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Hexagonal boron nitride (h-BN) epilayers have been recognized as a promising material for applications in solid-state neutron detectors. However, the highest detection efficiency of 58% attained so far for 1 mm2 detectors fabricated from 50 μm thick B-10 enriched h-BN films still falls short of the expected theoretical value of 64%. This is due to the less than perfect charge collection efficiency. In this work, we have fabricated and analyzed the photocurrent-voltage characteristics of 11 h-BN neutron detectors. The dependence of the charge collection efficiency (ηc) on the charge carrier mobility-lifetime (μτ) product of the bulk trapping parameter reveals that ηc is nearly perfect at a bias voltage of 200 V if we neglect the effects of surface recombination. Our results have clearly demonstrated that the surface recombination of charge carriers is the dominant factor that prevents a further enhancement in the charge collection efficiency in our current detectors. The surface recombination field ES (=s/μ), defined as the ratio of the surface recombination velocity (s) to the carrier mobility (μ) of holes, was found to have a linear relationship with that of electrons and has a magnitude of the order of 104 V/cm. The present study indicates that it is critical to reduce ES in h-BN in order to further push the charge collection and hence the total detection efficiency of h-BN neutron detectors to 100%. [ABSTRACT FROM AUTHOR]

As thin-film and silicon solar technologies mature, questions emerge about the upper bounds of thin-film solar performance and realistic experimental paths to reach them. Directions include increasing absorber hole density and bulk lifetime, improving the junction interface, reducing back-surface recombination, and implementing a back-surface electron reflector. Textbook solutions of idealized p-n junctions create a powerful conceptualization of solar cells as predominantly minority-carrier-driven devices. We demonstrate that thin films are distinct, and models often fail to capture the important role of majority-carrier lifetime, leading to contradictions with lifetime measurements and overestimates of potential device improvement from back-surface passivation and/or reflectors. Furthermore, we identify methods to probe majority-carrier lifetime and re-examine the degree to which back-surface passivation and electron reflectors can increase efficiency for a range of common thin-film interface and absorber properties, using current and emerging CdTe technology as an example. Results indicate that a practical approach is to focus first on improving front-interface recombination velocity and the absorber properties, and then on implementing the back-surface passivation or reflector, which can ultimately allow thin-film solar technology to reach 28% efficiency. [ABSTRACT FROM AUTHOR]

Abstract Silica‐aluminium composite powders are important precursors for the preparation of sealant coatings by supersonic flame spraying. Micron‐scale silica‐aluminium composite powders can be prepared using a planetary ball mill, but powder agglomeration often leads to composite failure. Using relevant modelling software to build the 3D modelling of the ball mill jar, which based on the discrete element method, using the Hertz–Mindlin contact model and after specifying the simulation boundary conditions, the ball mill process was simulated and analysed. Visualise the influence of important process parameters such as frequency, size and diameter of milling balls and ball‐to‐powder weight ratio, and systematically analyse the microscopic morphology and composite condition of the agglomerated and dispersed powders. The results show that the ball motion during the ball milling process is mainly divided into three representative types: ball–ball impact, ball crushing motion against the jar wall and ball–wall impact. The energy transfer efficiency of the milling balls to the powder system is highest when the ratio of the three types of motion is uniform. SEM images and EDS spectra showed that the aluminium powder was sufficiently crushed, with an average particle size below 1 μm. The aluminium powder was uniformly distributed on the surface of the silicon powder, and the particle size of the composite silicon aggregates was sufficiently reduced.

Abstract Oxide‐based photoelectrodes commonly generate deep trap states associated with various intrinsic defects such as vacancies, antisites, and dislocations, limiting their photoelectrochemical properties. Herein, it is reported that rhombohedral GaFeO3 (GFO) thin‐film photoanodes exhibit defect‐inactive features, which manifest themselves by negligible trap‐states‐associated charge recombination losses during photoelectrochemical water splitting. Unlike conventional defect‐tolerant semiconductors, the origin of the defect‐inactivity in GFO is the strongly preferred antisite formation, suppressing the generation of other defects that act as deep traps. In addition, defect‐inactive GFO films possess really appropriate oxygen vacancy concentration for the oxygen evolution reaction (OER). As a result, the as‐prepared GFO films achieve the surface charge transfer efficiency (ηsurface) of 95.1% for photoelectrochemical water splitting at 1.23 V versus RHE without any further modification, which is the highest ηsurface reported of any pristine inorganic photoanodes. The onset potential toward the OER remarkably coincides with the flat band potential of 0.43 V versus RHE. This work not only demonstrates a new benchmark for the surface charge transfer yields of pristine metal oxides for solar water splitting but also enriches the arguments for defect tolerance and highlights the importance of rational tuning of oxygen vacancies.

Inserting an ultrathin low-conductivity interlayer between the absorber and transport layer has emerged as an important strategy for reducing surface recombination in the best perovskite solar cells. However, a challenge with this approach is a trade-off between the open-circuit voltage (Voc) and the fill factor (FF). Here, we overcame this challenge by introducing a thick (about 100 nanometers) insulator layer with random nanoscale openings. We performed drift-diffusion simulations for cells with this porous insulator contact (PIC) and realized it using a solution process by controlling the growth mode of alumina nanoplates. Leveraging a PIC with an approximately 25% reduced contact area, we achieved an efficiency of up to 25.5% (certified steady-state efficiency 24.7%) in p-i-n devices. The product of Voc × FF was 87.9% of the Shockley-Queisser limit. The surface recombination velocity at the p-type contact was reduced from 64.2 to 9.2 centimeters per second. The bulk recombination lifetime was increased from 1.2 to 6.0 microseconds because of improvements in the perovskite crystallinity. The improved wettability of the perovskite precursor solution allowed us to demonstrate a 23.3% efficient 1-square-centimeter p-i-n cell. We demonstrate here its broad applicability for different p-type contacts and perovskite compositions. [ABSTRACT FROM AUTHOR]

Solar‐driven photoelectrochemical (PEC) hydrogen production is one potential pathway to establish a carbon‐neutral society. Nowadays, quantum dots (QDs)‐sensitized semiconductors have emerged as promising materials for PEC hydrogen production due to their tunable bandgap by size or morphology control, displaying excellent optical and electrical properties. Nevertheless, they still suffer from anodic corrosion during long‐term cycling, offering poor stability. This Review discussed advancements to improve long‐term stability of QDs particularly in terms of cocatalysts and passivation layers. The working principle of PEC cells was reviewed, along with all important configurations adopted over recent years. The equations to assess PEC performance were also described. A greater emphasized was placed on QDs and incorporation of cocatalysts or passivation layers that could enhance the PEC performance by influencing the charge transfer and surface recombination processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of BiPS 4 -Bi 2 S 3 /BiVO 4 photoanodes via photoelectrochemcial transfromation process. • Synergistic effect of BiPS 4 -Bi 2 S 3 co-catalytic layer over BiVO 4 electrodes with enriched PEC performances. • A photocurrent of 3.7 mA/cm2 with nearly 6-fold enhancement is achieved. Bismuth vanadate (BiVO 4) is the most favorable electrode candidate for photoelectrochemical (PEC) water-splitting reactions. The poor charge separation and sluggish water oxidation dynamics are, however, the major setbacks of BiVO 4 photoanodes. To address these issues, we demonstrate that bismuth thiophosphate (BiPS 4)-Bi 2 S 3 hybrid nanostructure was photoelectrochemically transformed on BiVO 4 electrodes (BiPS 4 -Bi 2 S 3 -Bi 2 O 3) when treated in Na 2 S/PBS electrolyte, and a notable photocurrent of 3.5 mA/cm2 at 0.65 V RHE was obtained showing promising stability. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) examination evidenced the effective makeover of BiVO 4 into the BiPS 4 -Bi 2 S 3 /BiVO 4 nanostructured matrix. A negatively shifted onset potential and enriched durability are achieved for heterostructured BiPS 4 -Bi 2 S 3 /BiVO 4 photoanodes due to decreased surface recombination. Interestingly, the Bode phase analysis evidenced the faster hole consumption in the water oxidation process in the BiPS 4 -Bi 2 S 3 /BiVO 4 electrode compared to pristine BiVO 4. This methodology can be engaged to design different complex nanostructured materials with tunable optical and electrical features for photoelectrocatalysis, electrical energy storage, and solar cell uses. [ABSTRACT FROM AUTHOR]

