Enhancement-mode (E-mode) Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) grown on silicon substrates are pivotal for next-generation power electronics. However, the selective removal of the p-GaN layer in the access regions remains a critical manufacturing bottleneck. Conventional high-energy plasma etching induces severe lattice damage and generates deep-level trap states, leading to severe off-state gate leakage and threshold voltage instability. This paper investigates a low-damage, cyclic Atomic Layer Etching (ALE) process for p-GaN gate HEMTs on an silicon platform. By decoupling the etching process into a self-limiting $\mathbf{O}_{\mathbf{2}}$ plasma oxidation step and a highly selective $\mathbf{B C l}_{3}$ removal step, physical ion bombardment is virtually eliminated. The ALE process achieves a sub-nanometer surface roughness of 0.52nm, significantly restores the AlGaN surface barrier height to 0.85 eV, and suppresses the interface trap density $\left(\mathrm{D}_{\text{it }}\right)$ to $5.0 \times 10^{11} \text{cm}^{-} { }^{\mathbf{2}} \mathbf{e V}^{\mathbf{- 1}}$. Consequently, the trap-assisted tunneling (TAT) leakage pathway is effectively severed, resulting in a two-order-of-magnitude reduction in off-state gate leakage current $(\text{IG,off} \sim \mathbf{1 0}^{\mathbf{- 8}} \mathbf{A} / \mathbf{m m})$. Furthermore, the precise “stop-on-AlGaN” control preserves the two-dimensional electron gas (2DEG) mobility, ensuring a highly uniform threshold voltage $(\mathrm{V}_{\text{th }})$ distribution and low access resistance.

The incorporation of thick active layers (>300 nm) is an essential requirement for wide-scale industrial production of organic solar cells (OSCs). However, it is still challenging to achieve efficient thick film devices, in particular for all-polymer OSCs, which are generally considered the most stable type of OSCs. In this study, a simple yet effective method is introduced by using a direct current (DC) field to manipulate the morphology of bulk heterojunction (BHJ) films within all-polymer OSCs during a blade coating process. By utilizing this method, a favorable vertical phase distribution is achieved, thereby effectively reducing the electron percolation threshold and enhancing the overall device performance. With this, an outstanding efficiency of 17.59% is achieved for thick-film all-polymer devices by blade-coating, which is the best performance in this category. This study introduces a non-contact DC field method aimed at mitigating the fabrication challenges encountered when transitioning thick-film all-polymer systems from laboratory to manufacturing settings, and will potentially contributing to the advancement of the OSC industrialization.

As high-efficiency energy conversion systems, indoor organic photovoltaic (IOPV) devices exhibit exceptional suitability for powering Internet of Things (IoTs)-integrated indoor electronics, such as environmental sensors, wearable technologies, and smart home systems under ambient illumination. Advancements in materials science and device engineering have driven substantial progress in optimizing the light-harvesting capabilities, power conversion efficiencies (PCEs), and operational stability of IOPV devices in recent years. This review systematically analyzes the spectral characteristics of indoor light sources, strategies for device architecture, and photovoltaic material design tailored for low-intensity indoor environments. Furthermore, it explores emerging applications of IOPV devices in human-device interaction paradigms, focusing on two critical dimensions: user-centric ocular safety protocols and light-induced emotional regulation mechanisms. This work synthesizes current advancements in performance optimization and innovative developments, providing critical insights to enhance the efficiency and practical deployment of IOPV technologies.

Semitransparent organic photovoltaics (ST-OPVs), due to their transparency, can be integrated into building designs through building integrated photovoltaics (BIPVs) to address the energy challenges posed by urbanization. While current BIPVs such as photovoltaic windows meet the criteria for both the power supply and urban esthetics, a crucial aspect remains underexplored in the existing research: the human experience under such modulated sunlight. In this study, we conduct a systematic analysis of the interaction between spectrally tunable ST-OPV materials and human cognition and emotion, proposing a framework for selecting user-friendly ST-OPVs. Our results reveal that predominant high-performance donor polymer materials negatively influence user emotions. To address this issue, we employed spectrum shaping optical structures to optimize the device transmittance and color rendering properties, to achieve desirable human emotion feedback. This groundbreaking study delves into the user experience of ST-OPV devices, playing a crucial role in addressing the energy demands of urbanization and paving the way for the realization of smart, sustainable, and healthy cities.

