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The application of solar-thermal surfaces for antifrosting and defrosting has emerged as a passive and environmentally friendly approach to mitigate the negative consequences of frost formation, such as structural damage and reduced heat transfer efficiency. However, achieving robust all-day frostphobicity solely through interfacial modification and solar-thermal effects is challenging in practical applications: The thick frost that accumulates at night strongly scatters solar radiation, rendering the solar-thermal coatings ineffective during the daytime. Additionally, these nanostructured coatings are susceptible to wear and tear when exposed to the outdoors for extended periods of time. To address these challenges, we present an innovative frostphobic surface that incorporates V-grooved structures with superhydrophobic solar-thermal layers (VSSs). The out-of-plane gradient structures facilitate spatially regulated vapor diffusion, an enhanced photothermal effect, and robust water repellency. These features not only prevent frost from covering the entire surface overnight, enabling effective solar-thermal defrosting during the daytime, but also protect the surface from deterioration. The combined merits ensure robust all-day frostphobicity and exceptional durability, making the VSS surface promising for practical applications and extending the lifespan in extreme environments.

All-polymer solar cells (all-PSCs) have seen rapid progress enabled by the development of high-performance polymer acceptors. Most polymer acceptors are based on the monomers of a classic small molecular acceptor (SMA) named Y6 by polymerizing at the position of the end groups, forming an “end-to-end” linkage. In this work, we report a completely different “core-to-core” linking mode by polymerizing the Y-series monomers at the central core position instead. This innovative strategy results in a drastically altered molecular configuration that resembles a “double decker,” with intramolecular packing between different monomer units in the same polymer. The overall molecular packing is improved, benefiting charge delocalization and charge transport. As a result, the PffBQx-T-based ternary blend achieved an outstanding efficiency of 18.7%, attributed to the enhanced absorption response, improved packing, and efficient charge dynamics. Our work demonstrates a novel polymer design rationale that serves as a promising avenue toward highly efficient and stable all-PSCs.

Rapid hot-carrier/exciton cooling constitutes a major loss channel for photovoltaic efficiency. How to decelerate the hot-carrier/exciton relaxation remains a crux for achieving high-performance photovoltaic devices. Here, we demonstrate slow hot-exciton cooling that can be extended to hundreds of picoseconds in colloidal HgTe quantum dots (QDs). The energy loss rate is 1 order of magnitude smaller than bulk inorganic semiconductors, mediated by phonon bottleneck and interband biexciton Auger recombination (BAR) effects, which are both augmented at reduced QD sizes. The two effects are competitive with the emergence of multiple exciton generation. Intriguingly, BAR dominates even under low excitation fluences with a decrease in interparticle distance. Both experimental evidence and numerical evidence reveal that such efficient BAR derives from the tunneling-mediated interparticle excitonic coupling induced by wave function overlap between neighboring HgTe QDs in films. Thus, our study unveils the potential for realizing efficient hot-carrier/exciton solar cells based on HgTe QDs. Fundamentally, we reveal that the delocalized nature of quantum-confined wave function intensifies BAR. The interparticle excitonic coupling may cast light on the development of next-generation photoelectronic materials, which can retain the size-tunable confinement of colloidal semiconductor QDs while simultaneously maintaining high mobilities and conductivities typical for bulk semiconductor materials.

Various phosphonic acid based self-assembled monolayers (SAMs) have been commonly used for interface modifications in inverted perovskite solar cells. This typically results in significant enhancement of the hole extraction and consequent increase in the power conversion efficiency. However, the surface coverage and packing density of SAM molecules can vary, depending on the chosen SAM material and underlying oxide layer. In addition, different SAM molecules have diverse effects on the interfacial energy level alignment and perovskite film growth, resulting in complex relationships between surface modification, efficiency, and lifetime. Here we show that ethanolamine surface modification combined with [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) results in significant improvement in device stability compared to devices with 2PACz modification only. The significantly smaller size of ethanolamine enables it to fill any gaps in 2PACz coverage and provide improved interfacial defect passivation, while its different chemical structure enables it to provide complementary effects to 2PACz passivation. Consequently, the perovskite films are more stable under illumination (slower photoinduced segregation), and the devices exhibit significant stability enhancement. Despite similar power conversion efficiencies (PCE) between 2PACz only and combined ethanolamine-2PACz modification (PCE of champion devices ∼21.6–22.0% for rigid and ∼20.2–21.0% for flexible devices), the T80lifetime under simulated solar illumination in ambient is improved more than 15 times for both rigid and flexible devices.

