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Perovskite solar cells (PSCs) continue to be the "front runner" technology among emerging photovoltaic devices in terms of power conversion efficiency and versatility of applications. However, improving stability and understanding their relationship with their ionic–electronic transport mechanisms continue to be challenging. In this work, a case study of NiOx-based inverted PSCs and the effect of different interface passivating treatments on device performance is presented. Impedance spectroscopy (IS) measurements in short-circuit conditions were performed under different illumination intensities, as well as bias-stress operational stability tests under constant illumination intensity. Surface treatments that involved bulky Lewis bases resulted in better and more stable performance. In contrast, acidic anion donors could induce both an initial performance decrease with a characteristic three-arcs impedance Nyquist plot and a subsequent instability during light exposure. Drift–diffusion simulations suggest strong modifications of surface recombination at the interface with the hole transport material, and for the ion concentration and mobilities in the perovskite. Importantly, capacitance and resistance are shown to peak maximum and minimum values, respectively, around mobile ion concentration (Nion) of 1016 and 1017 cm−3. These features relate to the transition from a drift-, for low Nion below a threshold value, to a diffusion-dominated transport in the bulk of the perovskite, for high Nion beyond the threshold value. Our results introduce a general route for characterization of instability paths in PSCs via IS performed under short-circuit conditions. [ABSTRACT FROM AUTHOR]

InGaN micro-LEDs (μ LEDs) with their potential high-volume applications have attracted substantial research interest in the past years. In comparison to other III–V semiconductors, InGaN exhibits a reduced susceptibility toward non-radiative surface recombination. However, efficiency degradation becomes more prominent as dimensions shrink to a few μ m or less. Due to the high surface-to-volume ratio of the miniaturized devices, the non-radiative recombination increases and reduces the internal quantum efficiency. While many groups focus on surface passivation to mitigate surface defects, the influence of crystallographic orientation of the μ LED sidewall on the efficiency remains unexplored. This study addresses this gap by investigating the impact of crystallographic orientation of the sidewalls on the emission properties of the μ LEDs. Hexagonal and elongated μ LEDs with dimensions as small as 3.5 μ m and sidewalls with crystallographically well-defined m- and a-planes were fabricated. Electrical and optical properties were investigated using photo- and electroluminescence. External quantum efficiency (EQE) is assessed based on well-known carrier recombination models. It can be shown that μ LED performance intrinsically depends on the crystallographic orientation of the sidewalls. Comparing hexagonal μ LED structures with a-plane and m-plane sidewalls, an increase in the EQE by 33 % was observed for structures with a-plane sidewalls, accompanied by reduction in the current density of the peak EQE by a nearly two orders of magnitude compared to structures with m-plane sidewalls. By analyzing the EQE characteristics at the μ LED center and near the sidewalls, the improvements can be directly attributed to the increased radiative recombination from sidewalls with a-plane orientation. [ABSTRACT FROM AUTHOR]

We introduce a multiple-carrier-lifetime model (MCLM) for light-emitting diodes (LEDs) with non-uniform carrier distribution, such as in multiple-quantum-well (MQW) structures. By employing the MCLM, we successfully explain the modulation response of V-pit engineered MQW LEDs, which exhibit an S21 roll-off slower than −20 dB/decade. Using the proposed model and employing a gradient descent method, we extract effective recombination and escape lifetimes by averaging the carrier behavior across the quantum wells. Our results reveal slower effective carrier recombination and escape in MQW LEDs compared with LEDs emitting from a single QW, indicating the advantages of lower carrier density achieved through V-pit engineering. Notably, the effective carrier recombination time is more than one order of magnitude lower than the effective escape lifetime, suggesting that most carriers in the quantum wells recombine, while the escape process remains weak. To ensure the reliability and robustness of the MCLM, we subject it to a comprehensive threefold validation process. This work confirms the positive impact of spreading carriers into several quantum wells through V-pit engineering. In addition, the MCLM is applicable to other LEDs with a non-uniform carrier distribution, such as micro-LEDs with significant surface recombination and non-uniform lateral carrier profiles. [ABSTRACT FROM AUTHOR]

It is a formidable challenge to find the minority carrier recombination lifetime in low-dimensional devices as low-dimensionality increases the surface recombination rate and often reduces the recombination lifetime to a scale of picoseconds. In this work, we demonstrated a simple but powerful method to quantitatively probe the minority carrier recombination lifetime in silicon nanowires or microwires by fitting the experimental photoresponses with our recently established analytical photoresponse principle of photoconductors. The nanowires were passivated with small molecules and Al2O3 to suppress surface recombination, which will increase the minority recombination lifetimes. As expected, the minority carrier recombination lifetime found by this approach increases by orders of magnitude. These wires were also made into PIN diodes, the leakage of which was reduced at least 1 order of magnitude after surface passivation by Al2O3. The minority recombination lifetime found from the leakage current of these devices is largely consistent with what we found from our analytical photoresponse principle. As a further step, we performed scanning photocurrent microscopy to find the minority diffusion length from which we found that the minority recombination lifetime is close to what we found from the analytical photoresponses. In short, this work validated that our analytical response principle is a reliable method to find the minority recombination lifetime in low-dimensional semiconductors. [ABSTRACT FROM AUTHOR]

This work reports a study of the passivation effects of different dielectric thin films deposited on monocrystalline CdTe/MgCdTe double heterostructures (DHs) using atomic layer deposition (ALD). Enhanced photoluminescence intensity was observed in all DHs with surface passivation, and increased photogenerated carrier lifetime was observed in DHs with HfO2, TiO2, Al2O3, and TiN passivated CdTe/MgCdTe DHs. These results have demonstrated effective suppression of the undesired surface recombination of CdTe/MgCdTe DHs by dielectric thin films deposited via ALD. [ABSTRACT FROM AUTHOR]

Sluggish kinetics of photoexcited charge carriers in photocatalysts, slow hole transfer in oxidation half‐reaction, and consequent fast charge recombination on photocatalyst surface are the Achilles' heel limiting the efficiency of photocatalytic hydrogen evolution (PHE). Herein, the effectiveness of covalent binding alternating D‐A‐D organic small molecules (triphenylamine as the donor unit and benzothiadiazole as the acceptor unit) to Znln2S4 (ZIS) nanosheets in the design and development of highly efficient PHE photocatalysts is demonstrated. The covalent grafting of D‐A‐D molecules broadens the photo‐responsive range of ZIS nanosheets, significantly increasing the density of photogenerated charge carriers. More importantly, D‐A‐D organic small molecules can efficiently extract surface photogenerated holes and suppress the recombination of surface photogenerated electron‐hole pairs, thus facilitating the rapid consumption of retained photogenerated electrons for proton reduction to generate H2 with fast kinetics. Consequently, the optimized PHE rate of the ZIS@DAD hybrid catalyst reaches 28.25 mmol g−1 h−1, a 4.2‐fold improvement over that of ZnIn2S4 nanosheets. The covalent integration of D‐A‐D molecules onto inorganic semiconductor photocatalysts represents a novel and highly efficient strategy for optimizing the overall PHE process. This approach provides a fertile new ground for creating efficient solar‐to‐hydrogen systems. [ABSTRACT FROM AUTHOR]