The research prepared two deep ultraviolet (DUV) AlGaN-based multiple quantum well (MQW) samples with the same Al content in the QWs but different well widths (3 nm for Sample A and 2 nm for Sample B). Photoluminescence (PL) measurements reveal that Sample A exhibits only one main PL peak across all measured temperatures, while Sample B displays one main PL peak at low temperatures and two distinct PL peaks at high temperatures. Furthermore, compared with Sample A, Sample B exhibits a more significant temperature-dependent PL peak wavelength blue shift relative to the Varshni curve, a more significant excitation power density-dependent PL peak blue shift accompanied by linewidth broadening, as well as a larger non-radiative recombination related activation energy and higher internal quantum efficiency (IQE). These findings can be explained by the observation that the narrower well width of Sample B induces a more pronounced effect of carrier localization than the wider well width of Sample A, due to the enhanced fluctuation in well width and reduced quantum-confined Stark effect (QCSE).

Semitransparent organic photovoltaic (ST-OPV) cells, with their transparency and aesthetic characteristics, demonstrate tremendous application potential in the field of building integrated photovoltaics (BIPVs), such as photovoltaic windows, skylights, and photovoltaic greenhouses. Unlike traditional inorganic materials, the unique absorption characteristics of organic materials enable ST-OPV cells to selectively utilize the solar spectrum, balancing both the power conversion efficiency (PCE) and the average visible transmittance (AVT). With the rapid development of narrow bandgap acceptor materials, the PCE of ST-OPV cells has reached over 13%, and the AVT has exceeded 20%. This work reviews the latest progress of ST-OPV cells, summarizes the optimization strategies of high performance ST-OPV cells in terms of active layer engineering, electrode engineering, and device engineering. Finally, some insightful guidelines are provided for future developments in ST-OPV cells from materials, device and commercialization points.

We systematically evaluated the photobiological safety of mainstream ST-PV devices and fabricated a series of high-performance human-friendly ST-PV devices with LUE values exceeding 5.0% and low skin/eye damage levels for human beings.

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This study investigated the effect of etching process parameters on the sidewall morphology and bottom metal etching damage of Distributed Bragg Reflector (DBR), and analyzed the underlying mechanisms. By comparing the etching morphology under different RF power and pressure conditions, it was found that increasing RF power and reducing pressure can solve the problem of sidewall fracture and obtain a smooth sidewall morphology. By comparing the effect of different process gases on the sidewall angle, it was found that adding O 2 can reduce the DBR/Photoresit selectivity and sidewall angle while adding BCl 3 can increase the DBR/Photoresit selectivity and sidewall angle. Therefore, the sidewall angle can be adjusted by controlling the type and flow rate of the etching gas. By comparing the DBR/metal selectivity under different RF power, it was found that as the RF power decreases, the DBR/metal selectivity increases, which can prevent metal splashing caused by over-etching of metal. Therefore, in DBR etching, high RF power is used for main etching to obtain a smooth sidewall morphology and the sidewall angle can be adjusted by varying the gas type and flow rate, while low RF power is used for over-etching to improve the DBR/metal selectivity and prevent metal over-etching. This study has reference significance for the development of the inverted chip DBR process.

Two different InGaN/GaN multiple quantum wells (MQWs) were prepared. They contain AlN low-temperature interlayers (LTILs) between the GaN barrier and InGaN well layers, one with a trapezoidal InGaN QW and the other with a quasi-trapezoidal InGaN QW without terminal In composition gradient region (ICGR). Meanwhile, their photoluminescence (PL) spectra were acquired and their dependences on the excitation power and temperature were studied. These measurements reveal a smaller quantum-confined Stark effect, a stronger carrier localization effect, and a higher internal quantum efficiency of the quasi-trapezoidal QWs compared with that of the trapezoidal QWs. This phenomenon is a result of the fact that: the characteristic structure of the quasi-trapezoidal InGaN QWs, cannot only reduce strain in the active region due to effective strain-compensated effect of the AlN LTILs, but also avoid diffusion of In atoms from the high In region containing In-rich clusters into the terminal ICGR due to the lack of the terminal ICGRs. The former reduces the piezoelectric polarization fields induced by the lattice mismatch between well and barrier layers, the latter suppresses the degradation of the In-rich clusters and the generation of non-radiative centers.