Sn-based perovskites are promising thin-film photovoltaic materials for their ideal bandgap and the eco-friendliness of Sn, but the performance of Sn-based perovskite solar cells is hindered by the short carrier diffusion length and large defect density in nominally-synthesized Sn-based perovskite films. Herein we demonstrate that a long carrier diffusion length is achievable in quasi-2D Sn-based perovskite films consisting of high-member low-dimensional Ruddlesden—Popper (RP) phases with a preferred crystal orientation distribution. The key to the film synthesis is the use of a molecular additive formed by phenylethy-lammonium cations and optimally mixed halide—pseudohalide anions, which favorably tailors the quasi-2D Sn-based perovskite crystallization kinetics. The high-member RP film structure effectively enhances device short-circuit current density, giving rise to an increased power conversion efficiency (PCE) of 14.6%. The resulting device demonstrates a near-unity shelf stability upon 1,000 h in nitrogen. A high reproductivity is also achieved with a count of 50 devices showing PCEs within a narrow range from minimum 13.0% to maximum 14.6%.

We investigate the charge carrier dynamics in HgTe quantum dots emitting in the second near-infrared window (1000–2500 nm). To provide a link between fundamental physics and practical application, we made consistent studies of the charge carrier dynamics evolution for quantum dots in different states: colloidal solutions of quantum dots capped with a long-chain ligand; thin films made from them; and finally, exchanged to short-chain ligand films suitable for field effect transistor based devices. Ultrafast transient absorption spectroscopy reveals an ultralow Auger-related nonradiative relaxation threshold at 0.1 exciton per quantum dot, both in colloidal solutions and solid films, with a rate of 30 ns–1. The exchange from long- to short-chain ligands causing closer packing of the HgTe quantum dots leads to a strong increase of the Auger recombination rate of up to 100 ns–1. The competition between the Auger process and excitonic recombination significantly affects the performance of HgTe-based thin film photodetectors operating at room temperature, resulting in a 2 orders of magnitude drop in responsivity when the excitation flux was increased from 0.01 to 5 W·cm–2.

All-polymer solar cells (APSCs) are one of the most promising types of application-oriented photovoltaic technologies because they are operationally and mechanically stable; however, their low power conversion efficiency (PCE) restricts the core competitiveness against other types of solar cells. Besides, poor insight of mechanical performance, such as ductility, has been revealed for cutting-edge APSCs. Herein, we chose two well miscible polymer donors, PM6 and J71, and achieved a PCE of 16.52% for APSCs in a ternary blend with PY-IT and 15.74% for air-processed devices. The improvement is enabled by effective energy transfer, tuned crystallinity, and improved phase separation, which resulted in faster charge transfer and more balanced charge transport, suppressed exciton recombination, and more efficient charge extraction. Furthermore, the good miscibility between two donors enabled the target to have well-maintained film morphology without damaging the initial nanoscale network, bringing comparable film ductility. Last, the inner structure-property relationship of photovoltaic and morphological parameters, and film ductility was illustrated by a correlation study.

Organic radicals are unstable and stable radicals usually display non-luminescent properties. Luminescent radicals possess the all-in-one properties of optoelectronics, electronics, and magnetics. To date, the reported structures of luminescent radicals are limited to triphenylmethyl radical derivatives and their analogues, which are stabilized with extended π-conjugation. Here, we demonstrate the first example of a nonconjugated luminescent radical. In spite of the lack of delocalized π-stabilization, the radical polymer readily emits red luminescence in the solid state. A traditional luminescent quencher, 2,2,6,6-tetramethylpiperidin-1-yl turned into a red chromophore when grafted onto a polymer backbone. Experimental data confirm that the emission is associated with the nitroxide radicals and is also affected by the packing of the polymer. This work discloses a novel class of luminescent radicals and a distinctive pathway for luminescence from open-shell materials.

Considering that the periodic photonic nanostructures are commonly realized by expensive nanofabrication processes and the tunability of structure parameters is limited and complicated, we demonstrate a solution-processed upside-down molding method to fabricate photonic resonators on perovskites with a pattern geometry controllable to a certain extent. This upside-down approach not only reveals the effect of capillary force during the imprinting but also can control the waveguide layer thickness due to the inversion of the perovskite membranes.

There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B←N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.

