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• Photovoltaic recycling is becoming an essential part of overall waste management. • High-value photovoltaic waste recycling recovers economically valuable materials. • Life cycle assessment hotspots are transportation, energy consumption and chemicals. • Photovoltaic recycling policies and legislation require further development. Silicon-based photovoltaics (Si-PVs) are a leading renewable energy technology that has seen global acceptance. Si-based PV has resulted in notable market growth, particularly over the past several decades. Increased PV utilization and continued production increases have translated to burgeoning PV waste generation as they reach PV end-of-life. As a result, the focus on processes to treat waste PVs in anticipation of the large quantities of waste, are coming into focus. Some of the PV waste treatment methods do manage to treat the waste but fail to recover the economic value of the PV constituent materials, resulting in downcycling. On the other hand, high value recycling has been of interest because they offer options to recover as much of the materials of limited availability, promote a circular economy, offer economic value, and help strength supply chain. However, recovering these materials from PV waste involves complex operations relative to the downcycling. This review focuses on high value recycling, highlighting the different operations that are performed during each stage and the products obtained through the recycling operations. Further, life cycle assessments related to PV waste treatment are presented in this work to outline the environmental implications associated with PV waste recycling. Finally, the status of global PV waste management policies is presented with a focus on major markets and the involvement of various organizations. [ABSTRACT FROM AUTHOR]

Over the past five years, there has been a significant increase in both the intensity of research and the performance of crystalline silicon devices which utilize metal compounds to form carrier-selective heterocontacts. Such heterocontacts are less fundamentally limited and have the potential for lower costs compared to the current industry dominating heavily doped, directly metalized contacts. A low temperature (≤230 °C), TiO x /LiF x /Al electron heterocontact is presented here, which achieves mΩcm 2 scale contact resistivities ρ c on lowly doped n-type substrates. As an extreme demonstration of the potential of this heterocontact, it is trialed in a newly developed, high efficiency n-type solar cell architecture as a partial rear contact (PRC). Despite only contacting ≈1% of the rear surface area, an efficiency of greater than 23% is achieved, setting a new benchmark for n-type solar cells featuring undoped PRCs and confirming the unusually low ρ c of the TiO x /LiF x /Al contact. Finally, in contrast to previous versions of the n-type undoped PRC cell, the performance of this cell is maintained after annealing at 350–400 °C, suggesting its compatibility with conventional surface passivation activation and sintering steps.

Nanometer scale interfacial layers between the metal cathode and the n-type semiconductor play a critical role in enhancing the transport of charge carriers in and out of optoelectronic devices. Here, a range of nanoscale alkali and alkaline earth metal carbonates (i.e., potassium, rubidium, caesium, calcium, strontium, and barium) are shown to function effectively as electron heterocontacts to lightly doped n-type crystalline silicon (c-Si), which is particularly challenging to contact with common metals. These carbonate interlayers are shown to enhance the performance of n-type c-Si proof-of-concept solar cells up to a power conversion efficiency of ≈19%. Furthermore, these devices are thermally stable up to 350 °C and both the caesium and barium carbonates pass a standard 1000 h damp heat test, with >95% of their initial performance maintained. The temperature and humidity stable electron heterocontacts based on alkali and alkaline earth metal carbonates show a high potential for industrial feasibility and longevity for deployment in the field.

Carrier-selective passivating contacts for effective electron and hole extraction are crucial to the attainment of high efficiency in crystalline silicon (Si) solar cells. In this comprehensive review, the principle of carrier extraction and recombination mechanisms in conventional industrial Si solar cells are discussed first. Passivating contacts based on (i) amorphous hydrogenated Si and (ii) polysilicon/silicon oxide are next reviewed, with emphasis on carrier selectivity mechanisms including contact layer band alignment with silicon, and localized carrier transport in ultrathin oxides. More recent developments in dopant-free passivating contacts deposited by lower-cost fabrication processes with lower thermal budget are then described. This third category of non-Si based electron- and hole-selective passivating contacts include transition metal oxides, alkali/alkali earth metal fluorides and organic conjugated polymers. The photovoltaic performance of asymmetric double heterojunction Si solar cells fabricated using these non-Si passivating contacts and their stability in damp heat conditions are discussed and compared with Si based passivating contacts. [ABSTRACT FROM AUTHOR]