Investigation of surface recombination is an important area for infrared detectors as the demand for smaller pixels increases. In this study, we use transient microwave reflectance to characterize the minority carrier lifetime of InAsSb nBn structures under three conditions: As-Grown, blanket Barrier-Etched, and SU-8 Passivated blanket barrier-etched. A qualitative comparison of these three samples shows that the minority carrier lifetime decreases for the Barrier-Etched sample compared to the As-Grown sample, indicating that the minority carrier lifetime is sensitive to changes in the sample surface, specifically the introduction of surface states. We compare these samples quantitatively using a polynomial fit (A−1 + Bn + Cn2). We find for the As-Grown sample A = 1.22 ± 0.45 µs, B = 2.5 ± 0.2 × 10−12 cm3/s, and C = 5.004 ± 4.996 × 10−31 cm6/s, for the Barrier-Etched sample A = 1.17 ± 0.40 µs, B = 9.9 ± 0.2 × 10−12 cm3/s, and C = 9.502 ± 9.498 × 10−30 cm6/s, and for the Passivated sample A = 1.34 ± 0.45 µs, B = 5.3 ± 0.5 × 10−12 cm3/s, and C = 5.500 ± 4.500 × 10−33 cm6/s. [ABSTRACT FROM AUTHOR]

Many kinds of defects are present in AlGaN/GaN-on-Si based power electronics devices. Their identification is the first step to understand and improve device performance. Electron traps are investigated in AlGaN/GaN-on-Si power diodes using deep level transient Fourier spectroscopy (DLTFS) at different bias conditions for two Schottky contact's etching recipes. This study reveals seven different traps corresponding to point defects. Their energy level ET ranged from 0.4 eV to 0.57 eV below the conduction band. Among them, two new traps are reported and are etching-related: D3 (ET = 0.47–0.48 eV; σ ≈ 10−15 cm2) and D7 (ET = 0.57 eV; σ = 4.45 × 10−12 cm2). The possible origin of the other traps are discussed with respect to the GaN literature. They are proposed to be related to carbon and nitrogen vacancies or to carbon, such as CN-CGa. Some others are likely due to crystal surface recombination, native defects or a related complex, or to the nitrogen antisite: NGa. [ABSTRACT FROM AUTHOR]

Germanium (Ge) has attracted much attention as a promising channel material in nanoscale metal–oxide–semiconductor devices and near‐infrared sensing because of its high carrier mobilities and narrow bandgap, respectively. However, efficient passivation of Ge surfaces has remained challenging. Herein, silicon nitride (SiNx)‐based passivation schemes on Ge surfaces are studied and the observations are compared to Si counterparts. These results show that instead of a high positive charge density (Qtot) that is found in SiNx‐passivated Si samples, similar Ge samples contain a high amount of negative Qtot (in the range of 1012 cm−2). The maximum surface recombination velocity of the samples is shown to reduce by a factor of three in both Si and Ge samples by a post‐deposition anneal at 400 °C. The SiNx‐coated samples are capped with an atomic‐layer‐deposited aluminum oxide (Al2O3) layer, which reduces the midgap interface defect density (Dit) after annealing to 7 × 1010 and 4 × 1011 cm−2 eV−1 in Si and Ge, respectively. Interestingly, while the Al2O3 capping seems to have no impact on Qtot of the Si samples, it turns the stack virtually neutral (∼−1.6 × 1011 cm−2) on Ge. The presented SiNx‐based passivation schemes are promising for optoelectronic devices, where a low Dit and/or a low charge are favored. [ABSTRACT FROM AUTHOR]

CoOOH nanodots decorated hematite (CoOOH/Fe 2 O 3) photoanode was successfully fabricated. The CoOOH/Fe 2 O 3 exhibits a high photocurrent density of 1.92 mA cm−2 at 1.23 V vs. RHE, which is ca. 2.6 times to that of bare Fe 2 O 3 , and a ca. 110 mV cathodic shift of the onset potential. CoOOH plays important roles that suppress the surface recombination and improve the charge transfer. [Display omitted] • CoOOH nanodot was rationally designed and in-situ decorated on Fe 2 O 3 photoanode. • CoOOH/Fe 2 O 3 exhibited superior photoelectrochemical activity for water oxidation. • CoOOH could suppress charge recombination by passivating the surface states of Fe 2 O 3. • CoOOH provided active sites and facilitated the charge transfer for water oxidation. Photoelectrochemical (PEC) water splitting has been considered as an alternative process to produce green hydrogen. However, the energy conversion efficiency of PEC systems was still limited by the inefficient photoanode. Cocatalysts decoration is regarded as an efficient strategy for improving PEC performance of photoanode. In this work, nanodot-like cobalt (oxy)hydroxides was rationally decorated on hematite to fabricate CoOOH/Fe 2 O 3 photoanode. The resulted CoOOH/Fe 2 O 3 exhibits a high photocurrent density of 1.92 mA cm−2 at 1.23 V vs. RHE, which is 2.6 times than that of bare Fe 2 O 3. In addition, the onset potential displays a cathodic shift of ca. 110 mV, indicating that CoOOH can efficiently accelerate water oxidation kinetics over Fe 2 O 3. The comprehensive PEC and electrochemical characterizations reveal that CoOOH could not only provide abundant accessible Co active sites for water oxidation, but also could passivate the surface states of Fe 2 O 3 , thus increase the carrier density and decrease the interfacial resistance. As a result, the PEC water oxidation performance over Fe 2 O 3 was significantly boosted. This work supports that the roles of CoOOH cocatalyst is generic and such CoOOH could be used for other semiconductor-based photoanodes for outstanding PEC water splitting performance. [ABSTRACT FROM AUTHOR]