Blue-emitting lead halide perovskite nanocrystals (NCs) continue to exhibit unstable emission spectra, resulting from halide migration effects that hinder the performance of blue NC light-emitting diodes (NC-LEDs). One method to avoid halide mixing while still attaining deeper blue emission with improved stability is to incorporate rubidium into the mixture of A-site ions. Here, we explore the impact of varying the amount of rubidium doping in lead halide perovskite NCs. Our findings indicate that the rubidium-doping ratio influences the number of defects in the perovskite NCs, ultimately affecting the degree of blue shift we observe and the resulting performance of the NC-LEDs. Additionally, this study presents a modified room-temperature, open-air synthesis of sky-blue perovskite CsxRb1–xPbBr3NCs with 0 to 45% Rb-alloying. The synthesized NCs have sizes ranging from 13.0 to 15.6 nm, and their emission can be adjusted from 515 to 496 nm with an observed full width at half-maximum of between 19 and 26 nm. These NCs also demonstrate a high photoluminescence quantum yield ranging from 94.5 to 69.7%. The NC-LEDs fabricated from these NCs showed stable spectra, a maximum external quantum efficiency (EQE) of 11.0% with a peak luminescence of 32,300 cd/m2at 508 nm for green emission, and a maximum EQE of 5.9% with a peak luminescence of 21,700 cd/m2at 496 nm for sky-blue emission. These results highlight the potential of Rb-alloying lead halide perovskite NCs for developing efficient and spectrally stable blue perovskite NC-LEDs.

Realizing efficient on-chip light sources on Si is a crux for Si-based photonic integrated circuits (PICs). Lateral aspect ratio trapping (LART) by MOCVD for selective epitaxy of III–V materials on (001) silicon-on-insulator (SOI) is a promising technique for monolithic integration of light sources on silicon and deployment of Si-based PICs. In this report, a monolithic microscaled GaAs/Si platform is obtained through the selective growth of GaAs membranes on industry-standard (001)-oriented SOI wafers by the LART technique. The GaAs membranes are laterally grown from {111}-oriented Si surfaces inside patterned oxide trenches, with dimensions defined by lithography. GaAs microdisk lasers (MDLs) fabricated on the GaAs membranes laterally grown on (001) SOI lase at room temperature (RT) by optical pumping. RT-pulsed lasing was achieved with a threshold of 880 μJ/cm2. This work provides a crucial step toward fully integrated Si photonics.

Current non-fullerene organic photovoltaics (OPVs) can achieve high photocurrent generation yields with small donor/acceptor energy offsets. However, the effect of varying energy offset on the charge dynamics in these systems is not fully understood. Here, we use optical spectroscopy to probe charge dynamics in three model non-fullerene systems with varying energy offsets. We find that systems with marginal and negative energy offsets show low photocurrent generation yields and significant radiative recombination from the exciton state. Improved photocurrent generation and suppressed exciton emission is observed when the device is under reverse bias. Our results indicate that photoexcitation of these systems leads to bound charge pairs at the donor/acceptor interface which tend to recombine via the singlet exciton state unless their separation is facilitated by external electric fields. Our results shed light on the charge separation and recombination dynamics in non-fullerene OPVs with small donor/acceptor energy offsets.

Multi-component organic solar cells (OSCs) comprising more than two donor and acceptor materials have attracted significant research attention, as they can offer broader and better absorption, hence increasing solar cell performance. However, the morphology of multi-component OSCs is exceptionally complicated and challenging to control. Here, we develop a highly efficient (near 17.7%) quaternary OSC (q-OSC) using two polymer donors (namely PM6 and PTQ10) along with a fullerene (PC71BM) and a non-fullerene acceptor (N3). Our quaternary system demonstrates a new type of “rivers and streams” functional hierarchical (multi-length scale) morphology, where small domains of PTQ10 and PC71BM act as separators that spatially separate PM6 and N3, which effectively suppressed charge recombination, enhanced hole transport, and balanced charge transportation. These improvements in the quaternary system contribute to the increased internal quantum efficiency (IQE) and, thus, lead to an excellent JSCand device performance, which surpass their respective binary and ternary OSCs.

Lead halide perovskite nanocrystals (NCs) have shown remarkable properties for emission applications, but their toxicity and instability are a hindrance to many commercial uses. Herein, we report the synthesis of lead-free all-inorganic Cs3Cu2X5(X = I, Br/I, Br, Br/Cl, Cl) colloidal nanocrystals as members of the metal–metal halide family of materials. These nanocrystals have uniform sizes less than 10 nm in diameter and show excellent optical properties, including composition-tunable emission spectra over the spectral region of 440–530 nm; high photoluminescence quantum yields of ∼100, 20, and 30% for X = Cl, Br, and I, respectively; and large effective Stokes shifts of over 100 nm for all species. Nanocrystals are synthesized by a room temperature, antisolvent method, but the precursors and ligands are also shown to be effective in hot -injection synthesis. Pure- and mixed-halide materials show tunable emission with the halide concentration, with a large fwhm of 80–110 nm due to a widely reported exciton self-trapping emission mechanism. Notably, the Cu3Cu2Cl5NCs exhibit a near-unity quantum yield with an emission at 520 nm, high crystallinity, and good stability. These materials can be processed and maintained in adequately stable dispersions to enable inkjet printing of these materials into arbitrary patterns. These results indicate that cesium copper chloride NCs may have great potential for the future display or lighting applications.