Thin, flexible, and efficient silicon solar cells would revolutionize the photovoltaic market and open up new opportunities for PV integration. However, as an indirect semiconductor, silicon exhibits weak absorption for infrared photons and the efficient absorption of the full above bandgap solar spectrum requires careful photon management. This review paper provides an overview on the fundamental physics of light trapping and explains known theoretical limits. Technologies that have been developed to improve light trapping will be discussed, and limitations will be addressed. [ABSTRACT FROM AUTHOR]

Carrier-selective passivating contacts for effective electron and hole extraction are crucial to the attainment of high efficiency in crystalline silicon (Si) solar cells. In this comprehensive review, the principle of carrier extraction and recombination mechanisms in conventional industrial Si solar cells are discussed first. Passivating contacts based on (i) amorphous hydrogenated Si and (ii) polysilicon/silicon oxide are next reviewed, with emphasis on carrier selectivity mechanisms including contact layer band alignment with silicon, and localized carrier transport in ultrathin oxides. More recent developments in dopant-free passivating contacts deposited by lower-cost fabrication processes with lower thermal budget are then described. This third category of non-Si based electron- and hole-selective passivating contacts include transition metal oxides, alkali/alkali earth metal fluorides and organic conjugated polymers. The photovoltaic performance of asymmetric double heterojunction Si solar cells fabricated using these non-Si passivating contacts and their stability in damp heat conditions are discussed and compared with Si based passivating contacts.

Photovoltaic (PV)‐based solar hydrogen generation is a promising pathway for the scalable production of renewable fuels. Understanding the limitations of solar‐to‐hydrogen (STH) conversion efficiencies is critical to identify performance limits and conceptualize practical device designs. Herein, the losses in PV‐based solar hydrogen generation systems are quantified and the potential of loss‐mitigation techniques to improve the STH efficiency is assessed. The analysis shows that the two largest losses in an ideal system are current and voltage mismatches due to suboptimal system configurations and energy lost as heat in the PV component. A temperature‐dependent model is developed to evaluate the relative potential of two techniques to mitigate these losses: decoupling the PV system to remove current and voltage matching requirements and thermal integration to use the heat losses from PV to increase the electrolyte temperature and improve the reaction dynamics for water splitting. It is shown that optimal system configuration strategies provide more than three times the STH efficiency increase of thermal integration at high operating temperatures. Combining both techniques results in predicted STH efficiencies approaching 20% for low‐cost perovskite–silicon tandem‐based systems with earth‐abundant catalysts at realistic working temperatures.

Minimising charge losses at silicon interfaces is a major development area for highly efficient solar cells. Here we report on the interface improvements achieved by establishing a surface electric field during low-temperature firing of dielectric thin films. By inducing a corona electric field on the surface of a thin film stack, we observe significant modifications to the silicon-dielectric interface upon annealing, which correlate with the characteristics of interface defects. The passivation properties of the interfaces strongly depend on the polarity and strength of the electric field during firing, as well as the dielectric materials in the layer stack. We show that the surface electric fields not only influence surface carrier population but also affect the resulting chemical interface properties post-annealing. It is postulated that hydrogen migration plays a role in these observed effects. Leveraging the corona-induced electric field enables fine-tuning of both the chemical and field-effect passivation in thin film surface dielectrics, resulting in recombination current densities as low as 2.8 fA cm−2 in research-grade float zone silicon, and 14 fA cm−2 in industrial-grade textured silicon. The simplicity and versatility of the thin film electric polarisation enable a new strategy for controlling and exploiting the chemical enhancement of interfaces in solar cell devices, from current TOPCon and PERC devices to future multijunction silicon-based cells. • Hydrogen passivation from dielectrics is central to improving silicon solar cell performance. • Charge-assisted field effect passivation not only controls carrier population, but also affects interface chemistry. • Chemical passivation of Si-SiO 2 -SiN x interfaces depends on the polarity and strength of the surface electric field. • Optimal processing requires control of surface electric fields, chemical interface, hydrogenation and charge migration. • Understanding the interplay of hydrogen and electric fields is crucial for optimising silicon solar cell performance. [ABSTRACT FROM AUTHOR]