Severe surface photocarrier recombination and poor electronic conductivity are the major factors behind the sluggish photoelectrochemical water oxidation kinetics of the ZnFe2O4 photoanode. Here, the CeOx catalyst overlayer has been coupled with the reduced ZnFe2O4 nanorods (NRs) to reduce the surface charge recombination on the photoanode significantly. The density functional theory (DFT) studies indicate that the oxygen vacancy defect‐rich CeOx catalyst constructs a favorable band alignment with ZnFe2O4 promoting rapid photocarrier separation and serves as a conducting photocarrier transfer pathway accelerating the hole transportation toward the electrode/electrolyte interface. The ZnFe2O4/CeOx nano‐heterostructure photoanode exhibits a current density of 0.64 mA cm−2 at 1.23 V versus RHE under AM 1.5 G illumination, which corresponds to >167% increase over that of the ZnFe2O4 NRs photoanode. The CeOx coupling reduces the onset potential cathodically by 180 mV over the ZnFe2O4 NRs photoanode. The ZnFe2O4/CeOx nano‐heterostructure photoanode also exhibits excellent charge transfer efficiency (≈64% at 1.23 V vs RHE) and photostability. The results indicate the superior catalytic performance of oxygen vacancy defect‐rich CeOx in the PEC process. This work demonstrates the multifunctional role of CeOx as a surface passivation overlayer, hole transfer layer, and efficient oxygen evolution reaction catalyst. [ABSTRACT FROM AUTHOR]

Carbon-protected BiVO4 photoanode and Cu2O photocathode tandem photoelectrochemical (PEC) system has been explored to reduce surface recombination and enhance the stability of the photoelectrodes. In addition to the carbon layer, the electrodeposited FeOOH nanolayer and drop-casted MoS2 co-catalyst layer on the photoanode and photocathode, respectively improve the reaction kinetics. The optimized photoanode (Mo-BiVO4/C/FeOOH) and photocathode (Cu2O/C/MoS2) produces current densities of ~1.22 mA cm−2 at 1.23 V vs. RHE and ~−1.48 mA cm−2 at 0 V vs. RHE, respectively. The obtained photocurrent is higher than bare photoelectrodes without a carbon layer. Finally, a tandem cell has been constructed, and an unassisted current density of ~0.107 mA cm−2 is obtained for a carbon-protected BiVO4–Cu2O tandem PEC cell at zero bias. The improved stability and enhanced photocurrent of the carbon protective layer are attributed to its better charge transfer resistance and minimized surface defects. Carbon protective layer can be a viable option to improve the stability of photoelectrodes in aqueous media. [ABSTRACT FROM AUTHOR]

Light‐trapping elements play an important role in solar cells to enhance their light‐harvesting efficiency. Pyramidal‐shaped nano‐microstructures and gradient metasurfaces are mostly used as light‐trapping elements in solar cells. There is, however, one major concern with nanostructured solar cells: a larger surface area resulting in a larger surface recombination loss. In this article, a novel thin‐film wedge tandem‐solar cell made of perovskites and silicon is designed where the bottom cell itself works as a light‐trapping element. Optical and electrical simulations are performed to estimate performance metrics of the wedge tandem‐solar cell and compare with typically used unpatterned planar tandem‐solar cell. In terms of optical and electrical performance, wedge geometry outperforms planar geometry and shows 17.18% higher efficiency. Compared to a typical planar tandem cell, such a design can lead to thin and low‐weight tandem solar cells, which can be very useful in space applications. The proposed design can be fabricated using an optimized electrospray deposition process. [ABSTRACT FROM AUTHOR]

Incorporating localized surface plasmon resonance (LSPR) into organic solar cells (OSCs) is a popular method for improving the power conversion efficiency (PCE) by introducing better light absorption. In this work, we designed a one-pot synthesis of Ag@SiO2@AuNPs dual plasmons and observed an immense increase in light absorption over a wide range of wavelengths. Ag@SiO2 plays the main role in enhancing light absorption near the ultraviolet band. The silica shell can also further enhance the LSP resonance effect and prevent recombination on the surface of AgNPs. The AuNPs on the Ag@SiO2 shell exhibited strong broad visible-light absorption due to LSP resonance and decreased light reflectance. By utilizing Ag@SiO2@AuNPs, we could enhance the light absorption and photoinduced charge generation, thereby increasing the device PCE to 8.57% and Jsc to 17.67 mA cm−2, which can be attributed to the enhanced optical properties. Meanwhile, devices without LSPR nanoparticles and Ag@SiO2 LSPR only showed PCEs of 7.36% and 8.18%, respectively. [ABSTRACT FROM AUTHOR]

Cs2AgBiBr6 is an encouraging example of perovskites which shows potential toward the development of more stable and nontoxic photoactive materials. However, relative to its necessarily large optical thickness, the material has substantially deficient electron diffusion lengths, which limit its photovoltaic efficiency. Herein, this problem is solved by designing a double‐sided semitransparent architecture for a Cs2AgBiBr6‐based photovoltaic material. In this case, the bifacial design deliberately creates an imbalance between the electron and hole densities, resulting in asymmetric lengths of carrier conduction near their respective transporting layers. Coupled optoelectronic simulations suggest that the use of the bifacial architecture results in an improvement of around 34% in the efficiency, from 3.47% to 4.64%, compared to the standard configuration. This method is effective to improve electron conduction in Cs2AgBiBr6, which is typically severe compared to its hole conduction. Finally, the strength of the correlation between the power conversion efficiency of the bifacial architecture and the diffusion length, asymmetric ratio of electron and hole conduction, and light albedo factor are explored. The results highlight some ways to improve the photovoltaic efficiency of Cs2AgBiBr6 above 8%, for instance, through tuning the surface recombination and band alignment between Cs2AgBiBr6 and the hole‐transporting layer. [ABSTRACT FROM AUTHOR]

Successful manipulation of halide perovskite surfaces is typically achieved via the interactions between modulators and perovskites. Herein, it is demonstrated that a strong‐interaction surface modulator is beneficial to reduce interfacial recombination losses in inverted (p‐i‐n) perovskite solar cells (IPSCs). Two organic ammonium salts are investigated, consisting of 4‐hydroxyphenethylammonium iodide and 2‐thiopheneethylammonium iodide (2‐TEAI). Without thermal annealing, these two modulators can recover the photoluminescence quantum yield of the neat perovskite film in contact with fullerene electron transport layer (ETL). Compared to the hydroxyl‐functionalized phenethylammonium moiety, the thienylammonium facilitates the formation of a quasi‐2D structure onto the perovskite. Density functional theory and quasi‐Fermi level splitting calculations reveal that the 2‐TEAI has a stronger interaction with the perovskite surface, contributing to more suppressed non‐radiative recombination at the perovskite/ETL interface and improved open‐circuit voltage (VOC) of the fabricated IPSCs. As a result, the VOC increases from 1.11 to 1.20 V (based on a perovskite bandgap of 1.63 eV), yielding a power conversion efficiency (PCE) from ≈20% to 21.9% (stabilized PCE of 21.3%, the highest reported PCEs for IPSCs employing poly[N,N′′‐bis(4‐butylphenyl)‐N,N′′‐bis(phenyl)benzidine] as the hole transport layer, alongside the enhanced operational and shelf‐life stability for unencapsulated devices. [ABSTRACT FROM AUTHOR]

