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Fabrication of halide perovskite (HP) solar cells typically involves the sequential deposition of multiple layers to create a device stack, which is limited by the thermal and chemical incompatibility of top contact layers with the underlying HP semiconductor. One emerging strategy to overcome these restrictions on material selection and processing conditions is lamination, where two half-stacks are independently processed and then diffusion bonded to complete the device. Lamination reduces the processing constraints on the top side of the solar cell to allow new device designs, expanded use of deposition methods, and self-encapsulation of devices. While laminated perovskite solar cells with high efficiencies and novel interlayer combinations have been demonstrated, there is a limited understanding of how the lamination process parameters affect the diffusion-bond quality and material properties of the resulting HP layer. In this study, we systematically vary temperature, pressure, and time during lamination and quantify the resulting impacts on bonded area, grain domain size, and photoluminescence. A design of experiments is performed, and statistical analysis of the experimental results is used to quantitatively evaluate the resulting process–structure–property relationships. The lamination temperature is found to be the key parameter controlling these properties. A temperature of 150 °C enables successful bonding over 95% of the substrate area and also results in increases in apparent grain domain size and photoluminescence intensity. Based on these insights, the lamination temperature of functional perovskite solar cell devices is varied, demonstrating the importance of the resulting bond quality on device performance metrics.

Thin-film photovoltaics (PV) offers a path to decarbonize global energy production. Unfortunately, existing thin-film solar absorbers have major issues associated with either elemental abundance, stability, or performance. Entirely new and disruptive materials platforms are rarely discovered, and their search is traditionally slow and serendipitous. Here, we report a first-principles high-throughput (HT) computational screening for new solar absorbers among 40,000 known inorganic materials. Next to band gap and carrier effective masses, we also use computed intrinsic defects as they can limit the carrier lifetime. We identify the Zintl-phosphide BaCd2P2as a potential high-efficiency solar absorber. Follow-up experiments confirm the promises of BaCd2P2, highlighting an optimal band gap, bright photoluminescence (PL), and long carrier lifetime, even in unoptimized powder samples. Importantly, BaCd2P2contains no critical elements and is stable in air and water. Our work demonstrates how computational screening combined with experiments can accelerate the search for photovoltaic materials.

Transport layer and interface optimization is critical for improving the performance and stability of perovskite solar cells (PSCs) but is restricted by the conventional fabrication approach of sequential layer deposition. While the bottom transport layer is processed with minimum constraints, the narrow thermal and chemical stability window of the halide perovskite (HP) layer severely restricts the choice of top transport layer and its processing conditions. To overcome these limitations, we demonstrate lamination of HPs─where two transport layer-perovskite half-stacks are independently processed and diffusion-bonded at the HP-HP interface─as an alternative fabrication strategy that enables self-encapsulated solar cells. Power conversion efficiencies (PCE) of >21% are realized using cells that incorporate a novel transport layer combination along with dual-interface passivation via self-assembled monolayers, both of which are uniquely enabled by the lamination approach. This is the highest reported PCE for any laminated PSC encapsulated between glass substrates. We further show that this approach expands the processing window beyond traditional fabrication processes and is adaptable for different transport layer compositions. The laminated PSCs retained >75% of their initial PCE after 1000 h of 1-sun illumination at 40 °C in air using an all-inorganic transport layer configuration without additional encapsulation. Furthermore, a laminated 1 cm2device maintained a Vocof 1.16 V. The scalable lamination strategy in this study enables the implementation of new transport layers and interfacial engineering approaches for improving performance and stability.

