Carrier Recombination Centers Research Articles

Understanding Defects in Perovskite Solar Cells through Computation: Current Knowledge and Future Challenge.

Lead halide perovskites with superior optoelectrical properties are emerging as a class of excellent materials for applications in solar cells and light-emitting devices. However, perovskite films often exhibit abundant intrinsic defects, which can limit the efficiency of perovskite-based optoelectronic devices by acting as carrier recombination centers. Thus, an understanding of defect chemistry in lead halide perovskites assumes a prominent role in further advancing the exploitation of perovskites, which, to a large extent, is performed by relying on first-principles calculations. However, the complex defect structure, strong anharmonicity, and soft lattice of lead halide perovskites pose challenges to defect studies. In this perspective, on the basis of briefly reviewing the current knowledge concerning computational studies on defects, this work concentrates on addressing the unsolved problems and proposing possible research directions in future. This perspective particularly emphasizes the indispensability of developing advanced approaches for deeply understanding the nature of defects and conducting data-driven defect research for designing reasonable strategies to further improve the performance of perovskite applications. Finally, this work highlights that theoretical studies should pay more attention to establishing close and clear links with experimental investigations to provide useful insights to the scientific and industrial communities.

Electron-Phonon Coupling-Mediated Ultralong Carrier Lifetime in an All-Inorganic Two-Dimensional Cs2PbI2Cl2 Perovskite: Explanation for the High Antisite Defect Tolerance.

Two-dimensional (2D) halide perovskite are appealing candidates for applications in optoelectronics and photovoltaics, but their energy conversion efficiency is severely limited by nonradiative electron-hole recombination. In most investigations, point defects with deep defect levels and deep charge-state transition levels in the band gap are treated as the carrier recombination centers. For the all-inorganic 2D Css 2PbI2Cl2, the IPb antisite defect is the most likely to form and cause nonradiative electron-hole recombination. By using density functional theory and ab initio nonradiative molecular dynamics calculations, we found that the IPb defect can introduce the deep acceptor and donor levels into the band gap. Because electron-phonon coupling gives rise to weak nonadiabatic coupling and rapid loss of electronic coherence, those levels lead to a reduction of the carrier loss and the prolongation of the excited-state carrier lifetime, thereby enhancing the photoelectric and defect tolerance properties of the Cs2PbI2Cl2 material. These results could deepen the understanding of the chemistry of defects and carrier dynamics in perovskite materials.

The Role of Grain Boundaries in Organic–Inorganic Hybrid Perovskite Solar Cells and its Current Enhancement Strategies: A Review

Grain boundaries (GBs) in perovskite polycrystalline films are the most sensitive place for the formation of the defect states and the accumulation of impurities. Thus, abundant works have been carried out to explore their properties and then try to solve the induced problems. Currently, two important issues remain. First, the role of GBs in charge carrier dynamics is unclear due to their component complexity/defect tolerance nature and the insufficiency in testing accuracy. Some works conclude that GBs are benign, while others consider GBs as carrier recombination centers. Things for sure are the deterioration in ion transport and perovskite decomposition. Second, to solve the known hazards of GBs, a lot of additives have been added to anchoring ions and passivate defects. But in most of those works, GBs and perovskite surfaces are treated in the same manner ignoring the fact that GB is essentially a homogeneous junction in a narrow and slender space, while surface is a heterogeneous junction with a stratified structure. In this review, we focus on works insight into GBs and additives for them. Additionally, we also discuss the prospects of the maturity of GB exploration toward upscaling the manufacture of perovskite photovoltaic and related optoelectronic devices.

Molten salt-assisted anti-defect engineering to tailor ordered, highly crystalline g-C3N4 nanorods for efficient photocatalytic H2O2 production

Graphite carbon nitride (g-C3N4) is widely recognized as one of the most popular catalysts for photocatalytic hydrogen peroxide (H2O2) production. However, it is often overlooked that general g-C3N4 materials contain numerous dangling bonds and defects, which serve as recombination centers for photogenerated carriers and significantly hinder their catalytic activity. Herein, we present a novel approach to address this issue by rationally tailoring well-ordered g-C3N4 nanorods (CNR) through molten salt-assisted anti-defect engineering. The resulting highly crystalline CNR demonstrates high efficiency in the artificial photosynthesis of H2O2. Experimental results indicate that enhancing the crystallinity of g-C3N4 while reducing the defect concentration effectively promotes charge separation and transport. As a result, it exhibits a remarkable H2O2 generation rate of 1.58 mmol g-1h−1 using air as the oxygen source, accompanied by an apparent quantum yield of 18.00 % (λ = 400 nm). The excellent photocatalytic performance of CNR surpasses that of all previously reported pristine g-C3N4 materials. This work sheds light on the effectiveness of molten salt-assisted anti-defect engineering in improving catalyst activity, with potential applications in solar cells, sensor devices and other catalytic systems.