The pursuit of high-performance low-cost organic light-emitting materials is a long-term task. The down-and upconverted fluorescence from an electron donor-acceptor host composed of di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole with fluo-rescent guests, 9,10-bis [N,N-di-(p-tolyl)-amino ] anthracene (TTPA) and 5,6,11,12-tetraphenylnaphthacene (rubrene), was investigated. We found that the energy loss mechanism can be greatly suppressed by the effective Forster resonance energy transfer process from the exciplex host to fluorescent guests. An extremely high photoluminescence quantum yield (PLQY) up to 98.41% was achieved, as well as strong upconverted green, orange, and blue fluorescence was observed in TTPA-, rubrene-, and undoped exciplex blends, respectively, under the excitation of near-infrared femtosecond laser. These low-cost materials with high PLQYs and strong upconverted fluorescence properties may have great application potential in light-emitting devices, lasers, and bioimaging applications.

The solvent-free fabrication of nonlinear optical (NLO) cocrystals is a challenge in view of the insufficient cocrystallization ability of most molecules. Here, we reported a charge-transfer (CT) cocrystal with a strong cocrystallization ability and a two-photon excited fluorescence (TPEF) property. The structural and optical properties were experimentally investigated by X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR), absorption, photoluminescence (PL), and two -photon excited fluorescence spectra. Furthermore, they were theoretically discussed by molecular electrostatic potential (MEP), Hirshfeld surface, reduced density gradient (RDG), frontier molecular orbitals (FMO), time-dependent density functional theory (TDDFT), and quadratic response calculations based on the DALTON program. Our work may be helpful for further "green" solvent-free fabrication of NLO materials.

The photoluminescence (PL) spectra of a range of InGaN/GaN multiple-quantum-well (MQW) structures dependent on temperature that have different well layer growth rates (WLGRs) were analyzed. The results show that the InGaN well layers of all structures are composed of two separate phases: In-rich clusters and an InGaN matrix. Also, with increasing WLGR, the In-rich clusters-related PL intensity increases significantly relative to its InGaN matrix-related counterpart at low temperatures, meanwhile the behavior of temperature-dependent relaxation followed by expansion of the carriers in both phases becomes less significant. These behaviors are interpreted thus: an increasing WLGR can shorten exposure of the upper layer face to the atmosphere during the growth of InGaN well layers, and this suppresses the migration of In atoms on the surface from the In-rich clusters to the surrounding InGaN matrix, thus resulting in an increasing of the density of states ratio of the In-rich clusters to the InGaN matrix and a weakening of the composition fluctuation in both phases.

Optical band gap or band gap is an important characteristic parameter of semiconductor materials. In this study, several representative InGaN/GaN multiple quantum well structures are taken as the research objects, and the test conditions that need to be met for the luminescence measurement of the optical band gap of the InGaN well layer at a certain target temperature are discussed in depth. Since the InGaN well layer is a multi-element alloy and is subjected to stress from the GaN barrier layer, there exist not only impurity/defect-related non-radiation centers in the well layer, but also localized potential fluctuation induced by composition fluctuation and quantum confinement Stark effect (QCSE) induced by polarization field. Therefore, in order to obtain a more accurate optical band gap of the InGaN well layer, we propose the following test conditions that the luminescence measurement should meet at least, that is, the influence of the non-radiation centers, the localized centers and the QCSE on the emission process at the target temperature must be eliminated. Although these test conditions need to be further improved, it is expected that this test method can provide valuable guidance or ideas for measuring the semiconductor optical band gap.

With the rise of Internet of Things, indoor organic photovoltaic (IOPV) devices as the promising power supply unit of off-grid electronics have made great progress in recent years. However, as the only acceptable end-goal, their commercial large-scale production is still a long way off although the absolute efficiency values achieve significant breakthroughs and have exceeded 30%. One of the main obstacles to practical application is the impact of IOPV devices on human vision under indoor conditions. Because the IOPV devices usually require expansive areas deployed for larger output power under indoor cases, a semitransparent strategy is commonly adopted to reduce the effects on indoor light environments. Conventional semitransparent bulk heterojunctions (BHJs) with wide-bandgap donors and near-infrared absorbing acceptors generate a huge proportion of residual blue light, which may cause human visual fatigue and injury. Herein, we propose a fullerene derivative blending strategy to suppress the blue light hazards caused by the state-of-the-art IOPV devices and improve the overall device performance. A series of high-efficient non-fullerene BHJs were selected as model systems, and a low dosage of PC71BM molecules can effectively reduce the blue light hazard efficacy (KB,v). Furthermore, with the desirable electron transport property and strong absorbance of PC71BM in the wavelength range of 400–500 nm, the ternary PM6:Y6:PC71BM devices enjoy remarkably improved power conversion efficiencies. This work provides an effective approach to simultaneously suppress KB,v values and improve performance of IOPV devices.