As a promising material for photoelectrochemical (PEC) water oxidation, the fast recombination rate and sluggish surface reaction for BiFeO 3 (BFO) still hinder its practical application. In this work, nitrogen plasma was first used to engineer surface defects of the pulsed laser deposition (PLD)-fabricated BFO films to suppress the surface charge recombination and improve the surface water oxidation activity, as well as enhance the stability. A remarkable photocatalytic activity enhancement was observed after the surface modification. Specifically, the photocurrent density is 95 μA/cm2 at 0.6 V (vs. Ag/AgCl, pH=12.8) for BFO–N (after nitrogen plasma treatment), which is about 8 times higher than as-grown BFO (12 μA/cm2) at the same potential. Meanwhile, the onset potential of BFO–N shifts toward the negative value by 120 mV compared to BFO. Also, the BFO–N reveals superior stability to BFO, which shows nearly no decay after the 1-h test. Complete experimental characterization and deep mechanistic analysis indicate that the enhanced performance could be due to the newly-formed Fe-enriched oxynitride layer on the surface after nitrogen plasma treatment, which suppresses the fast recombination, improves the water oxidation reaction kinetics, and protects the photoanode against photocorrosion. Our work offers a simple, but effective way to improve the PEC performance of BFO, which is instructive for fabricating similar high-performance photoelectrodes for PEC applications. [ABSTRACT FROM AUTHOR]

Herein, a monolithic micro-pixelated light-emitting diode (μLED) display realized using ion-surface-treatment-based planar-geometry pixelation is reported. A high-resolution blue-emitting μLED array is fabricated by optimizing ion species of a near-surface selectively positioned isolation process. The μLED array exhibiting inhibited surface recombination and higher output power is achieved by using heavy ions, such as fluorine (F−), due to more stable opto-electrical isolation and better process reliability. Furthermore, the low forward voltage of F−-IST-based μLED pixels can effectively improve the wall-plug efficiency for the μLED array with a pixel diameter of 6 μm. Conversely, the poor thermal stability of light hydrogen (H+) ions limits its device applications. Analysis based on a rate equation model reveals that the luminescence mechanism of F−-IST-based μLEDs is dominated by radiative recombination, which will benefit the planar-geometry pixelation for realizing highly efficient full-color microdisplays. [ABSTRACT FROM AUTHOR]

The bare surface of BiVO4 photoanode usually suffers from extremely low interfacial charge transfer efficiency which leads to a significantly suppressed photoelectrochemical water splitting performance. Various strategies, including surface modification and the loading of co-catalysts, facilitate the interface charge transfer process in BiVO4. In this study, we demonstrate that CoS2 synthesized from the hydrothermal method can be used as a high-efficient co-catalyst to sufficiently improve the interface charge transfer efficiency in BiVO4. The photoelectrochemical water splitting performance of BiVO4 was significantly improved after CoS2 surface modification. The BiVO4/CoS2 photoanode achieved an excellent photocurrent density of 5.2 mA/cm2 at 1.23 V versus RHE under AM 1.5 G illumination, corresponding to a 3.7 times enhancement in photocurrent compared with bare BiVO4. The onset potential of the BiVO4/CoS2 photoanode was also negatively shifted by 210 mV. The followed systematic combined optical and electrochemical characterization results reveal that the interfacial charge transfer efficiency of BiVO4 was largely improved from less than 20% to more than 70% due tor CoS2 surface modification. The further surface carrier dynamics study performed using an intensity modulated photocurrent spectroscopy displayed a 6–10 times suppression in surface recombination rate constants for CoS2 modified BiVO4, which suggests that the key reason for the improved interfacial charge transfer efficiency possibly originates from the passivated surface states due to the coating of CoS2. [ABSTRACT FROM AUTHOR]

The cadmium tungstate rods have been given much attention due to their potential for usage in numerous luminescent applications. We have prepared single crystalline Sn-doped Cd1−xSnxWO4 (where x = 0, 1, 3, and 5%) nanorods (NRDs) and characterized them using refined X-ray diffraction and TEM analysis, revealing a monoclinic phase and a crystallite size that decreased from 62 to 38 nm as Sn concentration increased. Precise Sn doping modulation in CdWO4 NRDs causes surface recombination of electrons and holes, which causes the PL intensity to decrease as the Sn content rises. The chromaticity diagram shows that an increase in the Sn content caused a change in the emission color from sky blue to light green, which was attributed to the increased defect density. The photoluminescence time decay curve of all samples fit well with double-order exponential decay, and the average decay lifetime was found to be 1.11, 0.93, and 1.16 ns for Cd1−xSnxWO4, x = 0, 1, and 5%, respectively. This work provides an understanding of the behavior of Sn-doped CdWO4 NRDs during electron transitions and the physical nature of emission that could be used in bio-imaging, light sources, displays, and other applications. [ABSTRACT FROM AUTHOR]

The development of efficient multifunctional catalyst remains a huge challenge due to their unsatisfactory oxygen/hydrogen intermediate species adsorption, ineffective kinetics rate, lack of active reaction sites. Herein, rich-Mo edge active sites in the molybdenum carbide (Mo 2 C) were created through nitrogen doping, which was used as cocatalyst to enhance the hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and photocatalytic hydrogen evolution (PHE) of ZnIn 2 S 4 (ZIS). Mo 2 C-N/ZIS affords a remarkable HER activity with a low overpotential of 74 mV as well as excellent OER activity with a reduced overpotential of 250 mV at 10 mA·cm−2. The formed Schottky junction between Mo 2 C-N/ZIS are responsible for the enhanced PHE/HER/OER activity, which owns double transfer route beneficial to enhancing separation of photogenerated carriers and reducing bulk/surface recombination of ZIS. Specially, the density functional theory (DFT) calculations demonstrate that Mo 2 C-N/ZIS Schottky junction with optimal absorption energy for the hydrogen and oxygen intermediates. [Display omitted] • Mo 2 C-N/ZIS Schottky junction was successfully established. • Mo 2 C-N/ZIS with optimal absorption energy for the reaction intermediates. • The H 2 evolution rate of Mo 2 C-N/ZIS Schottky junction reached 6.71 mmol g−1·h−1. • Mo 2 C-N/ZIS exhibits excellent electrocatalytic activity for HER/OER. • Mechanism of catalytic activity in Mo 2 C-N/ZIS system was proposed. [ABSTRACT FROM AUTHOR]