Extraordinary photooxidation properties of ZnO nanosheets with surface oxygen vacancies of low density

Surface defect engineering strategies are critical for catalytic activity, especially in the photodegradation of organic pollutants. However, the exact function of the oxygen vacancies for the photooxidation performance of ZnO is unclear. Oxygen vacancies might act as electron donors to encourage carrier separation and then boost catalytic efficiency; besides, excessive oxygen vacancies might act as recombination centers for photogenerated electron–hole, which impairs photocatalytic performance. Therefore, the specific effect of the amount of oxygen vacancies in ZnO needs to be investigated. We developed a facile method, which is inspired by the aforementioned strategy, to adjust the amount of oxygen vacancies in ZnO nanosheets for exploring its photocatalytic activity. ZnO nanosheets with oxygen vacancies of low density exhibit a greatly enhanced photooxidation ability and can rapidly and stably degrade high concentration (4 × 10−4 mol/L) of phenol compared with nearly inactivity of the ZnO nanosheets with plentiful oxygen vacancies. This mechanism of the improved photocatalytic activity is proposed to be mainly due to the significant reduction in oxygen vacancies as carrier recombination centers and the increase in photogenerated electron–hole mobility. This research presents a new idea for the surface defect engineering design of regulated photocatalysts to enhance photocatalytic activity.

Electronic structure engineering of BaTiO3 cuboctahedrons by doping copper to enhance the photocatalytic activity for environmental remediation

The advent of perovskites as an efficient photocatalyst has paved the way to newer possibilities in the degradation of contaminants such as dyes and toxic heavy metal ions. The alleged poor photocatalyst BaTiO3 was engineered to perform better by decreasing its bandgap to make it visible light active via doping. The high-risk factor in the reduction of the bandgap is the formation of recombination centers for the charge carriers which decreases the efficiency of the photocatalyst. Herein, we studied the electronic structure tuning of BaTiO3 by doping copper and developed a one pot synthesis method to obtain copper doped BaTiO3 that has a high surface area, lower recombination rate, and higher photocatalytic efficiency towards dye degradation and hexavalent chromium ion reduction. The 0.5 CuBT sample had a photocatalytic efficiency of 99.4 % for methyl violet decomposition within 120 min and 99.8 % for hexavalent chromium ion reduction by fructose in 20 min.

TiO2 nanotube arrays as a photoelctrochemical platform for sensitive Ag+ ion detection based on a chemical replacement reaction

Silver ions (Ag+) are essential for living organisms; however, they are toxic at high concentrations. Herein, a photoelectrochemical (PEC) platform is constructed using TiO2 nanotube arrays (TiNTs) prepared by electrochemical anodization of electrode substrate, with high photocurrent response in visible-light region by coating PbS nanocrystals (NCs) through continuous chemical bath deposition (CBD) technique. Combining the low band-gap of PbS with the improved photogenerated electron-hole separation at PbS/TiO2 heterojunctions, the resulting PbS/TiNTs electrode possesses a highly improved PEC response under visible light. Owing to an efficient chemical replacement of Pb(II) in PbS by targeted Ag+ ions, the formed Ag2S components become the new recombination centers for charge carriers, leading to decreased PEC response. Based on photocurrent reduction, the PEC electrode demonstrated an excellent sensing ability for trace Ag+ in solution with a linear range of 5.0 × 10−3 ∼ 5.0 × 10−8 mol L−1 and a limit of detection reaching 1.5 × 10−8 M (S/N = 3). The semiconductor hybrid nanotubes-based photoelectrochemical platform provides a promising route to design highly sensitive and selective sensors for directly detecting ions or molecules.