For a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) film employed in a device stack, charge must pass through both the bulk of the film and interfaces between adjacent layers. Thus, charge transport is governed by both bulk and contact resistances. However, for ultrathin films (e.g., flexible devices, thin-film transistors, printed electronics, solar cells), interfacial properties can dominate over the bulk properties, making contact resistance a significant determinant of device performance. For most device applications, the bulk conductivity of PEDOT:PSS is typically improved by blending additives into the solid film. Doping PEDOT:PSS with secondary dopants (e.g., polar small molecules), in particular, increases the bulk conductivity by inducing a more favorable solid morphology. However, the effects of these morphological changes on the contact resistance (which play a bigger role at smaller length scales) are relatively unstudied. In this work, we use transfer length method (TLM) measurements to decouple the bulk resistance from the contact resistance of PEDOT:PSS films incorporating several common additives. These additives include secondary dopants, a silane crosslinker (typically used to stabilize the PEDOT:PSS film), and multi-walled carbon nanotubes (conductive fillers). Using conductive atomic force microscopy, Kelvin probe force microscopy, Raman spectroscopy, and photoelectron spectroscopy, we connect changes in the contact resistance to changes in the surface morphology and energetics as governed by the blended additives. We find that the contact resistance at the PEDOT:PSS/silver interface can be reduced by (1) increasing the ratio of PEDOT to PSS chains, (2) decreasing the work function, (3) decreasing the benzoid-to-quinoid ratio at the surface of the solid film, (4) increasing the film uniformity and contact area, and (5) increasing the phase-segregated morphology of the solid film.

Water participates in multiple modes of degradation in photovoltaic (PV) modules including encapsulant yellowing, delamination, and contact corrosion. To mitigate moisture-induced degradation, we must understand the kinetics of moisture in state-of-the-art encapsulants and module architectures. In this article, we present a robust optical method to quantify water content in the front and rear side encapsulants of bifacial silicon PV modules, then use such measurements to validate a model for simulating water concentration in these modules. First, we quantify the solubility of water in four modern encapsulants: ethylene vinyl acetate and polyolefin, each with and without UV-blocking additives. Second, we use water reflectometry detection to measure the diffusion of moisture within glass-backsheet modules as a function of time and environmental condition. Third, we present a model of moisture transport in bifacial silicon PV modules and show it to be consistent with our measurements. Crucially, our methodology enables the separate evaluation of water content in the front encapsulant and the rear polymers within glass-backsheet modules. Overall, our work presents a quantitative picture of moisture in emerging module architectures and a framework to extend this approach other encapsulants and module designs.

While halide perovskites attract significant academic attention, examples of industrial production at scale are still sparse. In this perspective, we review practical challenges hindering the commercialization of halide perovskites and discuss how machine-learning (ML) tools could help: (1) active-learning algorithms that blend institutional knowledge and human expertise could help stabilize and rapidly update baseline manufacturing processes, (2) computer-imaging methods with ML-based classification tools could help narrow the performance gap between large- and small-area devices, and (3) inference methods could help accelerate root-cause analysis by reconciling multiple data streams and simulations, focusing research efforts on the highest-probability areas. We conclude that to tackle many of these challenges, incremental—not radical—adaptations of existing ML methods are needed. We propose how industry-academic partnerships could help adapt “ready-now” ML tools to specific industry needs, further improve process control by revealing underlying mechanisms, and develop “gamechanger” discovery-oriented algorithms to better navigate the vast spaces of materials choices.

Moisture ingress is an established issue for photovoltaic module durability. Durability studies that probe moisture effects typically evaluate performance losses at the module level, attributing global power losses to the overall humidity condition of the test environment while leaving local module behavior unknown. We leverage our recently published water reflectometry detection method and biased photoluminescence imaging to spatially correlate moisture content and cell performance over 2500 h of damp heat testing. These tests, carried out on glass–glass and glass–backsheet mini-modules at multiple temperatures and humidities, reveal two dominant modes of local cell performance loss—acute finger interruptions and cell-wide “background” series resistance increase. Finger interruptions occur earliest in glass–glass modules and at dry conditions. We do not observe any signs of contact corrosion at the front side in either module types. Still, glass–backsheet modules show a unique increase in series resistance at high humidities, suggesting a mechanism at the back contact. Overall, our results point to the humidity level of installation climate as a driving variable in selection of the bottom module layer.

We present a physics-based model to describe the kinetics of potential-induced degradation (PID) in p-Si photovoltaic (PV) modules, parametrized by the diffusivities of Na in the module stack, electric field in the SiNx, level of Na contamination, and segregation kinetics of Na in SiNx. Based on a sensitivity analysis on the expected electric field and levels of Na contamination at the surface of SiNx, we identify a relationship between the diffusivity of Na in the stacking faults present in the emitter and the kinetics of shunt resistance, $R_{\mathrm{sh}}$. These findings indicate a faster diffusion mechanism through the stacking faults than that which would be expected for bulk Si, for PID-prone p-Si modules. Our simulations imply that a decrease in the SiNx resistivity alone cannot explain robustness to PID-s, suggesting that a diffusivity dependence on the nitride chemistry may be responsible in part for PID-robust devices. We show that additional interface engineering could potentially reduce the ingress of Na and hence PID by allowing Na to segregate on interface layers.