Knowledge regarding the temperature dependence of the surface recombination at the interface between silicon and various dielectrics is critically important as it 1) provides fundamental information regarding the interfaces and 2) improves the modeling of solar cell performance under actual operating conditions. Herein, the temperature‐ and carrier‐dependent surface recombination at the silicon–oxide/silicon and aluminum–oxide/silicon interfaces in the temperature range of 25−90 °C using an advanced technique is investigated. This method enables to control the surface carrier population from heavy accumulation to heavy inversion via an external bias voltage, allowing for the decoupling of the bulk and surface contributions to the effective lifetime. Thus, it offers a simple and versatile manner to separate the chemical passivation from the charge‐assisted population control at the silicon/dielectric interface. A model is established to obtain the temperature dependence of the capture cross sections, a critical capability for the optimization of the dielectric layers and the investigation of the fundamental properties of the passivation under field operating conditions. [ABSTRACT FROM AUTHOR]

With the improvement of surface passivation, bulk recombination is becoming an indispensable and decisive factor to assess the theoretical limiting efficiency (ηlim) of crystalline silicon (c‐Si) solar cells. In simultaneous consideration of surface and bulk recombination, a modified model of ηlim evaluation is developed. Surface recombination is directly depicted with contact selectivity while bulk recombination is revised on the aspects of ideality factor and wafer thickness. The ηlim of the double‐side silicon heterojunction (SHJ) and double‐side tunneling‐oxide passivating contact (TOPCon) solar cells are numerically simulated using the new model as 28.99% and 29.19%, respectively. However, the ηlim of single‐side TOPCon solar cells, the more practicable scenario, is only 27.79%. Besides, the ηlim of the double‐side SHJ solar cells would exceed the double‐side TOPCon solar cells if the recombination parameter of the non‐contacted area is higher than 0.6 fA/cm2, instead of perfect passivation. Our results are instructive in accurately assessing efficiency potential and accordingly optimizing design strategies of c‐Si solar cells. [ABSTRACT FROM AUTHOR]

Wide-bandgap semiconductors are regarded as preferred materials for preparing semiconductor conversion devices in betavoltaic batteries due to their high theoretical conversion efficiency (ηc). However, there are a few comprehensive analytical studies on why the experimental values of ηc are generally much lower than the theoretical limit of ηc (ηc-limit) and how to improve ηc and its stability. In this work, combined with the energy deposition distributions of Ti3H2, 63Ni, and 147Pm2O3 radioactive sources in SiC obtained from Monte Carlo simulations, a multi-physical mechanism, multi-parameter coupling numerical model was established. This model can comprehensively analyze the output characteristics of betavoltaic batteries under the influence of actual device structural and material parameter changes. Our results show that changes in structural and material parameters cause significant variations in the collection efficiency (Q) of the radiation-generated electron–hole pair (RG-EHP). Considering structural parameters are easy to control, instabilities in actual SiC material parameters, which include electron diffusion length (Ln), hole diffusion length (Lp), and surface recombination velocity (S), are the main reason that ηc fluctuates significantly and is generally far lower than ηc-limit. Due to differences in the distribution of RG-EHP produced by different radioactive sources in SiC, the dominant parameters causing ηc fluctuations differ. By analyzing differences in recombination loss mechanisms under different radioactive sources, the device structures were designed in a targeted manner to make ηc closer to ηc-limit. Meanwhile, when the SiC material quality fluctuates, the stability of ηc increases by 58.5%, 35.3%, and 48.2% under Ti3H2, 63Ni, and 147Pm2O3, respectively. [ABSTRACT FROM AUTHOR]

Hafnium oxide (HfOx) films grown by atomic layer deposition (ALD) have recently been demonstrated to provide high‐quality silicon surface passivation. Reports have suggested that changing the composition of the hafnium‐containing precursor can enable films of both charge polarities to be produced. Herein, the passivation quality of hafnium oxide grown with metal amide precursors and a tetrakis(ethylmethylamido)hafnium (TEMAHf) precursor is examined, considering film charge polarity, chemical‐ and field‐based passivation effects, and film crystallinity. Throughout, the properties of TEMAHf‐HfOx are benchmarked against that of hafnium oxide grown with a tetrakis(dimethylamido)hafnium precursor. It is found that precursor choice has no influence on the fixed negative charge polarity (of order −1012 q cm−2) of HfOx films grown via plasma‐enhanced ALD. TEMAHf‐HfOx passivation is influenced by post‐deposition annealing temperature and can passivate with a surface recombination velocity ≤3 cm s−1 on n‐type silicon, compared to surface recombination velocities ≤11 cm s−1 for TDMAHf‐HfOx of a similar thickness. [ABSTRACT FROM AUTHOR]

The explanation of the n-type silicon thermoelastic photoacoustic response is given by electro-acoustic analogies, which clarify the influence of excess free carriers as heat carriers. It was found that electro-acoustic analogies could interconnect different theoretical models of heat flow and carrier dynamics aiming to find the optimal experimental conditions for the efficient free carrier influence analysis of the sample thermoelastic photoacoustic response. Theoretical analysis was based on the comparison between the composite piston, surface recombination, and RC filter frequency response models, extrapolating the behavior of the photoacoustic response much beyond the experimental frequency domain. Experimental analysis was based on the open-cell photoacoustic setup operating under the transmission configuration within the modulation frequencies range from 20 Hz to 20 kHz. The accuracy of our predictions and the validity of electro-acoustic analogies are confirmed by measuring 875 μm plasma-thick and 35 μm plasma-thin silicon samples. [ABSTRACT FROM AUTHOR]

