The performance of inverted perovskite solar cells critically depends on the molecular contact formed by hole-selective self-assembled molecules. Conventional single-component hole-selective self-assembled molecules are prone to structural collapse under external stress, which disrupts hole transport and accelerates device degradation. Here we develop high-entropy molecular contacts (HE-MCs) by using a ternary blend of carbazole-naphthalene self-assembled molecules to simultaneously enhance device efficiency and operational stability. By blending molecules with similar chemical structures but distinct intermolecular interactions and packing motifs, we increase the packing-mode diversity to form a high-entropy system that affords efficient hole extraction and robust interfaces. Single-crystal analysis, molecular dynamics simulations and interfacial characterizations collectively confirm the successful formation of HE-MCs and their substantially improved resilience to external stress. Perovskite solar cells incorporating HE-MCs achieve a champion power conversion efficiency of 27.50% (certified steady-state efficiency of 27.31%) and extended operational stability under various accelerated ageing tests, with negligible efficiency loss after 1,300 h under maximum power point tracking at 85 °C in ambient air. Our strategy provides a broadly applicable framework that exploits high entropy in packing modes for high-performance interfaces in perovskite photovoltaic devices. High-entropy molecular contacts made by blending self-assembled molecules improve hole transport through diverse packing modes. Solar cells incorporating these contacts achieve a certified power conversion efficiency of 27.31% and negligible loss after 1,300 h of operation at 85 °C.
Coherent control uses interference between quantum pathways to enhance or suppress transitions to a target quantum state. In stimulated Raman excitation, such control can be achieved through interference between two indistinguishable pathways connecting the same initial and final states, with the relative phase between the pathways modulating the population transfer to the final state. Extending this strategy to the extreme ultraviolet (XUV) and X-ray regimes would enable control of ultrafast electronic dynamics and site-selective core excitations. However, Raman coupling at short wavelengths competes with photoionization and intermediate-state decay, whereas intense fields with stable and adjustable relative phases remain difficult to produce. Here we use two-colour pulses from a seeded coherent free-electron laser to excite helium from its ground state to a bound metastable state via stimulated XUV Raman excitation. We implement phase-coherent control by creating two interfering Raman pathways through the ionization continuum and modulate the transferred population by varying their relative phases. Blocking one pathway removes the modulation, confirming its interferometric origin, and time-dependent Schrödinger equation calculations reproduce the measured phase dependence. Our results establish phase-controlled stimulated Raman excitation in the XUV regime, providing a strategy for the coherent control of atomic and molecular processes at short wavelengths. Researchers modulate population transfer from the helium ground state to a metastable state by controlling the relative phase between two interfering stimulated Raman pathways through the continuum, demonstrating phase-coherent control in the extreme ultraviolet.
Optical circulators are a key component for optical systems, routing light between ports to manage signal flow and protect components from back-reflection. As integrated photonics advances towards chip-scale systems, incorporating key optical building blocks on chip is increasingly important. Optical circulators have been slow to follow this process. Although conventional circulators break Lorentz reciprocity using magneto-optic materials, they are impractical to integrate into devices. Here we realize a broadband electro-optic travelling-wave optical circulator based on thin-film lithium niobate that achieves non-reciprocity without magnetic materials, resonant structures or wavelength conversion. Our architecture uses cascaded travelling-wave Mach–Zehnder modulators driven by electrical sinusoidal signals, achieving up to 37 dB peak isolation, spanning the full O- and C+L optical telecom bands (14 THz bandwidth). The device shows excess losses of 0.1 dB (port 1 to 2) and 4.9 dB (port 2 to 3), with 0.84 dB of passive losses. To demonstrate practicality, we deploy this circulator in same-wavelength, bidirectional coherent transmission, achieving 400G/polarization with industry-compliant hardware, digital signal processing and forward-error-correction codes. These results establish a scalable route to broadband on-chip circulation, with relevance to industry-standard optical fibre transmission systems and position electro-optic non-reciprocity as a manufacturable, foundry-compatible building block for the next generation of integrated optical transceivers. A thin-film lithium niobate integrated circulator with peak isolation up to 37 dB and a broad transmission bandwidth supports bidirectional transmission through single-mode fibre at 800G standard throughput.
Harnessing the full dimensionality of light by coupling its spatial and temporal degrees of freedom offers a powerful means to engineer optical fields with diverse functionalities. Such space–time structured light fields—ranging from localized wave packets to spatiotemporal vortices—hold promise for transforming ultrafast science, laser machining, imaging and optical communications. However, their realization has so far relied on complex free-space configurations, requiring bulky components such as gratings and spatial light modulators placed in Fourier-conjugate planes. Here we introduce a chip-scale platform that generates space–time wave packets directly from a laser array, bridging the gap between structured light physics and integrated photonics. Our design uses distributed feedback lasers with dual-ended geometries that produce mutually coherent sub-beams with stable phase contrasts. This versatile architecture enables precise control of spatial–spectral correlations, allowing the synthesis of incoherent or coherent space–time wave packets with scalable width and propagation length. By uniting field structuring and lasing within a single device, this approach opens a pathway towards integrated light sources capable of on-chip beam shaping, combining and spatiotemporal control, with far-reaching implications in microscopy, tomography, communications and ultrafast optical technologies. An integrated semiconductor laser array can directly generate incoherent space–time wave packets with propagation-invariant and self-healing characteristics.
Organic polymers that are highly transparent, ductile and lightweight are very attractive for optical applications. However, at present, the capabilities of all-organic polymers lag far behind their inorganic analogues due to their lower refractive index (n) (n ≈ 1.4–1.6) and poor infrared transparency. Here we report a high-refractive-index (n ≈ 2.53 at 750 nm) all-organic polymer (K153) with unique cyano substitutions, which possesses a much higher refractive index than inorganic chalcogenide glasses and CdS/ZnS/ZnSe (>2.25). Moreover, K153 exhibits outstanding infrared transparency, owing to the symmetric architectures of constructing units that reduce infrared light losses. The underlying mechanism behind the high n value of K153 is attributed to its larger polarization and enhanced intermolecular interactions induced by linear cyano groups. Furthermore, superiorities of K153 films including impressive environmental tolerance, opportunities for high-quality infrared imaging, extraordinary flexibility, tunable n values via chemical doping and nanoimprint ability were also demonstrated. The results not only provide a very competitive n for infrared-transparent organic polymers over inorganic materials but also demonstrate that tailored cyano engineering can optimize the molecular structure effectively, culminating in a dramatic increase in n and a step towards the use of all-organic polymers for infrared applications. An organic polymer with a large refractive index and excellent transparency in the infrared regime could bring new opportunities for imaging.