Perovskite solar cells (PSCs) with an inverted structure (often referred to as the p–i–n architecture) are attractive for future commercialization owing to their easily scalable fabrication, reliable operation and compatibility with a wide range of perovskite-based tandem device architectures1,2. However, the power conversion efficiency (PCE) of p–i–n PSCs falls behind that of n–i–p (or normal) structure counterparts3–6. This large performance gap could undermine efforts to adopt p–i–n architectures, despite their other advantages. Given the remarkable advances in perovskite bulk materials optimization over the past decade, interface engineering has become the most important strategy to push PSC performance to its limit7,8. Here we report a reactive surface engineering approach based on a simple post-growth treatment of 3-(aminomethyl)pyridine (3-APy) on top of a perovskite thin film. First, the 3-APy molecule selectively reacts with surface formamidinium ions, reducing perovskite surface roughness and surface potential fluctuations associated with surface steps and terraces. Second, the reaction product on the perovskite surface decreases the formation energy of charged iodine vacancies, leading to effective n-type doping with a reduced work function in the surface region. With this reactive surface engineering, the resulting p–i–n PSCs obtained a PCE of over 25 per cent, along with retaining 87 per cent of the initial PCE after over 2,400 hours of 1-sun operation at about 55 degrees Celsius in air.

The mechanical properties of π-conjugated (semiconducting) polymers are a key determinant of the stability and manufacturability of devices envisioned for applications in energy and healthcare. These properties─including modulus, extensibility, toughness, and strength─are influenced by the morphology of the solid film, which depends on the method of processing. To date, the majority of work done on the mechanical properties of semiconducting polymers has been performed on films deposited by spin coating, a process not amenable to the manufacturing of large-area films. Here, we compare the mechanical properties of thin films of regioregular poly(3-heptylthiophene) (P3HpT) produced by three scalable deposition processes─interfacial spreading, solution shearing, and spray coating─and spin coating (as a reference). Our results lead to four principal conclusions. (1) Spray-coated films have poor mechanical robustness due to defects and inhomogeneous thickness. (2) Sheared films show the highest modulus, strength, and toughness, likely resulting from a decrease in free volume. (3) Interfacially spread films show a lower modulus but greater fracture strain than spin-coated films. (4) The trends observed in the tensile behavior of films cast using different deposition processes held true for both P3HpT and poly(3-butylthiophene) (P3BT), an analogue with a higher glass transition temperature. Grazing incidence X-ray diffraction and ultraviolet–visible spectroscopy reveal many notable differences in the solid structures of P3HpT films generated by all four processes. While these morphological differences provide possible explanations for differences in the electronic properties (hole mobility), we find that the mechanical properties of the film are dominated by the free volume and surface topography. In field-effect transistors, spread films had mobilities more than 1 magnitude greater than any other films, likely due to a relatively high proportion of edge-on texturing and long coherence length in the crystalline domains. Overall, spread films offer the best combination of deformability and charge-transport properties.

Increasing the stability of lead halide perovskites (LHPs) is critical for their practical application in solar cells and other technologies. Halide ion migration is one of the main contributors to instability and hysteresis in LHP solar cells. Here, we employ a series of Gedankenexperimentsto quantitatively establish the correlated effects of the A site cation motion, H bonding strength, and octahedral rotation on halide ion migration in APbBr3(A = Cs or methylammonium/MA) LHPs. We find that in cubic CsPbBr3, the increase of PbBr6octahedra rotation/tilting during ion migration lowers the halide ion migration barrier by at least 100 meV compared to the orthorhombic phase. In MAPbBr3, we show that halide ion migration is also assisted by MA cation rotation to re-establish H bonding, resulting in lower halide migration barriers. These results suggest that “locking” the organic cation via chemical and processing means can help mitigate halide migration-induced instability and reduced hysteresis in LHP solar cells.