Photoluminescence (PL) spectra dependent on the excitation power and temperature of two different red-emitting InGaN/GaN trapezoidal multiple quantum wells (TMQWs), with GaN and AlN low-temperature interlayers (LTILs) between the InGaN well and GaN barrier layers, were investigated. It was found that compared with the TMQWs with GaN LTILs, the TMQWs with AlN LTILs have a better structural quality, more significant carrier-localizing effect, and superior internal quantum efficiency. The results can be explained by the fact that due to the stability of Al–N bond and strain-compensated effect of AlN, compared with the GaN LTIL, the AlN LTIL grown on the InGaN well layer with embedded In-rich quantum dots (QDs), cannot only reduce threading dislocation densities as confirmed by XRC measurements, but also prevent In atoms from diffusing from In-rich QDs to InGaN matrix and/or from the InGaN well to GaN barrier layer, thus suppressing degradation of the QDs and generation of non-radiative centers.

Temperature-dependent and driving current-dependent electroluminescence spectra of two different InGaN/GaN multiple quantum well structures SA and SB are investigated, with the In composition in each well layer (WL) along the growth direction progressively increasing for SA and progressively decreasing for SB. The results show that SB exhibits an improved efficiency droop compared with SA. This phenomenon can be explained as follows: owing to the difference in growth pattern of the WL between these two samples, the terminal region of the WL in SB contains fewer In atoms than in SA, and therefore the former undergoes less In volatilization than the latter during the waiting period required for warming-up due to the difference in the growth temperature between well and barrier layers. This results in SB having a deeper triangular-shaped potential well in its WL than SA, which strongly confines the carriers to the initial region of the WL to prevent them from leaking to the p-GaN side, thus improving the efficiency droop. Moreover, the improvement in the efficiency droop for SB is also partly attributed to its stronger Coulomb screening effect and carrier localization effect.

Two multiple quantum well (MQW) InGaN/GaN structures emitting green light, without (A) and with (B) an indium (In) volatilization suppression technique (IVST) during growth of the active region, were fabricated. The dependencies of the photoluminescence (PL) spectra upon temperature at different levels of excitation power were investigated. The results indicate that an IVST can increase the In content while suppressing the phase separation caused by volatilization of that In incorporated in the well layers. Also, compared with Structure B with IVST, which contains one phase structure, Structure A without IVST, which contains two separate phases (i.e., an In-rich phase and an In-poor phase), exhibits higher internal quantum efficiency (IQE) at low excitation power and lower IQE at high excitation power. The former is mainly attributed to the stronger In-rich phase-related localization effect of Structure A, because the In-rich phase-related emission dominates the PL spectra of Structure A at a low excitation power; the latter is mainly due to the In-poor phase-related weaker localization effect of Structure A, because the In-poor phase-related emission dominates the PL spectra of Structure A at high excitation power because localized states in this In-rich phase are saturated.

Two light-emitting diodes (LEDs) enabled by InGaN/GaN multiple quantum wells (MQWs) with different well layer growth temperatures (WLGTs) were prepared. The dependences of electroluminescence (EL) spectra of these two structures on temperature at various fixed injection currents indicate that, a decreasing WLGT can result in a conversion of the well layer structure from a one-zone structure with better homogeneity in the localization depth into a two-zone structure with different average In contents and different localization depths, due to the increased In content-induced enhanced component fluctuation. The former is inferred from an "inverted-V-shaped" (increasing-decreasing) temperature-dependent behavior of peak energy at all fixed currents; the latter is mainly inferred from an "M-shaped" (increasing-decreasing-increasing-decreasing) temperature-dependent behavior of peak energy at intermediate fixed currents. These explanations also match those given for temperature-dependent behaviors in terms of external quantum efficiency (EQE) of these two LEDs, including "M-shaped" temperature-dependent behaviors of the EQE of LED B at the intermediate fixed currents.