Study of flexible packing and stability of GaInP/GaAs solar cells

Flexible III-V thin-film solar cells are usually used as space power supply in spacecrafts. In practical applications, suitable encapsulated materials can protect the cells from being affected by environmental factors such as moisture, oxidation and pollutants. Therefore, it is critical to explore suitable flexible encapsulation schemes and long-term stability of solar cell performance. In this paper, the prepared flexible GaInP/GaAs solar cells are welded by resistance welding, and then laminated with polymer encapsulation thin films and hot melt adhesives with high light transmission. After being encapsulated, the flexible two-junction solar cell achieves good electrical performance (<i>J</i><sub>sc</sub> = 13.105 mA·cm<sup>–2</sup>, <i>V</i><sub>oc</sub> = 2.360 V), the photoelectric conversion efficiency can reach 24.81%, and the weight density is about 405 g/m<sup>2</sup>. The performance stability and environmental tolerance of the encapsulated flexible GaInP/GaAs solar cells under complex storage conditions are investigated. The results show that the encapsulated flexible solar cells still maintain good stability after 85 ℃/85% RH damp heat has been tested for more than 1000 h and 108 cycles of thermal cycling test between –60 ℃ and 75 ℃, respectively. It also proves that the encapsulated technology adopted in this experiment is feasible and has an excellent protective effect on the double-junction solar cells. However, there is a slight decrease in the open-circuit voltage in the long-term damp heat test (Δ<i>V</i><sub>oc</sub> ≈ 0.023 V), which may reflect the change of the solar cell itself. By further extracting the changes of the ideal factors <i>n</i><sub>1</sub> and <i>n</i><sub>2</sub> representing the recombination mechanism and diffusion mechanism respectively from the dark <i>I</i>-<i>V</i> curves (Δ<i>n</i><sub>1</sub> = 1.295, Δ<i>n</i><sub>2</sub> = 0.087), it can be found that the slight drop of open-circuit voltage is closely related to the recombination enhancement (Δ<i>n</i><sub>1</sub><inline-formula><tex-math id="Z-20230621123129">\begin{document}$\gg $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20230352_Z-20230621123129.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20230352_Z-20230621123129.png"/></alternatives></inline-formula>Δ<i>n</i><sub>2</sub>). In the long-term high temperature and humidity environment, it is easy to introduce defects in the material of the solar cells, serving as the carrier recombination centers, thus accelerating the carrier recombination, reducing the parallel resistance, shortening the minority carrier lifetime, and increasing the reverse saturation current resulting in a slight drop in the open-circuit voltage. In addition, the electrical simulation results based on the diode-model indicate that the change in the performance of the solar cells after flexible encapsulation is due to the enhanced carrier recombination under damp heat test, which reduces the open-circuit voltage.

Activation of 2D titanate nanosheet photocatalysts by nitrogen doping and solution plasma processing.

Novel two-dimensional (2D) oxides are of great interest for photocatalysis because of their superlative physical features, namely, large surface areas, short charge diffusion pathways, high crystallinity and easy surface modification. However, most 2D oxides suffer from weak visible light absorption and severe photogenerated carrier recombination. Nitrogen doping can successfully narrow the bandgap of 2D oxides but can hardly improve the charge separation. In this work, we pre-dope nitrogen into 2D titanate nanosheets (HTiO), followed by surface processing with solution plasma. By dual modification of nitrogen doping and solution plasma processing (SPP), the modified 2D titanate nanosheets (N-HTiO-SPP) display broad absorption extending to the visible light region and the healing of oxygen vacancies brought about by nitrogen doping. Compared with HTiO and nitrogen doped titanate (N-HTiO), a higher removal rate and mineralization rate towards the photocatalytic degradation of acetaldehyde were achieved over N-HTiO-SPP under solar light. This work provides a powerful way to activate 2D wide bandgap semiconductors for enhanced photocatalytic activity.

Vacancy-Regulated Charge Carrier Dynamics and Suppressed Nonradiative Recombination in Two-Dimensional ReX2 (X = S, Se).