Metal-assisted chemical etching (MACE) with platinum nanoparticles (Pt-NPs) was used to produce cone-shaped macropore structures (CSMS) on the surface of p-type silicon substrates. A straightforward control of the macropore dimensions is readily obtained as the etching time is tuned during the MACE process. The surface reflectance is advantageously reduced in a wide wavelength range and a minimum of 6.6% was achieved for an etching time of 9 min. The impact of the etching current on the morphological and optical properties of the textured Si wafers was also studied, revealing a substantial decrease of the surface reflectance up to an etching current of 40 mA. Moreover, an increase of the effective minority carrier lifetime from 5.9 to 8.9 µs was obtained as the etching current increases from 5 to 50 mA, indicating a reduction of surface recombination with the enlargement of the macropores. Interestingly, the field-effect passivation of the CSMS was found to significantly increase the effective carrier lifetime by reducing the surface recombination. [ABSTRACT FROM AUTHOR]

The effects of surface recombination on the steady-state carrier profiles and photocurrent in perovskite solar cells are investigated in this paper. The continuity equations for both holes and electrons are solved considering carrier drift and diffusion under the exponential carrier generation profile in the perovskite layer and considering both bulk and interface carrier recombination. An analytical expression for the solar-induced photocurrent is derived. The rate of carrier recombination at the interfaces has a very significant effect on the carrier profile, photocurrent, and, hence, on the charge collection efficiency. The external current density is calculated considering the dark current and nominal solar spectrum-induced photocurrent. The proposed model is fitted and verified with published experimental results from various publications. The fittings of the model with experimental results provide information about the interface and bulk charge carrier transport parameters. [ABSTRACT FROM AUTHOR]

Conventional silicon junction detectors encounter significant carrier recombination within the heavily doped p+ and n+ layers, as well as beneath the metal contact regions, creating the so-called "dead layers", especially on the detector side. In this study, we present the tunnel oxide passivating contact with doped polysilicon on oxide, which demonstrates exceptional surface passivation and carrier selectivity. The key innovation lies in an ultra-thin (~ 1.5 nm) interfacial oxide layer that facilitates efficient majority carrier transportation via tunneling while effectively block minority carriers. Remarkably low saturation current densities, ranging from 5 to 10 fA/cm2 even with the metal contact, underscore the superiority of both n-type and p-type tunnel oxide passivating contacts. In contrast, conventional p–n junction or high-low junction exhibit saturation current densities ranging from 10 to 90 fA/cm2 in the studied p+ and n+ layers with surface passivation schemes due to Auger recombination and surface recombination, and 1000–6000 fA/cm2 with metal contacts due to intense metal-induced recombination at the interface. These findings indicate the potential and superiority of implementing n-type tunnel oxide passivating contact on the detector side and p-type contact on the back side for advanced silicon radiation detectors. This approach would enable thorough collection of generated charge carriers along the track of incident ionizing radiation particles, leading to improved energy resolution and reduced noise levels. [ABSTRACT FROM AUTHOR]

Low degradation rate for a long degradation time and poor cycle stability caused by rapid recombination of generated electron-hole pairs are tough challenges for photo-Fenton degradation The unique microstructure catalyst can provide enough catalytic surface to prevent the recombination of electron-hole pairs and facilitate the barrier-free transport of active species. In addition, the special hollow microsphere structure can effectively accelerate the Rhodamine B (RhB) penetration and the photo-Fenton process. Introducing SrWO 4 can increase oxygen vacancies and optimize the electronic structure of ZnFe 2 O 4 , thus enhancing electron transport and RhB degradation in the photo-Fenton process. This kind of catalytic material ZnFe 2 O 4 /SrWO 4 (ZFO/SW) in the photo-Fenton process can effectively degrade the 99.18 % RhB dye only within 20 min with remarkable cycling stability. This work demonstrates the high efficiency of ZFO/SW as a photocatalyst and confirms the contribution of the current design concept to the development of photo-Fenton degradation materials. [ABSTRACT FROM AUTHOR]

• Dust-neutral collision decreases the growth rate of the ultra low-frequency mode. • The effect of dust-neutral collision is insignificant in the higher frequency mode. • The instability stabilizes due to finite electron and ion inertia. • Recombination at dust particle's surface has negligible effect on the instability. The dust acoustic drift instability has been investigated at the lower electrojet region of the dusty ionosphere by considering a linearized fluid model. The effect of dust-neutral collisions, electron–ion recombination at the surface of the dust particles, and electron and ion inertia on the onset and growth of the instability have been explored in minutiae. The perturbed densities are gleaned from the electron, ion, and dust dynamics, which engendered generalized dispersion relations. The generalized dispersion relation delineates the propagation of low-frequency dust acoustic drift waves. The dispersion relation is solved numerically for various cases of interest at the two different altitudes(∼ 90 km and ∼ 100 km) of the lower electrojet region. It has been found that the instability is unlikely to develop due to recombination alone, similar as observed in the case of laboratory dusty plasma. A significant reduction of the growth rate has been observed in the low-frequency mode due to the dust-neutral collision both in the presence and absence of an equilibrium electron density gradient. However, the effect of dust-neutral collision is not discernible in the relatively higher frequency mode, which exists at an altitude of 100 km. Moreover, the presence of electron and ion inertia has a stabilizing effect on the instability. The analysis presented here is germane to the lower ionospheric dusty electrojet region in which electrons are magnetized, but ions and dust particles are unmagnetized. [ABSTRACT FROM AUTHOR]

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors. [ABSTRACT FROM AUTHOR]

The contribution of minority charge carriers (electrons) is taken into account in the evaluation of thermo-electromotive force (thermo-E.M.F.) of a non-degenerate p -type semiconductor in the stationary state and when the quasi-neutrality condition is fulfilled. The results obtained show that the contribution to the thermo-E.M.F. due to the presence of minority electrons is a function of the bandgap and the length of the semiconductor used. It also depends on the minority carriers through their electrical conductivity, thermal conductivity, Seebeck coefficient, and bulk and surface recombinations. That contribution tends to reduce the principal thermo-E.M.F. (α p Δ T) of the p -type semiconductor and will, therefore, be called counter-thermo-electromotive force (counter-thermo-E.M.F.). The calculations made in the case of silicon give a counter-thermo-E.M.F. of magnitude generally non-negligible, which decreases when the length of the silicon and the concentration of doping elements increase. Finally, it is shown that the best way to minimize the counter-thermo-E.M.F. is to treat the surface of the semiconductor to promote the recombination of minority carriers there. [ABSTRACT FROM AUTHOR]

We demonstrate high-speed mid-wave infrared photoconductive detectors leveraging a lattice-mismatched, epitaxially grown InSb absorber material patterned with nanometer-scale hole arrays. We show that the nano-scale hole patterns allow for post-growth control over the detector response time by introducing recombination surfaces to increase non-radiative recombination. The photoconductive pixels are integrated into a microwave coplanar waveguide for high frequency characterization. The detector response is characterized as a function of temperature and hole-array dimensions. We show a detector response with characteristic time scales of tens of picoseconds and bandwidths up to 7 GHz at room temperature. The presented detectors offer a mechanism for engineering response times in long wavelength detectors for potential applications in high-speed sensing/imaging, free-space communication, ranging, or dual-comb spectroscopy. [ABSTRACT FROM AUTHOR]