In the framework of the PVadapt H2020 project, a sustainable and fully adaptable building-integrated photovoltaic–thermal (BIPVT) system of substantially lower cost than conventional in-market solutions will be developed. A flexible automated process will be employed to produce PV modules as well as elements with integrated heat pipe-based heat recovery. These active energy components will be combined with passive components with structural, thermal, and other functions to produce prefabricated modules. A smart envelope System, featuring grid connectivity, load prediction/shifting, and insolation/temperature predictive algorithms, will be integrated in the BIPVT to maximize energy efficiency and cost saving. The unit cost of production, the levelized cost of energy (LCOE), and the payback period of the multifunctional BIPVT module will be below 200 €/m2, 2 ct/kWh, and 10 years, respectively.

Photovoltaic (PV) conversion of solar energy starts to give an appreciable contribution to power generation in many countries, with more than 90% of the global PV market relying on solar cells based on crystalline silicon (c-Si). The current efficiency record of c-Si solar cells is 26.7%, against an intrinsic limit of ~29%. Current research and production trends aim at increasing the efficiency, and reducing the cost, of industrial modules. In this paper, we review the main concepts and theoretical approaches that allow calculating the efficiency limits of c-Si solar cells as a function of silicon thickness. For a given material quality, the optimal thickness is determined by a trade-off between the competing needs of high optical absorption (requiring a thicker absorbing layer) and of efficient carrier collection (best achieved by a thin silicon layer). The efficiency limits can be calculated by solving the transport equations in the assumption of optimal (Lambertian) light trapping, which can be achieved by inserting proper photonic structures in the solar cell architecture. The effects of extrinsic (bulk and surface) recombinations on the conversion efficiency are discussed. We also show how the main conclusions and trends can be described using relatively simple analytic models. Prospects for overcoming the 29% limit by means of silicon/perovskite tandems are briefly discussed.

Abstract Laser Centre UPM is one of the leading Research Centers in Spain in the field of industrial applications of high power lasers. Founded in 1998 in the oldest and largest Spanish Technical University, Universidad Politécnica de Madrid, its activity is focused in technological transfer of laser-based processes to industry. With an important experience in laser micromachining using fast and ultrafast lasers, one of the fields in which its activity has produced more relevant results is laser process development for photovoltaic (PV) industry. Starting in 2004, its activity in this field in collaboration with other public Spanish institutions and other industrial partners has had a remarkable scientific and technological impact. Unfortunately, this activity was seriously restricted since 2010 due to the economic crisis in general and the photovoltaic industry evolution in particular. However, the background acquired in some particular applications and the inertia obtained with that activity has opened new fields of activity of Laser Center UPM in advanced laser-based processes for biomedicine. This paper summarizes the main achievements of Laser Center UPM in PV and how it performed the transition to new applications in a completely different sector, like biomedicine, using the experienced accumulated in the development of new laser based processes for PV. [ABSTRACT FROM AUTHOR]

