Polymer passivation layers can improve the open-circuit voltage of perovskite solar cells when inserted at the perovskite–charge transport layer interfaces. Unfortunately, many such layers are poor conductors, leading to a trade-off between passivation quality (voltage) and series resistance (fill factor, FF). Here, we introduce a nanopatterned electron transport layer that overcomes this trade-off by modifying the spatial distribution of the passivation layer to form nanoscale localized charge transport pathways through an otherwise passivated interface, thereby providing both effective passivation and excellent charge extraction. By combining the nanopatterned electron transport layer with a dopant-free hole transport layer, we achieved a certified power conversion efficiency of 21.6% for a 1-square-centimeter cell with FF of 0.839, and demonstrate an encapsulated cell that retains ~91.7% of its initial efficiency after 1000 hours of damp heat exposure.

Silicon (Si) is generally considered as a poor photon emitter, and various scenarios have been proposed to improve the photon emission efficiency of Si. Here, we report the observation of a burst of the hot electron luminescence from Si nanoparticles with diameters of 150–250 nm, which is triggered by the exponential increase of the carrier density at high temperatures. We show that the stable white light emission above the threshold can be realized by resonantly exciting either the mirror-image-induced magnetic dipole resonance of a Si nanoparticle placed on a thin silver film or the surface lattice resonance of a regular array of Si nanopillars with femtosecond laser pulses of only a few picojoules, where significant enhancements in two- and three-photon-induced absorption can be achieved. Our findings indicate the possibility of realizing all-Si-based nanolasers with manipulated emission wavelength, which can be easily incorporated into future integrated optical circuits.

Semiconductor micro/nanowire is an attractive candidate for light-emitting devices (LED), especially laser diodes, due to its ideal geometric shape, excellent optical performance, and electrical transport properties. However, the realization of single micro/nanostructure semiconductor LED or lasers is still a challenge topic. In this Letter, we demonstrated a feasible route to fabricate electrically injection single microwire (MW) light-emitting devices. First, the excellent optical properties of single MW were investigated comprehensively, especially for the self-formed high-Q whisper gallery mode lasing. By properly engineering the band alignment of n-ZnO MW/p-GaN heterojunction using a dielectric MgO interlayer, the effective carrier injection and excitonic-type recombination electroluminescence was realized in the single MW active media. Our results present a significant step toward future fabrication of single micro/nanowire LED and laser diode.

Random lasing (RL) from self-constructed localized cavities based on micropits scatters in a single GaN microwire (MW) was investigated. The spectra and spatial resolution of RL exhibits that the lasing modes originated from different regions in the MW. Temperature-dependent lasing measurement of GaN RL shows an excellent characteristic temperature of about 52 K. In addition, the dependence of spatial localized cavities’ dimension on the pumping intensity profile and temperature was studied by fast Fourier transform spectroscopy. For GaN RL, the optical feedback was supported by localized paths through the scattering effect of micropits in the MW. The scattering feedback mechanism for RL can avoid the enormous difficulty in fabricating artificial cavity structures for GaN. Hence, the results in this paper represent a low-cost technique to realize GaN-based ultraviolet laser diodes without the fabrication difficulty of cavity facets.

The pursuit of compact lasers with low thresholds has imposed strict requirements on tight light confinements with minimized radiation losses. Bound states in the continuum (BICs) have been recently demonstrated as an effective mechanism to trap light. However, most reported BIC lasers are still bulky due to the absence of in-plane light confinement. Here, we combine BICs and photonic bandgaps to realize three-dimensional light confinements, as referred to miniaturized BICs (mini-BICs). We demonstrate highly compact active mini-BIC resonators with a record high-quality ( Q ) factor of up to 32,500, which enables single-mode lasing with the lowest threshold of 80 W/cm 2 among the reported BIC lasers. In addition, photon statistics measurements further confirm the occurrence of the stimulated emission in our devices. Our work reveals a path toward compact BIC lasers with ultralow power consumption and potentially boosts the applications in cavity quantum electrodynamics, nonlinear optics, and integrated photonics.