The emergence of indoor electronic devices for internet of things (IoT) has motivated the scientific community to develop photovoltaic devices that can efficiently convert indoor light into electricity. In this paper, we report high-efficiency non-fullerene organic photovoltaic (OPV) cells with over 30% power conversion efficiency (PCE) under indoor conditions. Our results show that the choice of electron-transporting layer (ETL) is critically important to enable such performance. The use of an ETL (named PDI-NO) with a deep highest occupied molecular orbital (HOMO) level can effectively suppress leakage current and reduce trap-assisted recombination of the devices. Thus, using this ETL, we achieve record PCE of 31% by utilizing a low-band-gap acceptor in the bulk-heterojunction (BHJ) blend. Whereas, in another case, by employing a large-band-gap acceptor, a PCE of 26.7% with over 1V is achieved. Our study paves the way toward high-performance indoor OPV devices for powering IoT electronics.

Efficient III-V lasers directly grown on Si remain the “holy grail” for present Si-photonics research. In particular, a bufferless III-V laser grown on the Si-photonics 220 nm silicon-on-insulator (SOI) platform could seamlessly bridge the active III-V light sources with the passive Si-based photonic devices. Here we report on the direct growth of bufferless 1.5 µm III-V lasers on industry-standard 220 nm SOI platforms using metal organic chemical vapor deposition (MOCVD). Taking advantage of the constituent diffusivity at elevated growth temperatures, we first devised a MOCVD growth scheme for the direct hetero-epitaxy of high-quality III-V alloys on the 220 nm SOI wafers through synergizing the conventional aspect ratio trapping (ART) and the lateral ART methods. In contrast to prevalent epitaxy inside V-grooved pockets, our method features epitaxy inside trapezoidal troughs and thus enables the flexible integration of different III-V compounds on SOIs with different Si device layer thicknesses. Then, using InP as an example, we detailed the growth process and performed extensive study of the crystalline quality of the epitaxial III-V. Finally, we designed and fabricated both pure InP and InP/InGaAs lasers, and we achieved room-temperature lasing in both the 900 nm band and the 1500 nm band under pulsed optical excitation. Direct epitaxy of these in-plane and bufferless 1.5 µm III-V lasers on the 220 nm SOI platform suggests the imminent interfacing with Si-based photonic devices and the subsequent realization of fully integrated Si-based photonic circuits.

Synergistic effect triggers the Ostwald ripening for the downward recrystallization of perovskite to form buried submicrocavities as light output coupler.The simulation suggests the buried submicrocavities can improve the light out-coupling efficiency from 26.8% to 36.2% for near-infrared light.Light-emitting diodes yields peak external quantum efficiency increasing from 17.3% at current density of 114 mA cm−2to 25.5% at current density of 109 mA cm−2and a radiance increasing from 109 to 487 W sr−1m−2with low rolling-off.

Acrylonitriles with aggregation-induced emission (AIE) characteristics have been found to show promising applications in two-photon biomedical imaging. Generally, elaborate synthetic efforts are required to achieve different acrylonitriles with distinct functionalities. In this work, we first reported the synthesis of two different group-functionalized AIE-active acrylonitriles (TPAT-AN-XF and 2TPAT-AN) obtained simply by mixing the same reactants at different temperatures using a facile and transition metal-free synthetic method. These two AIE luminogens (AIEgens) exhibit unique properties such as bright red emission in the solid state, large Stokes shift, and large two-photon absorption cross section. Water-soluble nanoparticles (NPs) of 2TPAT-AN were prepared by a nanoprecipitation method. In vitro imaging data show that 2TPAT-AN NPs can selectively stain lysosome in live cells. Besides one-photon imaging, remarkable two-photon imaging of live tumor tissues can be achieved with high resolution and deep tissue penetration. 2TPAT-AN NPs show high biocompatibility and are successfully utilized in in vivo long-term imaging of mouse tumors with a high signal-to-noise ratio. Thus, the present work is anticipated to shed light on the preparation of a library of AIE-active functionalized acrylonitriles with intriguing properties for biomedical applications.