A tunneling atomic layer deposited (ALD) AlO x layer was inserted in a Si|SiO x |AlO x |MoO x |metal tunnel diode structure to investigate the impact of fixed interface charge on Schottky barrier height. ALD AlO x provides a synthesis-tunable fixed charge and can provide excellent field effect passivation at the SiO x |AlO x interface. A large (>1 × 1012 q.cm−2) negative fixed charge density was expected to decrease Schottky barrier height on p-type silicon and increase Schottky barrier height on n-type silicon by up to 0.4 eV based on an electrostatic model. Fixed charge density and interface trap state density were measured using a thick layer of AlO x in metal oxide semiconductor capacitor structures (MOSCAPs); Schottky barrier height and specific contact resistivity were measured using a tunneling-active layer of AlO x in contacted structures with MoO x. In some samples, HfO x interface layers were inserted between AlO x and silicon to quench the fixed negative charge. The Schottky barrier height was found to vary with processing conditions but did not have a strong correlation with expected fixed charge density. Thus, while fixed charge may play a role in determining the Schottky barrier height, other parameters also have significant affect. Further work is needed to minimize contact resistivity and elucidate other factors impacting the Schottky barrier height. • Effect of SiO x.|ALD AlO x fixed charge on ALD MoOx-based selective contact studied with varied processing. • Schottky barrier height found not to vary solely with Nf; other factors contribute to changes. • Schottky barrier height and fixed charge density affected by silicon surface preparation, AlO x deposition temperature, annealing, and the insertion of ALD HfO x at the SiO x.|AlO x interface. • Achieved Schottky barrier height range between <0.2 eV and 1.0 eV with p-type and n-type Si.|SiO x |AlO x |MoO x |Al structures. • Contact resistivity shown indicated to be highly dependent on SiO x layer and/or total oxide thickness. [ABSTRACT FROM AUTHOR]

The alneal is one of the most effective methods of electrically passivating a silicon surface, and has been used by numerous research groups since the 1980s. In this work, we present an enhanced alneal process that substantially improves its effectiveness. Previously, the success afforded by the standard alneal has been attributed to the chemical passivation provided by hydrogenation of the Si-SiO 2 interface. However, the work presented here shows that it is possible to enhance the surface passivation by simultaneously introducing a component of Field Effect Passivation (FEP). Where the standard alneal is seen to provide lifetimes of ~2.1 ms, equivalent to a surface recombination velocity (SRV) of 3.3 cm/s, the enhanced alneal can provide a lifetime of 5.6 ms on 1 Ω cm, n-type Si, equivalent to a SRV 0.4 cm/s. The charge required for this enhanced passivation can be introduced in the order of minutes and has the potential to be introduced at the same time as the aluminium is deposited, thus, resulting in no extra processing time. Secondary ion mass spectroscopy showed that the nature of the charge is likely to be K and Na cations residing at the Si-SiO 2 interface. The possibility of increasing the surface passivation beyond that of the standard alneal points to the importance of both chemical and field effect components of passivation, and is therefore of significant interest to high efficiency silicon solar cell research. [ABSTRACT FROM AUTHOR]

Sub-stoichiometric molybdenum oxide (MoO x ) films are commonly deposited on crystalline silicon (c-Si) solar cells by thermal evaporation, a process that requires high vacuum and provides limited control of oxide stoichiometry and in consequence limited control of hole transport properties. Here, we report on a method of forming MoO x films on crystalline silicon wafer surfaces by spin-coating hydrogen molybdenum bronze solutions. It is shown that a ∼2.8 nm thick interfacial SiO x layer forms under the spin-coated MoO x films and that the as-deposited MoO x is amorphous and sub-stoichiometric ( x = 2.73), with the concentration of oxygen vacancies in the MoO x being able to be reduced by annealing in air. The as-deposited MoO x films show comparable contact resistivity and passivation quality on c-Si wafers to thermally-evaporated MoO x , demonstrating their potential to be an effective hole-selective contact layer for c-Si solar cells and an alternative for thermally-evaporated films. [ABSTRACT FROM AUTHOR]