High‐efficiency Cu(In,Ga)Se2 solar cells rely on Ga grading to mitigate back surface recombination. However, the inhomogeneous absorber has drawbacks, including increased non‐radiative loss and inadequate absorption. Therefore, literatures demand a paradigm shift of using a hole‐transport layer to passivate the back surface. Herein, a functional hole‐transport layer is demonstrated as an alternative to Ga grading. The novel hole‐transport layer is prepared as a double‐layer: co‐evaporated CuGaSe2 covered by solution combustion synthesis prepared In2O3. As demonstrated by micrographs, elemental mapping, and photoluminescence spectroscopy, the oxide layer improves thermal stability and prevents Ga diffusion. However, during the absorber deposition, a complete ion exchange of In and Ga converts CuGaSe2/In2O3 into CuInSe2/GaOx. Incorporating this hole‐transport layer in co‐evaporated nongraded CuInSe2 solar cells leads to significantly increased minority carrier lifetime from 5 to 113 ns, yielding an 80 meV improvement in quasi‐Fermi‐level splitting. The devices exhibit improved open‐circuit voltage, as well as a promising fill factor of over 71%, indicating good hole‐transport properties. In these results, the passivation effect and good hole‐transport properties of the hole‐transport layer are experimentally demonstrated. Thus, high‐efficiency solar cells can be achieved by using a functional hole‐transport layer without relying on Ga grading. [ABSTRACT FROM AUTHOR]

A special micro LED whose light emitting area is laid out in a U-like shape is fabricated and integrated with colloidal quantum dots (CQDs). An inkjet-type machine directly dispenses the CQD layer to the central courtyard-like area of this U-shape micro LED. The blue photons emitted by the U-shape mesa with InGaN/GaN quantum wells can excite the CQDs at the central courtyard area and be converted into green or red ones. The U-shape micro LEDs are coated with Al2O3 by an atomic layer deposition system and exhibit moderate external quantum efficiency (6.51% max.) and high surface recombination because of their long peripheries. Low-temperature measurement also confirms the recovery of the external quantum efficiency due to lower non-radiative recombination from the exposed surfaces. The color conversion efficiency brought by the CQD layer can be as high as 33.90%. A further continuous CQD aging test, which was evaluated by the strength of the CQD emission, under current densities of 100 A/cm2 and 200 A/cm2 injected into the micro LED, showed a lifetime extension of the unprotected CQD emission up to 1321 min in the U-shape device compared to a 39 min lifetime in the traditional case, where the same CQD layer was placed on the top surface of a squared LED. [ABSTRACT FROM AUTHOR]

Trypanosoma cruzi is the causative agent of Chagas disease, which causes 10,000 deaths per year. Despite the high mortality associated with Chagas, relatively few parasite genomes have been assembled to date, with genome assemblies unavailable even for some commonly used laboratory strains. This is at least partially due to T. cruzi 's highly complex and highly repetitive genome, which defies investigation using traditional short-read sequencing methods. In this study, we have generated a high-quality whole-genome assembly of the hybrid Tulahuen strain, a commercially available type VI strain, using long-read Nanopore sequencing without short-read scaffolding. The assembled genome contains 25% repeat regions, 17% variable multigene family members, and 27% transposable elements (TEs) and is of comparable quality with T. cruzi genome assemblies that utilized both long- and short-read data. Notably, we find that regions with TEs are significantly enriched for multicopy surface proteins, and that surface proteins are, on average, closer to TEs than to other coding regions. This finding suggests that mobile genetic elements such as transposons may drive recombination within surface protein gene families. This work demonstrates the feasibility of Nanopore sequencing to resolve complex regions of T. cruzi genomes, and with these resolved regions, provides support for a possible mechanism for genomic diversification. [ABSTRACT FROM AUTHOR]

In this study, a picosecond (ps) laser (wavelength 532 nm) with a top-hat beam was used to ablate a dielectric stack on a polished surface to improve the quality of the ablated surface. Homogeneous removal was achieved at an appropriate fluence for the ablation, since the uniform absorption of laser energy in the stack occurred by using a top-hat beam and a polished surface process. When the fluence was in the range of 0.51–0.74 J/cm2 for a top-hat beam, the direct ablation played a leading role, since more energy was absorbed in the stack rather than in the silicon, resulting in minimum damage. However, the surplus peak fluence of a ps laser with a Gaussian beam penetrated the stack and consequently caused heat shock to the silicon, and partial lift-off ablation generated thermal damage with a depth of more than 2 μm. Average efficiency of 23.40% for the passivated emitter and rear contact (PERC) cells applied with the superior ablation exceeded that for the reference cells applied with the nanosecond laser ablation with a Gaussian beam by 0.11% absolute. The significant improvement of open-circuit voltage (Voc), short-circuit current (Isc) and fill factor (FF) was mainly due to the reduced recombination at the rear contacts and decreased leakage current. The mechanisms of the laser ablation with a top-hat beam resulting in reduced damage are also applicable to other lasers with different wavelengths and can be used for improving the efficiency of other cells where a low level of damage in the ablation process is needed to decrease the surface recombination. [ABSTRACT FROM AUTHOR]

A world record conversion efficiency of 26.81% has been achieved recently by LONGi team on a solar cell with industry-grade silicon wafer (274 cm2, M6 size). An unparalleled high fill factor (FF) of up to 86.59% has also been certified in a separated device. The theoretical FF limit has been predicted to be 89.26%, while the practical FF is far below this limit for a prolonged interval due to the constraints of recombination (i.e., SRH recombination) and series resistance. The ideality factor (m) in the equivalent circuit of silicon solar cells is consistently ranging from 1 to 2 and rarely falls below 1, resulting in a relatively lower FF than 85%. Here, this work complements a systematic simulation study to demonstrate how to approach the FF limit in design of silicon solar cells. Firstly, a diode component with an ideality factor equal to 2/3 corresponding to Auger recombination is incorporated in the equivalent circuit for LONGi ultra-high FF solar cell; Secondly, an advanced equivalent circuit is put forward for comprehensive analysis of bulk recombination and surface recombination on the performance, in which specific ideality factors are directly correlated with various recombination mechanisms exhibiting explicit reverse saturation current density (J0). Finally, we evaluate precisely the route for approaching theoretical FF in practical solar cell fabrication based on electrical design parameters using the developed model. [ABSTRACT FROM AUTHOR]