We investigate semiconductor p–n junction formation by liquid-phase epitaxy (LPE) using metallic pastes incorporating traditional and nontraditional dopants. The LPE technique enables us to control the shape of doping profiles with a low thermal budget through the choice of solvent, total amount of solvent deposited, and process temperature. We focus here on the Al–B, Zn–P, and Sn–Ga chemistries to dope silicon regions using the chemicophysical properties of a low-eutectic-temperature metallic solvent acting as a matrix for the dissolution of a high concentration of a dopant. Additionally, we developed a capping method enabling doping across a large surface area wafer with a tunable thickness well below 1 μm without film dewetting. In good agreement with thermodynamic simulation of the LPE process, we demonstrate B- and Al-doped regions with a sheet resistance ranging from less than 10 to 300 Ω/sq between 650 and 800 °C, which is significantly lower than the typical temperatures of gas-phase doping processes. Comprehensive electrical simulations suggest that LPE p–n junctions with a low carrier recombination activity can be fabricated via the reduction of surface doping concentration and improved surface recombination velocity. Our investigation of exotic LPE chemistries suggests that emitter saturation currents below 50 fA/cm2could be achieved at doping concentrations relevant to solar cells.

Degradation due to electron beam exposure has posed a challenge in the use of electron microscopy to probe halide perovskite materials and devices. In this study, the interaction between the electron beam and the perovskite across acceleration voltages and at low probe currents is investigated in a scanning electron microscope (SEM) by monitoring the electron-beam-induced current (EBIC) response in perovskite solar cells in a plan-view configuration. SEM probe conditions are identified where dozens of repeated scans over a single region of the perovskite solar cell induce minimal electronic degradation. Overall, the induced current response of the perovskite device is found to strongly depend upon the beam condition: rapid decay occurs at high beam powers, the current activates at the lowest beam powers, and a newfound quasi-steady response is revealed at intermediate beam conditions. A quantitative window for the successful conduction of e-beam studies with minimal electronic degradation is revealed by evaluating induced current response over a wide range of perovskite devices, which invites broader use of SEM-based characterization techniques, including EBIC, as powerful techniques for correlative microscopy investigations.

Synchrotron micro- and nanoprobe beamlines have demonstrated great potential to advance photovoltaic devices. Most importantly, their small X-ray spot size has enabled the direct correlation of electrical performance with elemental composition at subgrain resolution for a variety of polycrystalline solar cells. Whereas the bulk of most inorganic semiconductors is stable under the high X-ray flux of focused X-ray beams, semiconductors with organic components are prone to a variety of degradation mechanisms. This is particularly critical to evaluate for the emerging organometal halide perovskite solar cells. Here, we investigate the effects of hard X-rays on the nanoscale performance and elemental distribution of these solar cells. We show that their composition does not change during common operando and in situ measurements at synchrotron nanoprobes. However, we found a significant X-ray-induced electronic degradation of solar cells with methylammonium lead iodide absorbers. Time- and dose-dependent measurements unveiled two characteristic degradation time constants on the order of 12 and 200 s that are independent of the X-ray flux. On the basis of heat and dose simulations, we attribute the fast decay to the dose-driven creation of recombination centers, while the slow decay is compatible with the observation of compositional changes. Finally, we detail how degradation-induced measurement artifacts can be outrun and showcase the high correlation of the X-ray-beam-induced current with the iodine and lead distribution.

The most important obstacle to widespread use of perovskite solar cells is their poor stability under operational stressors. Here, we systematically monitor the evolution of the photovoltaic performance of perovskite solar cells based on formamidinium-cesium lead iodide (FA0.9Cs0.1PbI3) for 600 h, under a series of controlled operational stressors. Although these devices exhibit reasonable thermal stability, their stability under illumination or stabilized power output (SPO) is far from commercial demands. Synchrotron-based nanoprobe X-ray fluorescence and X-ray-beam-induced current measurements reveal that current-blocking Cs-rich phases segregate during stress tests. The decrease in performance is in line with the increasing density of the Cs-rich clusters in area upon illumination. Theoretical calculations indicate that light-generated carriers provide the thermodynamic driving force for that phase segregation. Our findings correlate device performance to microscopic behavior and atomistic mechanisms and shed light on inhibiting the cation-dependent phase segregation during device operation.

