Lead-free perovskite Cs2AgBiBr6 manifests great potential in developing high-performance, environmentally friendly, solution-processable photodetectors (PDs). However, due to the relatively large energy bandgap, the spectrum responses of Cs2AgBiBr6 PDs are limited to the ultraviolet and visible region with wavelengths shorter than 560 nm. In this work, a broadband Cs2AgBiBr6 PD covering the ultraviolet, visible, and near infrared (NIR) range is demonstrated by incorporating titanium nitride (TiN) nanoparticles that are prepared with the assistance of self-assembled polystyrene sphere array. In addition, an atomically thick Al2O3 layer is introduced at the interface between the Cs2AgBiBr6 film and TiN nanoparticles to alleviate the dark current deterioration caused by nanoparticle incorporation. As a result, beyond the spectrum range where Cs2AgBiBr6 absorbs light, the external quantum efficiency (EQE) of the TiN nanoparticle incorporated Cs2AgBiBr6 PD is enhanced significantly compared with that of the control, displaying enhancement factors as high as 2000 over a broadband NIR wavelength range. The demonstrated enhancement in EQE arises from the photocurrent contribution of plasmonic hot holes injected from TiN nanoparticles into Cs2AgBiBr6. This work promotes the development of broadband solution-processable perovskite PDs, providing a promising strategy for realizing photodetection in the NIR region.

可溶液法制备的钙钛矿拥有优异的光学、电学性能，是一类极具潜力的电泵浦激光增益介质。近年来，基于钙钛矿材料的室温连续光泵浦激光以及大电流电致发光器件陆续被报道，在通向钙钛矿电泵浦激光的研究上取得了可喜进展，本文以此为主题展开综述。首先，介绍了钙钛矿材料实现电泵浦激光的优势。接着，梳理了现阶段通向钙钛矿电泵浦激光的两大问题，即非辐射复合损耗高和热效应严重，同时给出了改善这两大问题可采取的一些有效策略。然后，给出了电荷注入平衡化、降低光学损耗、促进粒子数反转等补充手段，它们有力推动了通向钙钛矿电泵浦激光研究向前发展。此外，还介绍了钙钛矿表面等离激元激光、钙钛矿激子极化激元激光等有望实现低阈值钙钛矿电泵浦激光的新机制。最后，总结全文，并对电泵浦钙钛矿激光未来研究做出了展望。

MAPbI3 perovskite has attracted widespread interests for developing low-cost near infrared semiconductor gain media. However, it faces the instability issue under operation conditions, which remains a critical challenge. It is found that the instability of the MAPbI3 nanoplatelet laser comes from the thermal-induced degradation progressing from the surface defects towards neighboring regions. By using PbI2 passivation, the defect-initiated degradation is significantly suppressed and the nanoplatelet degrades in a layer-by-layer way, enabling the MAPbI3 laser to sustain for 4500 s (2.7×107pulses), which is nearly three times longer than that of the nanoplatelet laser without passivation. Meanwhile, the PbI2 passivated MAPbI3 nanoplatelet laser with the nanoplatelet cavity displays a maximum quality factor up to ∼7800, the highest reported for all MAPbI3 nanoplatelet cavities. Furthermore, a high stability MAPbI3 nanoplatelet laser that can last for 8500 s (5.1×107pulses) is demonstrated based on a dual passivation strategy, by retarding the defect-initiated degradation and surface-initiated degradation simultaneously. This work provides in-depth insights for understanding the operating degradation of perovskite lasers, and the dual passivation strategy paves the way for developing high stability near infrared semiconductor laser media.

We report the Hong–Ou–Mandel (HOM) interference, with visibility of 91%, produced from two independent single photons retrieved from collective atomic excitations in two separate cold-atom clouds with high optical depths of 90. The high visibility of the HOM dip is ascribed to the pure single photon in the Fock state that was generated from a dense-cold-atom cloud pumping by a short pulse. The visibility is always the same regardless of the time response of the single-photon detectors. This result experimentally shows that the single photons retrieved are in a separable temporal state with their idler photons.