The Schockley–Quisser (SQ) limit of 28.64% is distant from the Sb2S3 solar cells' record power conversion efficiency (PCE), which is 8.00%. Such poor efficiency is mostly owing to substantial interface-induced recombination losses caused by defects at the interfaces and misaligned energy levels. The endeavor of this study is to investigate an efficient Sb2S3 solar cell structure via accurate analytical modeling. The proposed model considers different recombination mechanisms such as non-radiative recombination, Sb2S3/CdS interface recombination, Auger, SRH, tunneling-enhanced recombination, and their combined impact on solar cell performance. This model is verified against experimental work (Glass/ITO/CdS/Sb2S3/Au) where a good coincidence is achieved. Several parameters effects such as thickness, doping, electronic affinity, and bandgap are scrutinized. The effect of both bulk traps located in CdS and Sb2S3 on the electrical outputs of the solar cell is analyzed thoroughly. Besides, a deep insight into the effect of interfacial traps on solar cell figures of merits is gained through shedding light into their relation with carriers' minority lifetime, diffusion length, and surface recombination velocity. Our research findings illuminate that the primary contributors to Sb2S3 degradation are interfacial traps and series resistance. Furthermore, achieving optimal band alignment by fine-tuning the electron affinity of CdS to create a Spike-like conformation is crucial for enhancing the immunity of the device versus the interfacial traps. In our study, the optimized solar cell configuration (Glass/ITO/CdS/Sb2S3/Au) demonstrates remarkable performance, including a high short-circuit current (JSC) of 47.9 mA/cm2, an open-circuit voltage (VOC) of 1.16 V, a fill factor (FF) of 54%, and a notable improvement in conversion efficiency by approximately 30% compared to conventional solar cells. Beyond its superior performance, the optimized Sb2S3 solar cell also exhibits enhanced reliability in mitigating interfacial traps at the CdS/Sb2S3 junction. This improved reliability can be attributed to our precise control of band alignment and the fine-tuning of influencing parameters. [ABSTRACT FROM AUTHOR]

Recently, many research efforts have been dedicated to improving light coupling into solar cells and reducing optical losses. Promising candidates regarding scalability include direct nano‐structuring of the absorber layer, anti‐reflective (AR) coatings, or combining both, e.g., pyramidal textures with a conformal coating. However, many of these methods are either insufficient or infeasible for application in thin solar cells. Moreover, approaches based on directly texturing the silicon interface simultaneously strongly increase surface recombination, thus degrading the electronic properties of the solar cell. To circumvent these issues, conformal graded‐index metasurfaces with a correlated positional disorder for light trapping in solar cells are proposed and experimentally demonstrated in this contribution. When considered as a part of a prototypical solar cell geometry, a broadband reduction in reflection is observed that results in photocurrent enhancement. The combined consideration of disorder and conformal graded‐index layers outperforms structures containing only one of these components. The computational guidance toward optimized designs promises to adjust the framework to other settings. The possibility for large‐scale fabrication of the samples paves the way toward a future generation of supporting photonic structures in solar cells. [ABSTRACT FROM AUTHOR]

Surface recombination in an oxygen DC glow discharge in a Pyrex (borosilicate glass) tube is studied via mesoscopic modelling and comparison with measurements of recombination probability. A total of 106 experimental conditions are assessed, with discharge current varying between 10 and 40 mA, pressure values ranging between 0.75 and 10 Torr, and fixed outer wall temperatures ( T w ) of −20, 5, 25 and 50 ∘ C . The model includes O+O and O+O2 surface recombination reactions and a T w dependent desorption frequency. The model is validated for all the 106 studied conditions and intends to have predictive capabilities. The analysis of the simulation results highlights that for T w = − 20 ∘ C and T w = 5 ∘ C the dominant recombination mechanisms involve physisorbed oxygen atoms ( O F ) in Langmuir–Hinshelwood (L-H) recombination O F + O F and in Eley–Rideal (E-R) recombination O 2 + O F , while for T w = 25 ∘ C and T w = 50 ∘ C processes involving chemisorbed oxygen atoms ( O S ) in E-R O + O S and L-H O F + O S also play a relevant role. A discussion is taken on the relevant recombination mechanisms and on ozone wall production, with relevance for higher pressure regimes. [ABSTRACT FROM AUTHOR]

It has been well documented that the usage of a textured cover layer reduces reflection from the air‐solar cell interface, which ultimately enhances the power conversion efficiency (PCE) of a solar cell. The most commonly used patterns, such as pyramids, micropillars, nanowires (NW), and nanoholes have been widely studied and optimized. Besides using such NWs to enhance light absorption, this work also additionally considers the concept of mimicking the antireflection coating of single or multiple layers in minimizing the reflectance and thus enhancing the total absorptance further. It is shown here that at least one order of magnitude shorter multilayer NW pattern of 268 nm total height can outperform a standard NW of 4270 nm height, which needs less material and can also be fabricated at a reduced cost. Furthermore, the proposed design with reduced height has a significantly lower surface‐to‐volume ratio, which also reduces surface recombination loss than the other textured surface patterns. The results presented in this work have been comprehensively analyzed by initially optimizing optical absorption and then completing the electrical simulations. The optimized design in conjunction with a back reflector offers an efficiency as high as 16.434%. [ABSTRACT FROM AUTHOR]

Interfacial passivation plays a pivotal role in achieving efficient and stable perovskite solar cells. Meanwhile, the introduction of 2D perovskites has also been widely reported to be beneficial for enhancing the performance and stability of devices. Herein, DEAI is used as an ammonium salt, which is spin coated onto the surface of the perovskite film, resulting in the formation of a 2D perovskite phase. This alteration increases the film's hydrophobicity, holding the promise of enhancing its humidity stability. Furthermore, DEAI effectively reduces trap density in the perovskite layer, suppressing nonradiative recombination and optimizing the surface potential, thereby improving the efficiency of devices. As a result, the inverted perovskite devices passivated with DEAI achieve a champion power conversion efficiency of 24.26%. Additionally, the unencapsulated DEAI‐passivated perovskite solar cells demonstrate enhanced stability. [ABSTRACT FROM AUTHOR]

