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Abstract The high transmission speed of optical signals and their application in optical computation have created a growing demand for photon‐programmed memory devices. Rather than using electrical pulses to store data in one of two states, the photomemory (PM) devices exploit the optical stimulation to store the light information. In this work, the application of a nonvolatile rewritable PM array using the photochromic inorganic perovskite CsPbIBr₂grown by a vapor‐deposition process is demonstrated. Reversible phase transitions between orthorhombic (δ) and cubic (α) phases are achieved in CsPbIBr₂films through laser‐induced heat and moisture exposure. The PM pixels in an optically absorbing perovskite phase exhibit ≈50‐fold photoresponsivity as large as those in a transparent‐colored non‐perovskite phase. Storing optical data are achieved by heating pixels through a near‐infrared laser, while moisture exposure is used to erase the stored information. The nonvolatile PM array exhibits great write‐read‐erase cycle endurance and data retention capability without obvious performance degradation after storage in air for one week. This work demonstrates the promising application of vapor‐deposited inorganic perovskite for optical information storage and the unique potential of them for use in optical switches, tunable metasurfaces, and many other applications. 

A green‐emitting perovskite first‐order distributed feedback (DFB) laser based on the methylammonium lead bromide (MAPbBr₃) with high stability is demonstrated for the first time. The laser achieves stable lasing at 550 nm with a full width at half maximum of 0.4 nm. Low lasing threshold of 60 μJ cm⁻²under nanosecond pulsed excitation and 3.1 μJ cm⁻²under femtosecond pulsed excitation is observed, showing a much lower lasing threshold compared with the second‐order DFB cavities, which are fabricated on the same substrate. By optimizing the antisolvent treatment and encapsulating with poly(methyl methacrylate), the laser lifetime, resistance to moisture, lasing threshold, and intensity are significantly improved. The lasers are fabricated with a complementary metal‐oxide‐semiconductor‐compatible process, thus offer promising potential for the integrated photonic devices. 

Metal halide perovskite light-emitting diodes (PeLEDs) have experienced a rapid advancement in the last several years with the external quantum efficiencies (EQEs) reaching over 20%, comparable to the state-of-the-art organic LEDs and quantum dot LEDs. The photoluminescence quantum yields of perovskite films have also been approaching 100%. Therefore, the next step to improving the EQE of PeLEDs should be focused on boosting light extraction. In this Letter, we demonstrate the emitter dipole orientation as a key parameter in determining the outcoupling efficiency of PeLEDs. We find that the ${\mathrm{C}\mathrm{s}\mathrm{P}\mathrm{b}\mathrm{B}\mathrm{r}}_3$emitter has a slightly preferred orientation with the horizontal-to-vertical dipole ratio of 0.41:0.59, as compared to 0.33:0.67 in the isotropic case. A theoretical analysis predicts that a purely anisotropic perovskite emitter may result in a maximum EQE of 36%. 

In this paper, we demonstrate a new method to pattern perovskites using a dry lift-off process. By utilizing parylene-C as a sacrificial layer, patterns with <12 um features and multi-color patterns can be achieved.