Point defects in semiconductors usually act as nonradiative charge carrier recombination centers, which severely limit the performance of optoelectronic devices. In this work, by combining time-domain density functional theory with nonadiabatic molecular dynamics simulations, we demonstrate suppressed nonradiative charge carrier recombination and prolonged carrier lifetime in two-dimensional (2D) ReX2 (X = S, Se) with S/Se vacancies. In particular, a S vacancy introduces a shallow hole trap state in ReS2, while a Se vacancy introduces both hole and electron trap states in ReSe2. Photoexcited electrons and holes can be rapidly captured by these defect states, while the release process is slow, which contributes to an elongated photocarrier lifetime. The suppressed charge carrier recombination lies in the vacancy-induced low-frequency phonon modes that weaken electron-phonon coupling, as well as the reduced overlap between electron and hole wave functions that decreases nonadiabatic coupling. This work provides physical insights into the charge carrier dynamics of 2D ReX2, which may stimulate considerable interest in using defect engineering for future optoelectronic nanodevices.

Surface nanopatterning of amorphous gallium oxide thin film for enhanced solar-blind photodetection

Gallium oxide is an ultra-wide band gap semiconductor (E g > 4.4 eV), best suited intrinsically for the fabrication of solar-blind photodetectors. Apart from its crystalline phases, amorphous Ga2O3 based solar-blind photodetector offer simple and facile growth without the hassle of lattice matching and high temperatures for growth and annealing. However, they often suffer from long response times which hinders any practical use. Herein, we report a simple and cost-effective method to enhance the device performance of amorphous gallium oxide thin film photodetector by nanopatterning the surface using a broad and low energy Ar+ ion beam. The ripples formed on the surface of gallium oxide thin film lead to the formation of anisotropic conduction channels along with an increase in the surface defects. The defects introduced in the system act as recombination centers for the charge carriers bringing about a reduction in the decay time of the devices, even at zero-bias. The fall time of the rippled devices, therefore, reduces, making the devices faster by more than 15 times. This approach of surface modification of gallium oxide provides a one-step, low cost method to enhance the device performance of amorphous thin films which can help in the realization of next-generation optoelectronics.

High-performance self-powered ultraviolet photodetector based on PEDOT:PSS/CuO/ZnO nanorod array sandwich structure

This study reports a sensitive self-powered ultraviolet photodetector (UV PD) fabricated with a facile cost-effective hydrothermal and RF magnetron sputtering combination method. The obtained PD is in sandwich configuration based on p-n junction, consisting of ZnO nanoarray bottom n-layer, poly (3, 4 ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) top p-layer, and CuO insertion layer. The developed PD shows superior self-powered performance with responsivity of 9.96 mA/W under weak UV illumination (365 nm, 0.4 mW/cm2) and good wavelength selectivity (R365nm/R400nm = 4.87 × 102). It is found that the CuO insertion layer plays a vital role in the device performance, proving by the fact that the responsivity of the PD with the interlayer is almost 12 times that of the device without. This can be ascribed to the CuO thin layer which improves the junction quality by reducing the recombination centers for carriers, widening the depletion region and providing stepping energy levels between the band edges of ZnO and PEDOT:PSS, and thereby improves overall collection of the photo-generated carriers, leading to much improved photoresponse. The obtained PD also exhibits great multi-cycle stability. This efficient self-powered UV PD along with its cost-effective fabrication process is promising in UV sensor applications.

Impact of band-engineered polymer-interlayers on heterojunction solar cells based on 2D-layered perovskites (Cs3Sb2ClxI9−x)

Thin-film formation process of Cs3Sb2ClxI9−x perovskite in its 2D layered-form is complex and provides a poor control over film-morphology and results in a rough film-surface. Such a surface prompts formation of recombination centers for photogenerated carriers at the interface between the active and carrier-transport layers. We report a process of interface-engineering to decrease recombination loss and thereby improve photovoltaic parameters. Apart from using an inert polymer layer to improve the surface morphology of Cs3Sb2ClxI9−x thin-films, we have introduced transition metal dichalcogenide (TMD) nanoflakes into the polymer; the hybrid interlayer (polymer:TMD) between the active perovskite layer and an electron-transport layer (ETL) could increase the recombination resistance without affecting the series resistance of devices, leading to an increase in photovoltaic properties. We have employed atomic force microscopy and Kelvin probe force microscopy to probe the perovskite surface. Current-voltage characteristics and impedance spectroscopy of the devices were recorded to derive their recombination and series resistances upon the interface-engineering process. Band-diagram of the devices based on Cs3Sb2ClxI9−x/polymer:TMD/ETL have been drawn from scanning tunneling spectroscopy and differential tunnel conductance thereof. The heterojunction devices with a type-II band-alignment at the interfaces have resulted in an enhanced photovoltaic performance in Cs3Sb2ClxI9−x-based solar cells with a PCE of 3.42%.