Wide bandgap semiconductor-based photocatalysts are usually limited by their low solar energy conversion efficiency due to their limited absorption solar wavelength, their rapid surface recombination of the photogenerated electron–hole pairs, and their low charge-carrier mobility. Here, we report a novel stepwise solution synthesis for achieving a new photocatalytic core–shell consisting of a titanate nanowire/reduced graphene oxide shell (or titanate/rGO) 1D-nanocomposite. The new core–shell nanocomposite maximized the specific surface area, largely reduced the charge transfer resistance and reaction energy barrier, and significantly improved the absorption of visible light. The core–shell nanocomposites' large on/off current ratio and rapid photo-responses boosted the photocurrent by 30.0%, the photocatalysis rate by 50.0%, and the specific surface area by 16.4% when compared with the results for the pure titanate nanowire core. Our numerical simulations support the effective charge separation on the new core–shell nanostructure, which can help further advance the novel photocatalysis. [ABSTRACT FROM AUTHOR]

CuBi2O4 is one of the most studied potential candidates for photoelectrocatalytic solar fuel generation, from H2 production, to CO2 reduction, or even N2 fixation. Hence, understanding its performance and catalytic behavior is key to use this material under real working conditions. Herein, Ag nanocorals are successfully deposited over CuBi2O4 photocathodes for enhancing its performance as a promising candidate for photoelectrocatalytic reduction reactions. An in‐depth study of this novel structure through a combination of several materials' characterization techniques, confirming the tetragonal structure and the stoichiometric proportion of the elemental components, is presented. In addition, the different charge transfer processes and catalytic mechanisms behind the performance of Ag‐decorated CuBi2O4 photocathodes are unveiled through a combination of electrochemical impedance spectroscopy and transient absorption spectroscopy. The combination of these advanced spectroscopies reveals that Ag is acts as a true catalyst, enhancing the charge extraction and decreasing the charge accumulation and the recombination at the CuBi2O4 surface, thus boosting the photocathode performance. [ABSTRACT FROM AUTHOR]

The formula for the voltage noise spectrum due to generation–recombination (G–R) rate fluctuations is derived for uniformly doped majority-carrier n-type semiconductor samples with contacts of finite surface recombination velocities. In the derivation of the formula, a new boundary condition with finite surface recombination velocities considered is used instead of the ohmic boundary condition. The G–R voltage noise spectra are calculated to become saturated and equal in the high electric field region irrespective of surface recombination velocities. However, the behaviors of slow surface recombination velocities in the low electric field region differ from those of fast ones. The profiles of the electron density fluctuations of slow ones differ significantly from those of fast ones in the low-field region. In the high field region, a steep rise in the magnitude of the electron density fluctuation occurs near the voltage contact toward which electrons drift. The various location dependencies of the contribution of noise sources to the voltage power spectral density are also derived for low and high field regions as well as low and high surface recombination velocities, and analytical expressions are developed for the voltage power spectral densities and electron density fluctuations. [ABSTRACT FROM AUTHOR]

The dynamics of H atom recombination on materials of interest for a EUV lithographer was studied under a long-term low-pressure H2 plasma exposure. The similarity of the experimental plasma with the typical EUV-induced plasma over the multilayer mirrors surface of the EUV lithographic machine is demonstrated by means of 2D PIC MC simulation. The measurement of the temporal dynamics of the H atom surface loss probability (γH) is chosen for testing the surface modification during the treatment. Time-resolved actinometry of H atoms with Kr as the actinometer gas was used to detect the dynamics of the H-atom loss probability on the surface of Al, Ru, RVS, and SiO2. It is demonstrated that significant changes of the materials surface occur only at the very beginning of the treatment and are due to surface heating and cleaning effects. After that no changes in the γH are found, indicating that the surface stays absolutely stable. A special test of sensitivity of the used method to the state of surface was carried out. Dynamics of the γH changes with small O2 addition clearly demonstrate modification of the Al surface due to oxidation with the next removal of oxygen by the H2 plasma treatment. The rate of oxide removal is shown to be determined by plasma parameters such as the ion energy and flux to the surface. [ABSTRACT FROM AUTHOR]

A wet chemical synthesis of a novel 2D/3D hierarchical Z-scheme that utilizes manganese oxide decorated 2D Ti 3 C 2 MXene (MnO 2 @MXene), which is designed for effective utilization in environmentally sustainable applications, is presented in this study. The synergistic role of 20 nm thick MnO 2 nanopetals (NPTs) and MXene sheets, which inhibited the electron/hole pair recombination and improved the surface activity, enhanced the catalytic properties of the material. This was facilitated by the unique 3D/2D structural characteristics of MnO 2 NPTs and MXene. The MnO 2 nanopetals NPTs integrated the MXene-based photocatalyst, which was synthesized using the ultrasonication approach, removed ∼99 % of the methylene blue dye (MB) and 75 % of the phenol within 30 min. The antibacterial test of the as-prepared MnO 2 @MXene simultaneously confirmed its admirable antibacterial efficacy. The recyclability test verified that the synthesized material can be recycled multiple times without a significant loss, which was only a 3 % loss in this case, in photocatalytic activity. The results imply that MnO 2 @MXene has significant promise as an eco-friendly material that is suitable for utilization in photocatalytic and antibacterial applications. [ABSTRACT FROM AUTHOR]

A supramolecular photovoltaic strategy is applied to enhance power conversion efficiencies (PCE) of photoelectrochemical devices by suppressing electron–hole recombination after photoinduced electron transfer (PET). Here, the author exploit supramolecular localization of the redox mediator—in close proximity to the dye—through a rotaxane topology, reducing electron–hole recombination in p‐type dye‐sensitized solar cells (p‐DSSCs). Dye PRotaxane features 1,5‐dioxynaphthalene recognition sites (DNP‐arms) with a mechanically‐interlocked macrocyclic redox mediator naphthalene diimide macrocycle (3‐NDI‐ring), stoppering synthetically via click chemistry. The control molecule PStopper has stoppered DNP‐arms, preventing rotaxane formation with the 3‐NDI‐ring. Transient absorption and time‐resolved fluorescence spectroscopy studies show ultrafast (211 ± 7 fs and 2.92 ± 0.05 ps) PET from the dye‐moiety of PRotaxane to its mechanically interlocked 3‐NDI‐ring‐acceptor, slowing down the electron–hole recombination on NiO surfaces compared to the analogue. p‐DSSCs employing PRotaxane (PCE = 0.07%) demonstrate a 30% PCE increase compared to PStopper (PCE = 0.05%) devices, combining enhancements in both open‐circuit voltages (VOC = 0.43 vs 0.36 V) and short‐circuit photocurrent density (JSC = −0.39 vs −0.34 mA cm−2). Electrochemical impedance spectroscopy shows that PRotaxane devices exhibit hole lifetimes (τh) approaching 1 s, a 16‐fold improvement compared to traditional I−/I3−‐based systems (τh = 50 ms), demonstrating the benefits obtained upon nanoengineering of interfacial dye‐regeneration at the photocathode. [ABSTRACT FROM AUTHOR]