Organic–inorganic hybrid perovskites have electronic and optoelectronic properties that make them appealing in many device applications1–4. Although many approaches focus on polycrystalline materials5–7, single-crystal hybrid perovskites show improved carrier transport and enhanced stability over their polycrystalline counterparts, due to their orientation-dependent transport behaviour8–10and lower defect concentrations11,12. However, the fabrication of single-crystal hybrid perovskites, and controlling their morphology and composition, are challenging12. Here we report a solution-based lithography-assisted epitaxial-growth-and-transfer method for fabricating single-crystal hybrid perovskites on arbitrary substrates, with precise control of their thickness (from about 600 nanometres to about 100 micrometres), area (continuous thin films up to about 5.5 centimetres by 5.5 centimetres), and composition gradient in the thickness direction (for example, from methylammonium lead iodide, MAPbI3, to MAPb0.5Sn0.5I3). The transferred single-crystal hybrid perovskites are of comparable quality to those directly grown on epitaxial substrates, and are mechanically flexible depending on the thickness. Lead–tin gradient alloying allows the formation of a graded electronic bandgap, which increases the carrier mobility and impedes carrier recombination. Devices based on these single-crystal hybrid perovskites show not only high stability against various degradation factors but also good performance (for example, solar cells based on lead–tin-gradient structures with an average efficiency of 18.77 per cent).

A short-wave infrared (SWIR) reflectometry method is developed to quantify the water content in solar modules in a noncontact approach. Water content has been implicated as a key factor in many module degradation pathways, including contact corrosion and yellowing. Despite these established issues, to date no robust method for quantitative in situ determination of water content in standard modules is available. The water reflectometry detection (WaRD) method provides this capability by leveraging the SWIR optical spectrum, in which water exhibits vibrational absorption bands, module components are highly transparent, and solar cell back reflectors are reflective. Here, we describe the operating principle and demonstrate measurement of moisture in encapsulated aluminum back surface field and passivated-emitter rear contact architectures over the full range of temperatures and relative humidity relevant to field operation and damp heat testing.

Using scanning X-ray diffraction microscopy, we investigate the relationship between residual strains from crystal growth in CsPbBr3thin-film crystals, their stability, and local photoluminescence (PL). We find that out-of-plane compressive strain that arises from cooldown from crystallization is detrimental to material stability under X-ray irradiation. We also find that the optical PL red-shifts as a result of the out-of-plane compressive strain. The sensitivity of the PL peak position to strain suggests possible applications such as stress-sensitive sensors. Mosaicity, the formation of small misorientations in neighboring crystalline domains we observe in some CsPbBr3single crystals, indicates the significant variations in the crystal quality that can occur even in single-crystal halide perovskites. The nanodiffraction results suggest that reducing local strains is a necessary path to enhance the stability of perovskite optoelectronic materials and devices from light-emitting diodes to high-energy detectors.

A significant improvement in the power conversion efficiency (PCE) and the environmental stability of n-Graphene/p-Si solar cells is indicated through effective n-doping of graphene, using low work function oxide capping layers. AlOx, deposited through atomic layer deposition, is particularly effective for such doping and in addition serves as an antireflection coating and a cell encapsulating layer. It is shown that the related charge transfer doping and interfacial engineering was crucial to achieve a record PCE of 12.5%. The work indicates a path forward, through work function engineering, for further efficiency gains in Gr-based solar cells.

To facilitate cost-effective manufacturing of boron-implanted silicon solar cells as an alternative to BBr3 diffusion, we performed a quantitative test of the gettering induced by solar-typical boron-implants with the potential for low saturation current density emitters (<;50 fA/cm2). We show that depending on the contamination level and the gettering anneal chosen, such boron-implanted emitters can induce more than a 99.9% reduction in bulk iron point defect concentration. The iron point defect results as well as synchrotron-based nano-X-ray-fluorescence investigations of iron precipitates formed in the implanted layer imply that, with the chosen experimental parameters, iron precipitation is the dominant gettering mechanism, with segregation-based gettering playing a smaller role. We reproduce the measured iron point defect and precipitate distributions via kinetics modeling. First, we simulate the structural defect distribution created by the implantation process, and then we model these structural defects as heterogeneous precipitation sites for iron. Unlike previous theoretical work on gettering via boron- or phosphorus-implantation, our model is free of adjustable simulation parameters. The close agreement between the model and experimental results indicates that the model successfully captures the necessary physics to describe the iron gettering mechanisms operating in boron-implanted silicon. This modeling capability allows high-performance, cost-effective implanted silicon solar cells to be designed.