InGaN-based red-emitting LEDs based on V-pits exhibit patchy electroluminescence. The V-pits in the active regions can effectively capture carriers, preventing them from migrating to the chip edges. This leads to not only very weak surface recombination effect on these devices, but also strong anti-correlation between the emission wavelength and intensity due to the reduced carrier densities in the V-pit-rich regions. [Display omitted] • Different sized InGaN red LEDs (from 500 × 500 to 15 × 15 µm2) based on V-pits were characterized systematically. • Suppressed surface recombination effect is revealed, in the light–current-voltage (LIV) measurement and electroluminescence (EL) image analysis. • The analysis on the spatially-resolved EL images show that there is a strong correlation between the wavelength and the intensity, showing that the regions with longer wavelengths have weaker intensities. • This anti-correlation can be explained by the reduced carrier injection to the flat QWs in the V-pit-rich regions due to the carrier trapping by the V-pit QWs and dislocations. InGaN-based red light-emitting diodes (LEDs) are a promising candidate to achieve high efficiency, which is highly desired by the display market. Understanding their size-dependent properties is crucial for further performance improvement. In this work, different sized InGaN red LEDs (from 500 × 500 to 15 × 15 µm2) based on V-pits were characterized systematically. The current–voltage characteristics show that the leakage current density, revealed either in forward or reverse bias, is independent of the chip size. Further light output power measurements and current dependent electroluminescence also reveal very weak dependence of the power density on chip size showing insensitivity the chip perimeter. The suppressed surface recombination effect may be due to effective carrier trapping effect by the V-pits, which prevents the carriers from flowing to the sidewalls. By detailed analysis of the spatially resolved electroluminescence, an anti-correlation between the emission wavelengths and the intensities was observed, with the longer wavelength emitting regions exhibit weaker intensity, which can be explained by the reduced carrier density in the V-pit-rich regions as carriers are partially captured by quantum wells associated with the V-pits and the associated dislocations. This study will pave the way for further understanding and improving the efficiency of InGaN red LEDs including micro-LEDs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bidentate chelators enhance binding at perovskite surface defects, raising defect formation energy and curbing non-radiative recombination. • π-conjugated chelator layer aligned on the perovskite surface regulates energy levels and facilitate charge extraction. • A power conversion efficiency of 24.09% was achieved by incorporating the bidentate chelation mechanism. • Maintains over 80 % efficiency after 1000 h at 65 ± 5 % humidity due to significantly improved hydrophobicity. Surface defects seriously damage carrier transport by forming non-radiative recombination centers on the perovskite film, which negatively affect the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Here we present a strong chelate coordination bond to anchor the surface of the perovskite film. Employing Bathophenanthroline (BPhen) as a π-conjugated bidentate chelator, the uncoordinated Pb2+ can be firmly anchored accompanying with the reduced surface recombination sites, giving rise to suppressed non-radiative recombination and enhanced charge carrier extraction. With the BPhen, the perovskite film shows an approximately threefold longer carrier lifetime than the control device, leading to a champion PCE of 24.09 % and a high stable performance with retained over 80 % of its initial efficiency after 1000 h exposed to relative humidity (RH) of 65 ± 5 %. [ABSTRACT FROM AUTHOR]

Cuprous oxide layers were obtained on a conductive glass substrate via room-temperature electrochemical deposition from the electrolyte containing 0.4 M CuSO 4 , 3 M lactic acid (pH = 12) at −0.5 V vs. SCE for various durations (from 0.25 to 3 h). Physicochemical properties of as-received FTO/Cu 2 O materials were characterized using SEM, PXRD, and UV–Vis DRS. The photoelectrochemical (PEC) properties of the obtained electrodes were evaluated in detail by analyzing the influence of the energy of monochromatic radiation, and the applied polarization on the resulting photocurrent transients. It was found that Cu 2 O crystals are getting bigger and sharper with prolonged electrosynthesis duration and a slight decrease in the band gap energy from 2.4 to 2.1 eV with increasing deposition duration was observed. Moreover, this trend was also reflected in PEC properties of resulted material, higher photocurrents were generated by the material deposited for 3 h. More importantly, this PEC response was enhanced by low-temperature (100 °C, 200 °C) annealing. Thermal treatment at 100 °C led to a noticeable improvement in the photoactivity of the samples. Further increasing post-treatment temperature to 200 °C resulted in a further six-fold increase in photocurrents. Finally, the calculated values of accumulated and dissipated charges indicated significantly lower surface recombination after thermal treatment. [Display omitted] • Room-temperature electrodeposition of Cu 2 O on FTO-coated glass was studied. • The effect of synthesis time on morphology and structure was studied. • Extended deposition improves the photocurrent generated by the Cu 2 O/FTO electrodes. • Low-temperature annealing improves the PEC properties of the obtained materials. • Significantly lower surface recombination was observed after thermal treatment. [ABSTRACT FROM AUTHOR]

We determine the grain-boundary (GB) recombination velocity, S G B , and grain-interior (GI) lifetime, τ G I , parameters in superstrate CdS/CdTe thin-film solar cell technology by combining cathodoluminescence (CL) spectrum imaging and time-resolved photoluminescence (TRPL) measurements. We consider critical device formation stages, including after CdTe deposition, CdCl2 treatment, and Cu diffusion. CL image analysis methods extract GB and GI intensities and grain size for hundreds of grains per sample. Concurrently, a three-dimensional CL model is developed to simulate the GI intensity as a function of τ G I , S G B , grain size, and the surface recombination velocity, S surf . TRPL measurements provide an estimate of S surf for the CL model. A fit of GI intensity vs. grain size data with the CL model gives a self-consistent and representative set of S G B and τ G I values for the samples: S G B (τ G I) = 2.6 × 106 cm/s (68–250 ps), S G B (τ G I) = 4.1 × 105 cm/s (1.5–3.3 ns), and S G B (τ G I) = 5.5 × 105 cm/s (1.0–3.8 ns) for as-deposited, CdCl2-treated, and CdCl2- and Cu-treated samples, respectively. Thus, we find that the CdCl2 treatment both helps to passivate GBs and significantly increase the GI lifetime. Subsequent Cu diffusion increases GB recombination slightly and has nuanced effects on the GI lifetime. Finally, as a partial check on the S G B and τ G I values, they are input to a Sentaurus device model, and the simulated performance is compared to the measured performance. The methodology developed here can be applied broadly to CdTe and CdSeTe thin-film technology and to other thin-film solar cell materials including Cu(In1-xGax)Se2, Cu2ZnSnS4, and perovskites. [ABSTRACT FROM AUTHOR]

The electron beam induced current (EBIC) mode of a scanning electron microscope (SEM) is a widely used technique for the quantitative assessment of minority carrier diffusion length and surface recombination. Point source (one-dimensional) and extended source (two-dimensional) analytical models are two widely used approaches to assess this information in geometry where the electron beam (e-beam) is parallel to the p-n junction. In this article, a two-dimensional (2D) analytical model is evaluated and compared with 2D finite element numerical simulations, where the electron beam-solid interaction is modeled using a Monte Carlo simulation coupled with a drift-diffusion solver. The simulations are computed for both low and high level injection conditions. The effect of an e-beam injection level on the shape of EBIC profiles is analyzed to evaluate limitations of the analytical models. [ABSTRACT FROM AUTHOR]

Nanowires intrinsically exhibit a large surface area, which makes them sensitive to physical and chemical interactions with their environment. Here, we investigate the surface recombination at m-plane side walls of selective area-grown GaN nanowires on Si (111) subjected to different environmental conditions. In contrast to the stable photoluminescence observed from c-plane surfaces of films, nanowires exhibit a distinct time-dependent photoluminescence quenching by over 90% within the time scale of seconds in the presence of air or dissociated liquids. This quenching is most pronounced for 50 nm diameter nanowires with interwire spacings larger than 500 nm due to internal electric field and external light field distributions. Ion- and pH-sensitive measurements, in combination with an externally applied voltage, allow the assignment of this effect to anions from the surroundings to accumulate at the nonpolar GaN side walls of the UV-exposed GaN nanowires. The decay times of the luminescence signal follow the dynamics of valence band holes, which deplete GaN surface states and positively charge the nanowire surfaces. This, in turn, induces the buildup of a capacitive anion shell around the nanowires, leading to an enhanced nonradiative surface recombination of photo-generated charge carriers from the GaN nanowire. In the absence of UV light, a recovery of the photoluminescence signal within tens of minutes indicates the dissolution of the anionic shell via charge balancing. The impact of light-induced electronic and ionic charge redistribution on photocarrier recombination represents an important mechanism of function for GaN nanowire-based devices, ranging from sensors to photocatalysts. [ABSTRACT FROM AUTHOR]