Perovskite solar cell (pero‐SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO2 electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero‐SCs, yet still suffers from surface defects of SnO2 nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH4)2CrO4 on the SnO2 ETL. The LOE strategy builds up plentiful nano‐heterojunctions of p‐Cr2O3/n‐SnO2 and the nano‐heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non‐radiative recombination and voltage loss of the pero‐SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero‐SCs based on α‐FAPbI3 with the SnO2 ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T90>700 h. This work provides a brand‐new view for defect modification of SnO2 electron transport layer. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BVO) is regarded as an exceptional photoanode material for photoelectrochemical (PEC) water splitting, but it is restricted by the severe photocorrosion and slow water oxidation kinetics. Herein, a synergistic strategy combined with a Co3(HPO4)2(OH)2 (CoPH) cocatalyst and an Al2O3 (ALO) passivation layer was proposed for enhanced PEC performance. The CoPH/ALO/BVO photoanode exhibits an impressive photocurrent density of 4.9 mA cm−2 at 1.23 VRHE and an applied bias photon-to-current efficiency (ABPE) of 1.47% at 0.76 VRHE. This outstanding PEC performance can be ascribed to the suppressed surface charge recombination, facilitated interfacial charge transfer, and accelerated water oxidation kinetics with the introduction of the CoPH cocatalyst and ALO passivation layer. This work provides a novel and synergistic approach to design an efficient and stable photoanode for PEC applications by combining an oxygen evolution cocatalyst and a passivation layer. [ABSTRACT FROM AUTHOR]

Ultrahigh‐strength steel (UHSS) structures are plated with Zn–Ni coatings because of their excellent corrosion resistance properties, but the plating process is accompanied by the production of hydrogen. The presence of hydrogen in steel results in hydrogen embrittlement. Hence, during the production of UHSS parts, dedicated outgassing steps are employed to remove the diffusible hydrogen from the steel. In a production environment, the real effect of the outgassing process and the outgassing efficiency is unknown for parts coated with Zn–Ni. Hence, a finite element model is developed to capture the evolution of the hydrogen concentration profile in coated UHSS parts during outgassing to study the influence of coating morphology and microstructural features of steel. In order to develop the geometry of the model, scanning electron microscope images are analyzed to understand the microstructure and morphology of the coating. Numerical samples are generated by combining different coating morphologies with steel substrates of varying microstructural features to attain a series of samples with varying features. The results of the outgassing simulations clearly demonstrate the major role of the coating morphology on the hydrogen flux. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are carried out for calculating the surface loss probabilities of neutral species from an argon–methane plasma. These probabilities are the sum of the sticking and surface recombination probabilities. This study considers both the formation of reactive and nonreactive volatile species for evaluating recombination probabilities. Results show that stable species are reflected when hydrocarbon film starts growing on the surface. CH3 is mainly lost by surface recombination leading to the formation of volatile products while very little contributes to film growth. C2H has surface loss probability in agreement with the literature. While C2H loss is usually attributed to sticking on the surface, our results show that its main loss process is due to surface recombination. [ABSTRACT FROM AUTHOR]

Heterojunction perovskite solar cells combine the stability of 2D perovskites and the high efficiency of 3D perovskites, making them an excellent photovoltaic candidate. While heterojunctions with intermixed or gradient perovskites can reduce surface recombination, the aggregation and phase distribution of 2D perovskite induce transport losses, thereby limiting device fill factors. Accordingly, a bulk in situ reconstruction (BISR) strategy is proposed to induce the reconstruction of 3D perovskites on a minim self‐assembled 2D crystal seed, forming heterojunction perovskite that runs through the entire active layer. This facilitates charge extraction, relieves tensile stress, and avoids the decomposition of perovskite on grain boundaries. As a result, the best‐performing heterojunction perovskite solar cells show a high‐power conversion efficiency (PCE) of 24.06% with 82.9% FF for the small‐area device (0.105 cm2) and a superior PCE of 19.2% for the large‐area module (5 × 5 cm2). Importantly, the unencapsulated device shows dramatically improved operational stability, maintaining 87% of its initial efficiency after 8000 h of storage under ambient atmosphere at room temperature. This work provides an effective and simple approach to establish heterojunction perovskite to simultaneously boost the efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Regulating the interfacial charge transfer behavior between cocatalysts and semiconductors remains a critical challenge for attaining efficient photoelectrochemical water oxidation reactions. Herein, using bismuth vanadate (BiVO4) photoanode as a model, it introduces an Au binding bridge as holes transfer channels onto the surfaces of BiVO4, and the cyano‐functionalized cobalt cubane (Co4O4) molecules are preferentially immobilized on the Au bridge due to the strong adsorption of cyano groups with Au nanoparticles. This orchestrated arrangement facilitates the seamless transfer of photogenerated holes from BiVO4 to Co4O4 molecules, forming an orderly charge transfer pathway connecting the light‐absorbing layer to reactive sites. An exciting photocurrent density of 5.06 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (3.4 times that of BiVO4) is obtained by the Co4O4@Au(A)/BiVO4 photoanode, where the surface charge recombination is almost completely suppressed accompanied by a surface charge transfer efficiency over 95%. This work represents a promising strategy for accelerating interfacial charge transfer and achieving efficient photoelectrochemical water oxidation reaction. [ABSTRACT FROM AUTHOR]

The surface oxygen evolution reaction (OER) is severely restricted owing to the sluggish OER kinetics and limited number of reactive sites. Although surface reconstruction can introduce defects to improve the OER performance, they often function as recombination centers and cause severe carrier recombination. With the aid of ultrasonication, the CdIn2S4 photoanode surface is reconstructed using Zn‐modified Cd defects without extreme chemical reaction environment. Owing to the surface reconstruction, the formed type‐II band structure is beneficial for separating photogenerated carriers and reduced the bulk recombination. Additionally, the Zn‐modified Cd defects are introduced in situ during the ultrasound cavitation process, which facilitated the carrier transfer, reduced the surface recombination, and increased the number of surface active sites. First‐principles calculations indicate that the modified Cd defects effectively lower the electrochemical reaction barrier and promote the surface OER kinetics by precisely regulating the four‐electron reaction. Consequently, the optimized photoanode exhibits a enhanced photocurrent of 5.30 mA cm−2 at 1.23 V versus reversible hydrogen electrode. These results demonstrate that an accurate surface reconstruction design can be achieved for introducing and modifying metal defects to improve the transfer and transport behaviors of photogenerated carriers. [ABSTRACT FROM AUTHOR]