A compact, efficient, and monolithically grown III–V laser source provides an attractive alternative to bonding off-chip lasers for Si photonics research. Although recent demonstrations of microlasers on (001) Si wafers using thick metamorphic buffers are encouraging, scaling down the laser footprint to nanoscale and operating the nanolasers at telecom wavelengths remain significant challenges. Here, we report a monolithically integrated in-plane InP/InGaAs nanolaser array on (001) silicon-on-insulator (SOI) platforms with emission wavelengths covering the entire C band (1.55 μm). Multiple InGaAs quantum wells are embedded in high-quality InP nanoridges by selective-area growth on patterned (001) SOI. Combined with air-cladded InP/Si optical cavities, room-temperature operation at multiple telecom bands is obtained by defining different cavity lengths with lithography. The demonstration of telecom-wavelength monolithic nanolasers on (001) SOI platforms presents an important step towards fully integrated Si photonics circuits.

Multicomponent quasi-two-dimensional perovskites (Q-2DPs) have efficient luminescence and improved stability, which are highly desirable for light-emitting diode and perovskite solar cell (PSC). However, the lack of radiative recombination at room temperature is still not well understood and the performance of PSC is not good enough as well. The open-circuit voltage (VOC) is even lower than that of three-dimensional (3D) PSC with a narrower band gap. In this work, we study the energy transfer of excitons between their multiple components by time-resolved photoluminescence and find that charge transfer from high-energy states to low-energy state is gradually suppressed during elevating temperature owing to trap-mediated recombination. This may reveal the bottleneck of luminescence at room temperature in Q-2DPs, leading to large photovoltage loss in 2D PSC. Therefore, we develop a p–i–n bulk heterojunction (BHJ) structure to reduce the nonradiative recombination and obtain high VOCof 1.18 V for (PMA)2MA4Pb5I15Cl (33.3% PMA) BHJ device, much higher than that of the planar counterparts. The enhanced efficiency is attributed to the improved exciton dissociation via BHJ interface. Our results provide an important step toward high VOCand stable 2D PSCs, which could be used for tandem solar cell and colorful photovoltaic windows.

In this work, we report the application of the aggregation-induced emission luminogens (AIEgens) as color converters for visible light communication (VLC). In the form of pure solid powder, the AIEgens studied herein have demonstrated blue-to-red full-color emissions, large −6 dB electrical modulation bandwidths up to 279 MHz (∼56× that of commercial phosphor), and most of them can achieve high data rates of 428–493 Mbps (up to ∼49× that of commercial phosphor) at a maximum bit error rate of 3.8 × 10–3using on–off keying. Their data communication performances strongly suggest that AIEgens are very promising candidates as color converters for VLC applications, together with their unique AIE properties that will benefit usage in high concentration. Based on the comprehensive experimental results, we further propose some insights into improving data rate of the color converter in VLC: the data rate limit is influenced by modulation bandwidth and signal-noise ratio (SNR). We have experimentally proved that the −6 dB electrical modulation bandwidth fccan be estimated from the effective lifetime τ of the color converter with the theoretical prediction of fc=3/(2πτ)within experimental uncertainties, while theoretically derived that the SNR is proportional to its PL quantum efficiency. These observations and implications are very profound for exploring materials as color converters and improve the data transmission performance in VLC.

We demonstrate all-perovskite light-emitting diodes (PeLEDs) with white emission on the basis of simultaneously solving a couple of issues including the ion exchanges between different perovskites, solvent incompatibility in the solution process of stacking different perovskites and carrier transport layers, as well as the energy level matching between each layer in the whole device. The PeLEDs are built with a two-dimensional (CH3CH2CH2NH3)2CsPb2I7perovskite that emits red light, CsPb(Br,Cl)3quantum dots that emit a cyan color, and an interlayer composed of bis(1-phenyl-1H-benzo[d]imidazole)phenylphosphine oxide (BIPO) and poly(4-butylphenyl-diphenyl-amine) (Poly-TPD). The interlayer is designed to realize desirable white electroluminescence by tuning the electron and hole transportation and distribution in-between multilayers. With this PeLED configuration, we achieve the typical white light with chromaticity coordinates of (0.32, 0.32) in Commission Internationale de L’Eclairage (CIE) 1931 color space diagram and steady CIE coordinates in a wide range of driving current densities (from 2.94 to 59.29 mA/cm2). Consequently, our work, as the starting point for future research of all-perovskite white PeLEDs, will contribute to the future applications of PeLEDs in lighting and display. In addition, we believe that the proposed material and all-perovskite concept will leverage the design and development of more perovskite-based devices.