Thermal evaporation of perovskite films holds considerable promise for the scalable manufacturing and pixel patterning of perovskite light-emitting diodes (PeLEDs). However, the performance of evaporated PeLEDs remains inferior to their solution-processed counterparts due to the lack of effective strategies to regulate perovskite crystallization during vacuum deposition. Here we address this challenge and achieve precise control over crystallization pathways. Dual-amide additives suppress premature perovskite phase formation during deposition and decelerate crystallization kinetics during post-annealing. We realize thermally evaporated near-infrared PeLEDs with a maximum external quantum efficiency of 25.0% for emission at 805 nm, and a T50 lifetime of 23 h at a driving current density of 100 mA cm−2. To show the advantages of thermal evaporation in pixelization, we realize monolithic dual-colour-emitting PeLEDs at 805 nm and 759 nm by integrating different PeLEDs on the same substrate and demonstrate dual-wavelength wearable pulse oximetry. This work provides insights into vacuum deposition crystallization dynamics and establishes a crystallization regulation methodology to advance evaporated perovskite optoelectronics. Dual-amide additives regulate the crystallization of thermally evaporated perovskites, enabling near-infrared perovkite LEDs with a peak external quantum efficiency of 25.0%, highlighting their potential for scalable pixelated optoelectronics.
Light-emitting diodes (LEDs), with pixel sizes ranging from the millimetre to micrometre scale, have driven advances in display technologies for large-area panels, portable devices and wearable platforms. As applications expand beyond conventional displays to optical sensing, implantable optogenetics, on-chip optical interconnects and super-resolution microscopy, demand is growing for ultracompact, energy-efficient light sources capable of subwavelength and spatiotemporal control. Nanoscale light-emitting diodes (nano-LEDs) stand out as promising candidates to address these requirements, offering exceptional control over light generation, confinement and emission dynamics. Here we discuss recent progress in colloidal quantum dots and perovskite nano-LED technologies across material chemistry, device engineering and nanofabrication strategies. We also propose future research directions for harnessing nano-LEDs in emerging applications, underscoring their potential to move beyond traditional optoelectronic functions. Far beyond a miniaturized extension of conventional LEDs, nano-LEDs are poised to become a transformative platform uniting optoelectronics, nanophotonics and device engineering. This Review covers recent advances in quantum dots and perovskite nano-LEDs, discusses the challenge of balancing efficiency, stability and full-colour integration, and highlights potential future applications.
In homogeneous materials, scattered light propagates predominantly in the forward direction; thus, collecting signal on the illumination side often relies on interfaces, disorder or multiple scattering. Nonlinear wave mixing can relax this constraint by combining the directions of the driving fields. If the generated wavelength is longer than the driving wavelengths, intrinsic backward emission can become efficient. Here we exploit this regime using coherent Stokes Raman scattering to generate signal directly into the backward hemisphere. Simulations pinpoint high-numerical aperture geometries and polarization states that maximize backward emission, and experiments confirm backward signals from liquids and tissues with detected levels approaching the strength of forward-detected coherent Raman signals. Because the generated signal originates at the focus and remains refocusable, it enables coherent Raman microscopy with same-side confocal collection compatible with fibre coupling and spectrometers when transmission access is impractical. The approach is particularly relevant and beneficial for samples on opaque substrates, thick specimens, tissue biopsies and fibre- or spectrometer-based implementations. Backscattered coherent Raman microscopy brings new opportunities.
The promises of halide perovskites for chiroptical and spintronic applications hinge largely on how long their spin coherence can last. Recent demonstrations of spin injection from chiral single quantum wells to achiral semiconductors have enabled a variety of spin functionalities. However, their spin polarization at the device level remains limited due to rapid interfacial and bulk spin losses. Here we demonstrate a spin cascade strategy by constructing oriented perovskite chiral multiple quantum wells to extend the spin lifetime. In chiral multiple quantum wells, quantum wells with varying well widths exhibit intrinsic and continuous chirality across all quantum-well phases with an average circular dichroism dissymmetry factor of 1.5 × 10−2. In this system, slowly energy-varying and spatially coupled chiral multiple quantum wells establish consecutive intermediate polarization states for spin cascade, thereby extending the spin coherence lifetime to ~5 ns at room temperature. The long-lived spin coherence yields circularly polarized luminescence with a luminescence dissymmetry factor (|glum|) of 1.4 × 10−2 and spin-dependent charge transport with a polarization degree of over 80%, enabling efficient X-ray-triggered dissymmetric photopolymerization and high-performance circularly polarized light photodetectors. This work opens the way to long-lived spin coherence in halide perovskites, promoting their use in chiroptical and spintronic devices. Chiral multiple quantum wells enhance spin coherence in perovskites through spin cascade, achieving over 5-ns spin lifetime at room temperature.
Interfacial non-radiative recombination, particularly at the C60 electron-selective contact, remains a major bottleneck limiting the performance of inverted perovskite solar cells. While previous efforts have primarily focused on passivating trap states at the perovskite surface, the underlying mechanism by which fullerene-based electron transport layers induce interfacial recombination has remained unclear. Here we reveal that C60 lowest unoccupied molecular orbital (LUMO)-derived band-like states arising from strong intermolecular coupling within the C60 film drive recombination at the perovskite/C60 interface. To mitigate this issue, we develop a vapour-phase molecular passivation strategy using trialkylamines to disrupt C60 molecular packing, substantially weakening the C60 LUMO-derived band-like states and suppressing interfacial non-radiative losses. The trialkylamine treatment minimizes the quasi-Fermi-level splitting loss after C60 deposition from 89 meV to 41 meV, and to 17 meV in conjunction with standard surface passivation. This interfacial modulation enables inverted perovskite solar cells with a certified power conversion efficiency of 27.2% (stabilized 26.6%) on a 1.02 cm2 active area. The devices also retain over 98% of their initial efficiency after 1,000 h of continuous illumination under ambient air conditions. Our work resolves the long-standing puzzle of why C60 induces severe interfacial recombination and guides the design of comprehensive interface passivation strategies towards efficient perovskite photovoltaics. Interfacial recombination in perovskite solar cells is mitigated through a vapour-phase molecular passivation method using trialkylamines, disrupting C60 packing. This approach results in a power conversion efficiency of up to 27.2% while maintaining stability.