Flexible ultraviolet (UV) photodetector exhibits a promising application in portable electronic gadgets, display devices and biomedical imaging. In this study, a flexible photoanode of the photoelectrochemical (PEC)-type UV photodetector based on rutile TiO2 nanowires (TiO2 NWs) grown on carbon fiber cloth is realized. In photovoltaic applications, an insulating layer is usually introduced to suppress interfacial recombination and reduce the surface trap states. The interfacial recombination of semiconductor/electrolyte is suppressed by coating an Al2O3 barrier layer on the TiO2 NWs. The photodetectors of the TiO2@Al2O3 NWs show stable photocurrent, a high light/dark current ratio (I light/ I dark) of 1170, a faster rise and decay response times of 0.09 and 0.09 s, and excellent spectral selectivity from 300 to 400 nm. The peak responsivity of the photodetectors reaches 2.8 mA W−1 at 360 nm. This flexible photoanode have a potential application in wearable PEC UV photodetector. [ABSTRACT FROM AUTHOR]

Efficiently passivating germanium (Ge) surfaces is crucial to reduce the unwanted recombination current in high-performance devices. Chemical surface cleaning is critical to remove surface contaminants and Ge oxides, ensuring effective surface passivation after dielectric deposition. However, Ge oxides can rapidly regrow upon air exposure. To understand the surface evolution after wet cleaning, we present a comprehensive study comparing HF and HCl deoxidation steps on p-type Ge surfaces and monitor the surface as a function of air exposure time. Distinct oxide regrowth dynamics are observed: HF-treated samples exhibit swift regrowth of all Ge oxide states, whereas HCl-treated Ge surfaces exhibit a lower concentration of low degrees of oxidation and slower or no regrowth of high oxide states even after 110 min of air exposure. In addition, the presence of Ge–Cl bonds induces different oxidation dynamics compared to the Ge–OH bonds resulting from HF cleaning. This leads to varying surface electronic band structures, with HF-treated Ge exhibiting a strong positive band bending (+ 0.20 eV). Conversely, HCl-treated samples display a lower band curvature (+ 0.07 eV), mostly due to the presence of Ge–Cl bonds on the Ge surface. During air exposure, the increased GeO x coverage significantly reduces the band bending after HF, while a constant band bending is observed after HCl. Finally, these factors induce a reduction in the surface recombination velocity after wet etching. Combining both chemical and field-induced passivation, HF-treated Ge without rinsing exceeds 800 μ s. [ABSTRACT FROM AUTHOR]

Background. he dependences of the light intensity on time and the photocurrent flowing in the resistor are generally described by various functions. Methods have been studied for obtaining the time dependence of the intensity of light pulses of arbitrary shape, following with a frequency ω, from the time dependence of the photocurrent in the presence of recombination of charge carriers on the surface of the semiconductor. Materials and methods. The results were obtained based on a study of the kinetics of photoconductivity of a resistor for linear and quadratic recombination laws in the bulk of a semiconductor. The diffusion of nonequilibrium charge carriers to the surfaces of the photoresistor with their subsequent surface recombination is taken into account. The first method is based on the use of the photocurrent differentiation operation. The second method allows you to restore the intensity of an optical pulse of an arbitrary shape from the amplitudes of the harmonics of the expansion of the function that specifies the dependence of the current on time in a Fourier series. Results and conclusions. Nonlinear, frequency and phase distortions in the region of high frequencies are small. The proposed methods are valid when the inequality ωτ≥1 (τ is the effective lifetime of the main charge carriers) is fulfilled.

The interest in germanium (Ge) is rising for use in field-effect transistors, (space) photovoltaics, and silicon photonics. Suppressing and understanding carrier recombination at the Ge surface are vital for the performance of Ge in these applications. In this work, we have investigated the surface recombination at various germanium–dielectric interfaces (Ge/Al2O3, Ge/SiNx, Ge/GeOx/Al2O3, and Ge/a-Si:H/Al2O3). For this purpose, we performed corona-lifetime experiments and extracted a set of recombination parameters by fitting the data with the theoretical Girisch model. To keep the model straightforward, the distributions of the capture cross sections and the interface defect density (D i t) were parameterized. The importance of each parameter in these distributions was examined so that a minimum number of parameters was distilled: the so-called fundamental recombination velocities (S p 0 and S n 0 ) and the magnitude of the D i t near the valence and conduction band edge (D it , VB and D it , CB ). These parameters form together with the fixed charge density (Q f) , the spatial distribution thereof (σ Q) , and a minimum surface recombination velocity (S min ) , a set of parameters that can well describe our experimental data. Relevant insights were obtained from the experiments, with highlights including a Ge/GeOx/Al2O3 stack with virtually no fixed charge density, a highly passivating Ge/a-Si:H/Al2O3 stack, and a negatively charged Ge/SiNx stack. The findings in this study are valuable for applications where a more profound understanding of recombination at Ge surfaces is of concern, such as in photonics, photovoltaics, and nano-electronics. [ABSTRACT FROM AUTHOR]

Sidewall passivation using atomic layer deposition (ALD) can efficiently improve external quantum efficiency (EQE). Such treatment increases EQE, a combination of internal quantum efficiency (IQE) and light extraction efficiency (LEE), primarily by curtailing surface recombination according to the ABC model. Determined by the ratio of radiative recombination rate to total recombination rate, the IQE of an LED holds a significant correlation with the diode's ideality factor in the Shockley model. In this paper, we analysis the mechanism of ALD sidewall passivation enhancing device performance in detail from the aspects of electrical performance improvement and optical performance improvement. [ABSTRACT FROM AUTHOR]

The surface recombination velocity (SRV), which reflects the fundamental characteristics of surface defects of semiconductor wafers, is an important parameter in evaluating the quality of surface passivation and electrical performance of surface devices. In conventional photocarrier radiometry (PCR) used for characterizing the electronic transport properties of electronically thick silicon wafers, the rear SRV usually cannot be determined directly due to the relatively low sensitivity of PCR signal to the rear SRV. On the other hand, the determination of front SRV is also very sensitive to the experimental measurement error, especially the measurement error of instrumental frequency response, which is not always easy to be accurately measured in the experiment. In this paper, the front and rear SRVs of silicon wafers are extracted simultaneously with high accuracy by a differential PCR via multi-parameter fitting of the experimental frequency dependences of amplitude ratio and phase difference of PCR signals obtained from the regular measurements and measurements with wafers being flipped respectively to a corresponding differential nonlinear PCR model. The comparison between the front and rear SRVs determined by the conventional and differential PCRs indicates that the differential PCR is highly accurate for the simultaneous determination of the front and rear SRVs of silicon wafers. [ABSTRACT FROM AUTHOR]