的钙钛矿材料器件中的光电应用增加功能。我们将可逆 PL 峰现象归因于光致结构变形和飞秒激光激发下碘化物钙钛矿光学带隙的相关变化。我们的发现将在未来的研究中引入一定程度的自由度，并为这些新兴的钙钛矿材料器件中的光电应用增加功能。我们将可逆 PL 峰现象归因于光致结构变形和飞秒激光激发下碘化物钙钛矿光学带隙的相关变化。我们的发现将在未来的研究中引入一定程度的自由度，并为这些新兴的基于钙钛矿材料的器件中的光电应用增加功能。