There is no doubt about the potential offered by the low-cost fabrication and high efficiency of  hybrid organic–inorganic perovskite solar cells. However, the service lifetimes of these devices must be increased from months to years to capitalize on their potential. The archetypal hybrid perovskite for solar cells, methylammonium lead iodide (CH3NH3PbI3, abbreviated MAPI), readily degrades in ambient atmosphere under standard operating conditions. Understanding the origin and effects of this degradation can pave the way to better engineer photovoltaic devices and the perovskite material itself. Herein we present the effects of varying pressure on the electrical performance of MAPI solar cells. Solar cell parameters, especially open circuit voltage, are significantly affected by the total ambient pressure and present an unexpected reversible behavior upon pressure cycling. We complement photoluminescence studies as a function of ambient atmosphere and temperature with first-principles density functional theory (DFT) calculations. The results suggest that the reversible intercalation of water in MAPI is a necessary component underlying this behavior.

Unveiling the correlation between elemental composition, Fermi-level splitting, and charge collection in perovskite solar cells (PSCs) when exposed to different environments is crucial to understanding the origin of defects. This will enable defect engineering to achieve high-performance and long-lasting PSCs. In this paper, we measured, for the first time, the spatial distribution and charge-collection efficiency at the nanoscale by synchrotron-based X-ray fluorescence (XRF) and X-ray beam-induced current (XBIC) with subgrain resolution, and we observe a correlation between Pb/I ratio and charge-collection efficiency. In contrast with other thin-film solar cells, PSCs are highly sensitive to ambient conditions (atmosphere and illumination). As the XRF and XBIC measurements were conducted in vacuum under an X-ray source illumination, the impact of measurement conditions on the cells needs to be taken into account. Furthermore, necessary conditions for quantification of XRF/XBIC measurements, such as film homogeneity, are not fulfilled in the case of PSCs. Therefore, we will discuss fundamentals of XRF/XBIC measurements of PSCs that will enable reliable, quantitative, high-resolution measurements of elemental distribution and charge collection.

Ion implantation is a promising method to implement a high-performance emitter for crystalline silicon solar cells. However, an implanted emitter redistributes and mitigates harmful metal impurities to a different degree than a diffused one. This paper quantitatively assesses the effect of iron contamination level on the bulk diffusion length and open-circuit voltage of phosphorus-implanted solar cells manufactured with varying gettering parameters. By synchrotron-based micro-X-ray fluorescence measurements, we directly observe a process-dependent iron precipitate size distribution in the implanted emitters. We show that controlling the iron precipitate size distribution is important when optimizing final cell performance and discover a tradeoff between large shunting precipitates in the emitter and a high density of recombination active small precipitates in the wafer bulk. We present a heterogeneous iron precipitation model capable of reproducing the experimentally measured size distributions. We use the model to show that the dominant gettering mechanism in our samples is precipitation and that implanted emitters with surface phosphorus concentrations around 2×1019 cm-3 induce little-to-no segregation-based gettering. Based on this finding, we discuss optimal gettering strategies for industrial silicon solar cells with implanted emitters.

Phosphorus diffusion gettering of multicrystalline silicon solar cell materials generally fails to produce material with minority-carrier lifetimes that approach that of gettered monocrystalline wafers, due largely to higher levels of contamination with metal impurities and a higher density of structural defects. Higher gettering temperatures should speed the dissolution of precipitated metals by increasing their diffusivity and solubility in the bulk, potentially allowing for improved gettering. In this paper, we investigate the impact of gettering at higher temperatures on low-purity multicrystalline samples. To analyze the gettering response, we measure the spatially resolved lifetime and interstitial iron concentration by microwave photoconductance decay and photoluminescence imaging, and the structural defect density by Sopori etching and large-area automated quantification. Higher temperature phosphorus diffusion gettering is seen to improve metal-limited multicrystalline materials dramatically, especially in areas of low etch pit density. In areas of high as-grown dislocation density in the multicrystalline materials, it appears that higher temperature phosphorus diffusion gettering reduces the etch pit density, but leaves higher local concentrations of interstitial iron, which degrade lifetime.

