Humidity-Induced Reversible Crystallization of Laser-Printing Perovskite Quantum Dots in Glass

The complex and high-precision patterning of perovskite quantum dots (PeQDs) is of vital importance for exploring their new functionalities and device applications. In this work, a strategy based on the combination femtosecond (fs) laser-irradiation and humidity-control is reported to construct patterns of cyan CsPb(Cl/Br)(3) PeQDs in a transparent glass medium. Benefiting from their ionic crystal feature and low formation energy, CsPb(Cl/Br)(3) PeQDs can be locally crystallized and decomposed via fs laser irradiation without further heat-treatment. More notably, it is found that a water molecule is able to affect the growth of CsPb(Cl/Br)(3) PeQDs in glass. By modulation of relative humidity in air, the selectively decomposed perovskite structure is spontaneously regenerated, and the highly emissive CsPb(Cl/Br)(3) PeQDs can be in situ manufactured in the confined glass region. This allows for reversible luminescence from the same patterns of laser printing-erasing-recovering, and the process can be repeated for multiple cycles without destruction of optical performance and robustness. The results provide a flexible method to develop new encryption/decryption technology for information security and anti-counterfeiting.