To achieve a high fill factor, a small diode factor close to 1 is essential. The optical diode factor determined by photoluminescence is the diode factor from the neutral zone of the solar cell and thus a lower bound for the diode factor. Due to metastable defects transitions, the optical diode factor is higher than 1 even at low excitation. Here, the influence of the backside recombination and the doping level on the optical diode factor are studied. First, photoluminescence and solar cell capacitance simulator (SCAPS) simulations are used to determine the back surface recombination velocity of Cu(In, Ga)Se2 with various back contacts and different doping levels. Then, experimental results and simulations show that both back surface recombination and high doping density reduce the optical diode factor. The back surface recombination reduces the optical diode factor with undesirable extra nonradiative recombination. The smaller value achieved by higher doping can increase quasi‐Fermi level splitting at the same time. The simulations show that the back surface recombination reduces the optical diode factor due to an illumination‐dependent recombination rate. In addition, a higher majority carrier doping reduces the influence of majority carrier gain from metastable defect transitions, thus reducing the optical diode factor. [ABSTRACT FROM AUTHOR]

The behavior of hole polarons in β -gallium oxide (Ga2O3) has attracted significant attention. Depth-resolved cathodoluminescence (CL) was used to investigate the minority carrier dynamics in β -Ga2O3. First, a model describing CL intensity was proposed by considering the depth-dose function and surface recombination. A universal depth-dose function for β -Ga2O3, which has the form of a third-degree polynomial, was presented based on Monte Carlo simulation by introducing a normalized depth, which is the depth normalized by the electron beam range. Second, two experimental approaches, plan-view and cross-sectional CL measurements, were applied to unintentionally doped β -Ga2O3 (âˆ'201) wafers, and the experimental results were compared with those of the proposed model. The hole diffusion length was estimated to be within the range of 200â€"400 nm through the plan-view measurement, whereas a hole diffusion length of 250 nm was obtained through the cross-sectional measurement. The values were consistent with each other, and the model reproduced the experimental results well. This indicates that the nonequilibrium minority hole in the unintentionally doped β -Ga2O3 is mobile and forms a ‘weak’ polaron. The reduced recombination velocity of the (âˆ'201) face was estimated to be approximately ten for the plan-view measurement, whereas that of ten or more was assumed for the cross-sectional measurement. No inconsistency was observed, but the low-energy plan-view measurement is considered more suitable for investigating the surface recombination velocity. [ABSTRACT FROM AUTHOR]

In a thermophotonic device used in an energy-harvesting configuration, a hot light-emitting diode (LED) is coupled to a photovoltaic (PV) cell by means of electroluminescent radiation in order to produce electrical power. Using fluctuational electrodynamics and the drift-diffusion equations, we optimize a device made of an AlGaAs PIN LED and a GaAs PIN PV cell with matched bandgaps. We find that the LED can work as an efficient heat pump only in the near field, where radiative heat transfer is increased by wave tunneling. A key reason is that non-radiative recombination rates are reduced compared to radiative ones in this regime. At 10 nm gap distance and for 100 cm s − 1 effective surface recombination velocity, the power output can reach 2.2 W cm − 2 for a 600 K LED, which highlights the potential for low-grade energy harvesting. [ABSTRACT FROM AUTHOR]

The efficient charge separation and surface state reactions are significant in enhancing the efficiency of photoelectrochemical hydrogen evolution. Herein, we report a ternary heterostructure consisting of CdS/ZnSe sensitized TiO2 nanorod as a photoanode. The heterojunction photoanode considerably widens the photon absorption spectral range and thereby enhances the photocurrent density up to 2 mA/cm2 at 1.23 V versus RHE which is 10 times higher than pristine TiO2 photoanode. The photoelectrochemical results demonstrate a high photocurrent density of 2 mA/cm2 with a photon‐to‐current conversion efficiency of 1.5 % at a very low applied bias (0.2 V vs RHE). The improved PEC performances of the multidimensional hybrid photoanode could be ascribed to the efficient visible‐light absorption of ZnSe and CdS nanocrystals decorated on the surface of 1D TiO2. The rapid electron‐transfer properties owing to higher carrier density, low carrier transport resistance, and an extended lifetime of photoexcited carriers in the multidimensional ZnSe/CdS/TiO2 heterostructure with suppressed surface charge recombination are responsible for enhanced hydrogen evolution activities. [ABSTRACT FROM AUTHOR]

In this paper, we report a novel design of bismuth nanoparticle-passivated silicon nanowire (Bi@SiNW) heterojunction composites for high diode performances and improved effective carrier lifetime and absorption properties. High-density vertically aligned SiNWs were fabricated using a simple and cost-effective silver-assisted chemical etching method. Bi nanoparticles (BiNPs) were then anchored in these nanowires by a straightforward thermal evaporation technique. The systematic study of the morphology, elemental composition, structure, and crystallinity provided evidence for the synergistic effect between SiNWs and BiNPs. Bi@SiNWs exhibited an eight-fold enhancement of the first-order Raman scattering compared to bare silicon. Current–voltage characteristics highlighted that bismuth treatment dramatically improved the rectifying behavior and diode parameters for Bi-passivated devices over Bi-free devices. Significantly, Bi wire-filling effectively increased the minority carrier lifetime and consequently reduced the surface recombination velocity, further indicating the benign role of Bi as a surface passivation coating. Furthermore, the near-perfect absorption property of up to 97% was achieved. The findings showed that a judicious amount of Bi coating is required. In this study the reasons behind the superior improvement in Bi@SiNW's overall properties were elucidated thoroughly. Thus, Bi@SiNW heterojunction nanocomposites could be introduced as a promising and versatile candidate for nanoelectronics, photovoltaics and optoelectronics. [ABSTRACT FROM AUTHOR]

A solar cell structure with a graded bandgap absorber layer based on InGaN has been proposed to overcome early predicted efficiency. Technological issues such as carrier concentration in the p- and n-type are based on the data available in the literature. The influence of carrier concentration-dependent mobility on the absorber layer has been studied, obtaining considerable improvements in efficiency and photocurrent density. Efficiency over the tandem solar cell theoretical limit has been reached. A current density of 52.95 mA/cm2, with an efficiency of over 85%, is determined for a PiN structure with an InGaN step-graded bandgap absorption layer and 65.44% of power conversion efficiency for the same structure considering piezoelectric polarization of fully-strained layers and interfaces with electron and hole surface recombination velocities of 10−3 cm/s. [ABSTRACT FROM AUTHOR]

BiVO4 has attracted wide attention for oxygen‐evolution photoanodes in water‐splitting photoelectrochemical devices. However, its performance is hampered by electron‐hole recombination at surface states. Herein, partially oxidized two‐dimensional (2D) bismuthene is developed as an effective, stable, functional interlayer between BiVO4 and the archetypal NiFeOOH co‐catalyst. Comprehensive (photo)electrochemical and surface photovoltage characterizations show that NiFeOOH can effectively increase the lifetime of photogenerated holes by passivating hole trap states of BiVO4; however, it is limited in influencing electron trap states related to oxygen vacancies (VO). Loading bismuthene on BiVO4 photoanodes increases the density of VO that are beneficial for the oxygen evolution reaction via the formation of oxy/hydroxyl‐based water oxidation intermediates at the surface. Moreover, bismuthene increases interfacial band bending and fills the VO‐related electron traps, leading to more efficient charge extraction. With the synergistic interaction of bismuthene and NiFeOOH on BiVO4, this composite photoanode achieves a 5.8‐fold increase in photocurrent compared to bare BiVO4 reaching a stable 3.4 (±0.2) mA cm–2 at a low bias of +0.8 VRHE or 4.7(±0.2) mA cm–2 at +1.23 VRHE. The use of 2D bismuthene as functional interlayer provides a new strategy to enhance the performance of photoanodes. [ABSTRACT FROM AUTHOR]