Fully Condensed Poly (Triazine Imide) Crystals: Extended π‐Conjugation and Structural Defects for Overall Water Splitting

AbstractConventional polymerization for the synthesis of carbon nitride usually generates amorphous heptazine‐based melon with an abundance of undesired structural defects, which function as charge carrier recombination centers to decrease the photocatalytic efficiency. Herein, a fully condensed poly (triazine imide) crystal with extended π‐conjugation and deficient structure defects was obtained by conducting the polycondensation in a mild molten salt of LiCl/NaCl. The melting point of the binary LiCl/NaCl system is around 550 °C, which substantially restrain the depolymerization of triazine units and extend the π‐conjugation. The optimized polymeric carbon nitride crystal exhibits a high apparent quantum efficiency of 12 % (λ=365 nm) for hydrogen production by one‐step excitation overall water splitting, owing to the efficient exciton dissociation and the subsequent fast transfer of charge carriers.

Fully Condensed Poly (Triazine Imide) Crystals: Extended π‐Conjugation and Structural Defects for Overall Water Splitting

AbstractConventional polymerization for the synthesis of carbon nitride usually generates amorphous heptazine‐based melon with an abundance of undesired structural defects, which function as charge carrier recombination centers to decrease the photocatalytic efficiency. Herein, a fully condensed poly (triazine imide) crystal with extended π‐conjugation and deficient structure defects was obtained by conducting the polycondensation in a mild molten salt of LiCl/NaCl. The melting point of the binary LiCl/NaCl system is around 550 °C, which substantially restrain the depolymerization of triazine units and extend the π‐conjugation. The optimized polymeric carbon nitride crystal exhibits a high apparent quantum efficiency of 12 % (λ=365 nm) for hydrogen production by one‐step excitation overall water splitting, owing to the efficient exciton dissociation and the subsequent fast transfer of charge carriers.

Thin-Film Solar Cells Based on Selenized CuSbS2 Absorber.

Copper antimony sulfide (CuSbS2) has attracted significant interest as an earth-abundant photovoltaic absorber. However, the efficiency of the current CuSbS2 photovoltaic device is too low to meet the requirement of a large-scale application. In this study, selenylation was introduced to optimize the band structure and improve the device performance. Selenized CuSbS2 [CuSbS2(Se)] films were realized using porous CuSbS2 films prepared by spray deposition with a post-treatment in Se vapor. The as-prepared CuSbS2(Se) films exhibited a compact structure. X-ray diffraction and elemental analysis confirmed the effective doping of Se into the lattice by substituting a part of S in CuSbS2. Elemental analysis revealed a gradient distribution for Se from the top surface to the deeper regions, and the substitution rate was very high (>39%). Dark J–V characteristics and AC impedance spectroscopy analysis showed that selenylation significantly reduced the carrier recombination center. As a result, the selenized CuSbS2 device exhibited a significant efficiency improvement from 0.12% to 0.90%, which is much higher than that of the simply annealed device (0.46%), indicating this technique is a promising approach to improve the performance of CuSbS2 solar cells.

Cyano group-enriched crystalline graphitic carbon nitride photocatalyst: Ethyl acetate-induced improved ordered structure and efficient hydrogen-evolution activity