The extraction of metal impurities during phosphorus diffusion gettering (PDG) is one of the crucial process steps when fabricating high‐efficiency solar cells using low‐cost, lower‐purity silicon wafers. In this work, we show that for a given metal concentration, the size and density of metal silicide precipitates strongly influences the gettering efficacy. Different precipitate size distributions can be already found in silicon wafers grown by different techniques. In our experiment, however, the as‐grown distribution of precipitated metals in multicrystalline Si sister wafers is engineered through different annealing treatments in order to control for the concentration and distribution of other defects. A high density of small precipitates is formed during a homogenization step, and a lower density of larger precipitates is formed during extended annealing at 740 °C. After PDG, homogenized samples show a decreased interstitial iron concentration compared to as‐grown and ripened samples, in agreement with simulations.

The evolution of Fe-related defects is simulated for di erent P di usion gettering (PDG) processes which are applied during silicon solar cell processing. It is shown that the introduction of an extended PDG is bene cial for some as-grown Si materials but not essential for all of them. For mc-Si wafers with an as-grown Fe concentration 14 cm3, a good reduction of the Fei concentration and increase of the electron lifetime is achieved during standard PDG. For mc-Si wafers with a higher as-grown Fe concentration the introduction of defect engineering tools into the solar cell process seems to be advantageous. From comparison of standard PDG with extended PDG it is concluded that the latter leads to a stronger reduction of highly recombination active Fei atoms due to an enhanced segregation gettering e ect. For an as-grown Fe concentration between 1014 cm3 and 1015 cm3, this enhanced Fei reduction results in an appreciable increase in the electron lifetime. However, for an as-grown Fe concentration >1015 cm3, the PDG process needs to be optimized in order to reduce the total Fe concentration within the wafer as the electron lifetime after extended PDG keeps being limited by recombination at precipitated Fe.

Ferroelectric nanomaterials offer the promise of switchable electronic properties at the surface, with implications for photo- and electrocatalysis. Studies to date on the effect of ferroelectric surfaces in electrocatalysis have been primarily limited to nanoparticle systems where complex interfaces arise. Here, we use MBE-grown epitaxial BaTiO3thin films with atomically sharp interfaces as model surfaces to demonstrate the effect of ferroelectric polarization on the electronic structure, intermediate binding energy, and electrochemical activity toward the hydrogen evolution reaction (HER). Surface spectroscopy and ab initioDFT+U calculations of the well-defined (001) surfaces indicate that an upward polarized surface reduces the work function relative to downward polarization and leads to a smaller HER barrier, in agreement with the higher activity observed experimentally. Employing ferroelectric polarization to create multiple adsorbate interactions over a single electrocatalytic surface, as demonstrated in this work, may offer new opportunities for nanoscale catalysis design beyond traditional descriptors.

A trap‐corrected bias–temperature–stress (TraC‐BTS) method to quantify the kinetics of ion migration in dielectrics based on capacitance–voltage measurements is presented. The method is based on the extraction of flatband potential (Vfb) shifts in metal–insulator–semiconductor test structures an enables the reliability assessment of semiconductor dielectrics and solar cells. Herein, it is shown that carrier trapping in the dielectric must be accounted for, as it strongly affects the measurement of flatband potential in silicon‐nitride‐based capacitors. This effect is corrected by isolating the contribution of trapping on Vfbusing contamination‐free control devices. A specific drift‐diffusion model of the ion kinetics presented herein allows the extraction of ion diffusivity. An Arrhenius relationship is obtained for sodium diffusivity in silicon nitride in a temperature range from 30 °C to 90 °C at an electric field of 1 MV cm−1, yielding a prefactor D0=1×10−14cm2s−1and an activation energy Ea=0.14eV, with a 95% confidence interval of [0.07,0.21] eV for the diffusivity. These quantitative kinetics confirm that silicon nitride may be a poor sodium migration barrier under a significant electric field. An automated method is developed to quantify ion migration in dielectrics. Ions migrate through the dielectric layer of metal–dielectric–semiconductor capacitors under an externally applied bias at several temperatures. Flatband voltage shift is measured as a function of time, and a physical model is proposed to extract the activation energy and diffusion prefactor.