Passivation interlayers such as Al2O3 are required to improve the hole selectivity of dopant‐free passivating contact based on transition metal oxides. For the interlayer to provide low surface recombination as in conventional silicon heterojunctions (SHJs) or tunnel oxide passivated contact (TOPCon) technologies, "hydrogenation" strategies to effectively introduce hydrogen in passivation interlayers while being compatible with transition metal oxides (TMOs) are urgently sought after. In this work, an easy‐to‐implement strategy to successfully incorporate extra hydrogen in the Al2O3 passivation layer is developed. The chemical and field‐effect passivation mechanisms of the extra hydrogen are revealed via comprehensive experimental analyses and density functional theory calculations. By implementing H‐Al2O3 with Cu2O as the hole‐selective rear contact in p‐type crystalline silicon (c‐Si) solar cells, a remarkable efficiency of 20.35% is achieved (fill factor of 84.76%). The study highlights a promising approach to improve the passivation quality of dielectric interlayers and boost the performance of dopant‐free c‐Si solar cells to compete against mainstream c‐Si photovoltaics technologies. [ABSTRACT FROM AUTHOR]

Surface passivating thin films are crucial for limiting the electrical losses during charge carrier collection in silicon photovoltaic devices. Certain dielectric coatings of more than 10 nm provide excellent surface passivation, and ultra‐thin (<2 nm) dielectric layers can serve as interlayers in passivating contacts. Here, ultra‐thin passivating films of SiO2, Al2O3, and HfO2 are created via plasma‐enhanced atomic layer deposition and annealing. It is found that thin negatively charged HfO2 layers exhibit excellent passivation properties—exceeding those of SiO2 and Al2O3—with 0.9 nm HfO2 annealed at 450 °C providing a surface recombination velocity of 18.6 cm s−1. The passivation quality is dependent on annealing temperature and layer thickness, and optimum passivation is achieved with HfO2 layers annealed at 450 °C measured to be 2.2–3.3 nm thick which give surface recombination velocities ≤2.5 cm s−1 and J0 values of ≈14 fA cm−2. The superior passivation quality of HfO2 nanolayers makes them a promising candidate for future passivating contacts in high‐efficiency silicon solar cells. [ABSTRACT FROM AUTHOR]

The photocurrent spectra (PCS)of the ITO (indium tin oxide)/PEDOT:PSS(poly(3,4-ethylenedioxythiophene)-oly(styrenesulfonate))/P3HT:PCBM(poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester)/Al organic photovoltaic devices(OPVs) with six different thicknesses of P3HT:PCBM layer, ranging from 80 to 345 nm,were measured under monochromatic visible light for the reverse voltage range from - 4 to 0 V .The measured PCS showed a good correlation with the P3HT:PCBM absorption spectrum for thinner devices, while for thicker OPVs a pronounced red shift in PCS was observed. As this PCS behavior is usually explained by the surface recombination effects at electrode contacts, a drift–diffusion model (DDM), which includes charge carrier surface recombination and thermal injection on the anode and cathode through boundary conditions, was used for the PSC simulations. The experimentally obtained normalized PCS were very well reproduced by the DDM when absorption and charge carrier photogeneration in P3HT:PCBM thin films were assumed to follow the Beer-Lambert law, and surface recombination at electrode contacts was negligible. Further, the effect of surface recombination on normalized PCS was analyzed in detail by reducing the surface recombination velocity (SRV) in the DDM calculations for either majority or minority charge carriers at one of the electrodes. Also, the DDM calculations were conducted for the cases of electron dominated, balanced, and hole dominated transport in the OPVs active layer. It was concluded that only the reduction of SRV for majority carriers at the electrode which extracts faster carriers affects the normalized PCS. For balanced hole and electron transport the surface recombination had no influence on the normalized PCS. [ABSTRACT FROM AUTHOR]

Passivating contacts based on transition metal oxides (TMOs) have the potential to overcome existing performance limitations in high‐efficiency crystalline silicon (c‐Si) solar cells, which is a significant driver for continuing cost/Watt reductions of photovoltaic electricity. Herein, innovative stacks of Al‐alloyed TiOx (AlyTiOx) and pure TiOx as transparent electron‐selective passivating contacts for n‐type c‐Si surfaces are explored. An optimized stack of 2 nm AlyTiOx and 2 nm TiOx is shown to provide both record‐quality surface passivation and excellent electrical contact, with a surface recombination current density prefactor J0 of 2.4 fA cm−2 and a specific contact resistivity ρc of 15.2 mΩ cm2. The performance of this innovative stack significantly exceeds previously reported values for pure or doped TiOx single layers, SiOx/TiOx stacks, a‐Si:H/TiOx stacks, and other transparent contact technologies. Furthermore, an excellent efficiency of 21.9% is attained by incorporating the optimized stack as a full‐area rear contact in an n‐type c‐Si solar cell. The findings set a new benchmark for the passivation performance of metal oxide‐based passivating contacts, bringing it to a level on par with state‐of‐the‐art SiOx/poly‐Si contacts while greatly improving optical transparency. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted wide attention due to their capacity to achieve high‐power conversion efficiencies. However, the high trap‐assisted recombination taking place in the active layer leads to performance loss in PSCs. In particular, the excessive recombination at the interface between the perovskite active layer and the carrier selective contacts can be especially problematic. Therefore, the identification of the dominant recombination pathways in a given PSC architecture is of significant importance for the mitigation of losses and enhancement of device performance. Here, we introduce an approach for identifying the dominant recombination pathways in PSCs by applying illumination‐side‐dependent impedance spectroscopy (ISD‐IS) measurements on the devices with a semi‐transparent top electrode. We validate this technique using coupled ionic‐electronic numerical simulations and apply it experimentally on a standard PSC structure. Overall, this approach could be of significant importance for pinpointing the performance bottlenecks in PSC devices under operationally relevant conditions and providing a more detailed picture of the losses in a complete PSC device by examining its behaviors under illumination from both sides at different operation conditions, which could allow for a more targeted optimization strategy of PSCs to improve their performance. [ABSTRACT FROM AUTHOR]

A model of the energy balance of a microparticle located in the plasma of an electric discharge in neon is proposed which considers the heating of a microparticle as a result of collisions with electrons and ions, recombination, and quenching of metastable atoms on its surface. Plasma parameters are calculated using a liquid model of a low-pressure discharge in neon with microparticles. The increase in temperature of microparticles with a diameter of 2.55 μm, which form clouds in plasma at a concentration of 104–105 cm–3 obtained in experiments at a neon pressure of 40–120 Pa and discharge current 0.5–2.0 mA, is calculated. It is established that the contribution of the quenching of metastable atoms to the heating of a microparticle increases with increasing pressure and can be about 40% of the heating associated with recombination on its surface. [ABSTRACT FROM AUTHOR]