The molten salt-assisted route is one of the most important methods to improve the crystallinity of conventionally disordered bulk graphitic carbon nitride (g-C3N4). However, the residual potassium ions from potassium chloride/lithium chloride molten salt can greatly impact the ordered structure of g-C3N4 and serve as the recombination centers of photoinduced carriers, causing limited photocatalytic hydrogen-evolution performance. In this article, the ethyl acetate-mediated method is first developed to not only further improve the ordered structure of traditional crystalline g-C3N4, but also produce more cyano groups for preparing highly efficient g-C3N4 photocatalysts. Herein, the ethyl acetate can gradually hydrolyze to produce hydrogen ions, which can promote the more ordered sheet-like structure and more cyano groups by effective removal of residual potassium ions in the traditional crystalline g-C3N4, leading to the formation of cyano group-enriched crystalline g-C3N4 photocatalysts (CC-CN). As a result, the resultant CC-CN displays the remarkably enhanced photocatalytic hydrogen-evolution performance (295.30 µmol h−1 with an apparent quantum efficiency about 12.61%), in comparison to the bulk g-C3N4 (14.97 µmol h−1) and traditional crystalline g-C3N4 (24.60 µmol h−1). The great improvement of photocatalytic performance can mainly be ascribed to the synergism of improved ordered structure and abundant cyano groups, namely, the efficient transfer and separation of photoinduced charges as well as excellent interfacial hydrogen-generation reaction, respectively. The present work may deliver new strategies to prepare other high-crystalline photocatalysts with great efficiency.

Recombination and Charge Collection at Nickel Silicide Precipitates in Silicon Studied by Electron Beam‐Induced Current

Nickel di-silicide layers have attracted scientific interest since the 1990’s as lattice-matched Schottky barriers on silicon and as strong carrier recombination centers when embedded in the silicon. High-resolution electron microscopy and electron beam-induced current are used by Philipp Saring and Michael Seibt (article number 2100142) to show that atomically thin silicide precipitates have properties similar to bulk nickel di-silicide in terms of the Schottky barrier height and electric conductivity. The cover image is an artistic view on processes of recombination and charge collection at thin silicide platelets. Experimental data are shown in front of the silicide’s atomic structure in silicon (image courtesy by L. Kroll).

S defect-rich ultrathin 2D MoS2: The role of S point-defects and S stripping-defects in the removal of Cr(VI) via synergistic adsorption and photocatalysis

In the field of photocatalysis, one focus is on high-performance visible light catalysis. For this study, which follows the defect engineering strategy, ultrathin two-dimensional (2D) S defect-rich MoS2 nanosheets were created in situ by ball-milling MoS2 nanosheets with ascorbic acid and then used for the removal of Cr(VI) from wastewater. The results show that ascorbic acid increases both the specific surface area of MoS2 nanosheets and the concentration of S stripping-defects significantly. Of the samples, D-MoS2-3 (i.e., S defect-rich ultrathin 2D MoS2 nanosheets) exhibited the best Cr(VI) adsorption capacity and photocatalytic activity thanks to its large specific surface area and a high concentration of total S defects (18.5%), 311.1% better than for P-MoS2 (i.e., pristine MoS2 nanosheets) (4.5%). The concentration of S point-defects in D-MoS2-3 is only a little greater than in P-MoS2, but the concentration of S stripping-defects is significantly greater. S point-defects at such a high concentration readily act as recombination centers for photogenerated carriers. By contrast, S stripping-defects that lack dangling Mo-S bonds trap photogenerated holes and add to the separation efficiency of photogenerated electron-hole pairs. As a consequence, the photocatalytic performance of D-MoS2-3 in removing Cr(VI) is significantly better. Given this finding, the present study offers a new design pathway and a reference for the practical application of defect engineering to ultrathin 2D materials.

Interfacial Engineering of Cu2O Passivating Contact for Efficient Crystalline Silicon Solar Cells with an Al2O3 Passivation Layer

Passivating contacts that simultaneously promote carrier selectivity and suppress surface recombination are considered as a promising trend in the crystalline silicon (c-Si) photovoltaic industry. In this work, efficient p-type c-Si (p-Si) solar cells with cuprous oxide (Cu2O) hole-selective contacts are demonstrated. The direct p-Si/Cu2O contact leads to a substoichiometric SiOx interlayer and diffusion of Cu into the silicon substrate, which would generate a deep-level impurity behaving as carrier recombination centers. An Al2O3 layer is subsequently employed at the p-Si/Cu2O interface, which not only serves as a passivating and tunneling layer but also suppresses the redox reaction and Cu diffusion at the Si/Cu2O interface. In conjunction with the high work function of Au and the superior optical property of Ag, a power conversion efficiency up to 19.71% is achieved with a p-Si/Al2O3/Cu2O/Au/Ag rear contact. This work provides a strategy for reducing interfacial defects and lowering energy barrier height in passivating contact solar cells.