Larger solar cells are preferred for higher power output. However, they produce higher current and lead to higher ohmic loss. This loss has prompted manufacturers to laser cut cells into halved cells, resulting in lower current, higher voltage string‐cells. While these techniques reduce ohmic loss, they introduce cutting‐edge recombination. The monolithic solar cell resembles halved cell but without requiring cutting the original cell into strings of cells which saved the cutting‐edge recombination loss. However, we observed that the interconnection of base regions of the string‐cells on the same wafer leads to problems such as lateral forward bias current, resulting in severe degradation of the fill factor (FF) and open‐circuit voltage (VOC). Solutions to these issues are proposed including depassivated surfaces between string‐cells, optimized spacing between the string‐cells, lowered base doping density, thinner wafers, and shading regions between the string‐cells. According to simulation results, these methods could increase the efficiency of the monolithic cell to very close to the baseline cell. With the consideration of the reduced shading, ohmic loss, and module blank areas on the cell‐to‐module process, the efficiency of a module with monolithic cells could exceed that of a module with baseline cells or a module of halved/shingling cells. [ABSTRACT FROM AUTHOR]

A tridimensional mathematical model to calculate the electron beam induced current (EBIC) of an axial p-n nanowire junction is proposed. The effect of the electron beam and junction parameters on the distribution of charge carriers and on the collected EBIC current is reported. We demonstrate that the diffusion of charge carriers within the wire is strongly influenced by the electrical state of its lateral surface which is characterized by a parameter called surface recombination velocity (v r). When the surface recombination is weak (i.e. low v r value), the diffusion of charge carriers occurs in one dimension (1D) along the wire axis, and, in this case, the use of bulk EBIC models to extract the diffusion length (L) of charge carriers is justified. However, when the surface effects are strong (i.e. high v r values), the diffusion happens in three dimensions (3D). In this case, the EBIC profiles depend on v r value and two distinct cases can be defined. If the L is larger than the nanowire radius (r a), the EBIC profiles show a strong dependency with this parameter. This gives evidence that the recombination of generated carriers on the surface through v r is the dominant process. In this situation, a decrease of two orders of magnitude in the EBIC profiles computed with a high and a low v r value is observed in neutral regions of the junction. For the case of L smaller than r a the dependency of the EBIC profiles on the v r is weak, and the prevalent recombination mechanism is the bulk recombination process. [ABSTRACT FROM AUTHOR]

The electrical and passivation properties of alumina layers deposited by the atomic layer deposition (ALD) technique with different precursors at different temperatures are analyzed. Herein, a significantly larger density of the negative fixed charge in alumina layers deposited with ozone in comparison to those prepared with water is observed. A part of this negative charge can be successfully removed by the annealing of the samples already at around 250 °C and this negative charge is tentatively ascribed to oxygen interstitials. The effective surface recombination velocity (seff) is below 2 cm s−1 in all as‐deposited alumina layers independent of the deposition conditions and it is significantly smaller in layers prepared with water. The higher seff in films prepared with ozone can be explained by the higher density of the interface states in these samples as obtained from impedance measurements performed at different ac frequencies and at different biases. The conduction mechanisms in alumina films are also investigated and their difference is discussed. [ABSTRACT FROM AUTHOR]

The exploration of two-dimensional (2D) materials in highly performance optoelectronic device is critical for the practical applications. Traditionally, GaN related semiconductors uses complicated multiple quantum wells to increase the overlap of electron and hole waves for highly efficient light emitting diode (LED). In this work, through designing the Graphene/MoS 2 heterostructure for increasing the hot electron lifetime and subsequently enhancing the process of carrier multiplication (CM), we successfully realize the highly efficient Graphene/MoS 2 /p-GaN LED with external quantum efficiencies (EQE) of 15.89% under 0.625 mA/mm2. Compared with the Graphene/p-GaN LED device, the addition of MoS 2 leads to stronger light output and the maximum EQE increased by 61%. The energy bands alignment between MoS 2 and GaN squeezes the hole at the MoS 2 layer, when the numbers of holes are increased by graphene as a result of CM effect, which recombines with electron at the surface of GaN defects resulting in the strong light output at reversed bias. We believe that this work will bring a brand new insight of realizing high efficient 2D materials based LED and optoelectronic devices. [Display omitted] • We successfully realize hot carriers assisted mixed-dimensional Graphene/MoS 2 /p-GaN LED. • The CM effect in the Graphene effectively increases the accumulation of carriers at the junction area between the MoS 2 and p-GaN. • The radiative recombination on the surface of p-GaN improve the EQE. [ABSTRACT FROM AUTHOR]

Interfacial engineering is extensively used to reduce the interfacial loss caused by surface recombination, improve the crystallinity of the active absorption layer, and enhance the long‐term stability of perovskite solar cells (PSCs). Solution processing techniques, such as spin coating and dip coating, are commonly used to deposit the interfacial layer because of their cost‐effectiveness and simplicity. Although determining suitable solutes for use in these processes is important, selecting appropriate solvents is also crucial. Herein, commonly used solvents are investigated to determine optimal solvents for solution processing by categorizing them into nonpolar and polar groups. The results suggest that the efficiency of the PSCs can be increased by simple solvent treatment. In particular, the efficiencies of systems subjected to hexane (nonpolar) and ethanol (polar) treatment are significantly improved (17.31% and 17.44%, respectively) compared with that of a control device (16.24%). Herein, the effects of pure solvents on the SnO2–perovskite interface are confirmed and an important direction for investigations that adopt solution processing to improve the efficiency of PSCs, such as research on interlayers and self‐assembled monolayers, is suggested. [ABSTRACT FROM AUTHOR]

The structural design of photosensitizers for dye‐sensitized solar cells (DSSCs) usually involves modification of the donor and π‐spacer moieties using expensive Pd crosscoupling reactions. Herein, the concept of more sustainable and cost‐effective dyes to realize large‐scale production is presented. Two dyes, coded BzC and PTZC, with low‐cost donors, phenyl and phenothiazine, respectively, and 4H‐cyclopenta[2,1‐b:3,4‐b']dithiophene π‐spacer, are synthesized by Pd‐free reactions, including Horner–Wadsworth–Emmons, with high overall yield (68% for BzC and 55% for PTZC). The best photovoltaic performances exhibit 3.00% and 5.92% together with relatively low ideality factor of 1.03 and 1.12 for BzC and PTZC, respectively, indicating efficient retardation of electron recombination from surface trap states. Finally, the synthesis costs for BzC and PTZC are estimated to be about 7.5–9 times lower than that of LEG‐4 (as a commercial reference dye). The cost performances of BzC and PTZC are estimated to be around 5 times better than that of LEG‐4. [ABSTRACT FROM AUTHOR]

The reliability of Ge photodetectors used in the framework of Si photonics is studied using TCAD simulation, in order to better understand the physical origin of dark current and responsivity degradation observed in Sy et al. (2019). It is shown that bulk and interface recombination mainly modify the SRH dominated dark and light currents, while fixed charge and $\text{D}_{\mathrm{ it}}$ strongly impacts band-to-band tunneling dark currents. This essential distinction shows the necessity to discriminate the dominating transport mechanisms in photodetectors using activation energy measurement, in order to better identify the origin of performance degradation. It also strengthens the requirement for adequate passivation of all interfaces to reach higher lifetime of photodetectors. [ABSTRACT FROM AUTHOR]