Two testing methods for photovoltaic (PV) plants, an infrared (IR)-measurement aerial system and a monitoring system on module level, are compared with respect to their capabilities for identifying irregularities of PV panels in a PV plant. For the first method, a hypothesis is tested that infrared temperature and module power can be correlated with an empirical linear correlation using the raw measurement data of the second method. A workaround is proposed how to quantify power losses for unknown PV plants showing at the same time how power losses depend on ambient conditions. Also, the data is used to improve results from the IR-measurements. The second method is explained to compare the two methods. It is shown that each method offers different advantages, helping to properly assess and schedule O&M measures. [ABSTRACT FROM AUTHOR]

The silicon photovoltaic industry is currently shifting towards lightly doped emitters. These have electrical properties that benefit solar cells, compared to the traditional heavily doped emitters. This move brings new challenges, as gettering efficiencies of impurities are lowered as the doping reduces. This is particularly problematic in multicrystalline silicon (mc-Si) since cell performance is typically boosted by the effective gettering of such impurities. In prior work, we proposed the novel gettering technique, saw damage gettering (SDG), which improved effective carrier lifetime of standard performance mc-Si red zone material. In this work, we expand the study of SDG to various types of industrially relevant mc-Si: upgraded metallurgical grade (UMG), high performance bottom red zone (HPRZ), and diamond sawn high performance (DHP). The optimal condition for SDG is found to be an annealing temperature of 850 °C. With this condition it was demonstrated that the effective carrier lifetime can be increased in all silicon types upon SDG. The largest increase was observed for HPRZ material by a factor of 10, and the largest final effective lifetime post SDG was that of UMG, with τeff = 61.3 µs. SDG is a potentially viable gettering method to work in conjunction with lightly doped emitters in removing the impurities of mc-silicon feedstock and thus, improving the efficiency of the cells made therefrom. [ABSTRACT FROM AUTHOR]

We report and explain the photoluminescence (PL) spectra from crystalline silicon (c-Si) wafers passivated by hydrogenated amorphous silicon (a-Si:H) films under various measurement conditions, utilizing the different absorption coefficients and radiative recombination mechanisms in c-Si and a-Si:H. By comparison with the luminescence properties of a-Si:H, we also demonstrate that SiN x films deposited under certain silicon-rich conditions yield luminescence spectra similar to those of a-Si:H, indicating the presence of an a-Si:H-like phase in the SiN x films. This causes a reduction in the blue response of the solar cells via parasitic absorption. In addition, with the ability to detect the specific emission from heavily-doped silicon via band-gap narrowing effects, we can unambiguously separate individual spectral PL signatures of three different layers in a single substrate: the SiN x passivation films, the diffused layers, and the underlying c-Si substrate. Finally, we apply this technique to evaluate parasitic absorption in the passivation films, and the doping density of the diffused layers on different finished solar cells, highlighting the value of this nondestructive contactless, micron-scale technique for photovoltaic applications. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic actuation-based optoelectronic active catheter tracking system for magnetic resonance imaging (MRI). The system incorporates a radio frequency (RF) microelectromechanical system (MEMS) resonator array actuated by the Lorentz force induced due to the strong dc magnetic field available in MRI environment. Power transfer to the system and the actuation detection are done optically via fiber optic cables that replace conventional conductive transmission lines; thereby, enabling the tracking system to function safely under MRI. The complementary metal–oxide–semiconductor (CMOS) receiver, optically powered by a supply unit housing an on-chip silicon photovoltaic cell, detects the location of the catheter tip. The RF MEMS resonator array transmits the position data by transducing the electrical signal into a resonant mechanical vibration linearly. The optical reading of this actuation can be done by diffraction grating interferometry or laser doppler vibrometry. The fabricated resonator array is tested with the optically powered CMOS chip (0.18-$\mu$ m UMC technology) in laboratory conditions. The driving electrical current supplied by the chip for resonator actuation is 25-$\mu$A rms, where the magnetic field provided by the experimental setup is 0.62 T. The resonator array is observed to be functional with real-world application by showing a frequency response of 10 dB, which will be enhanced further under the stronger magnetic field available in 3-T MRI. [ABSTRACT FROM PUBLISHER]

Upconversion is a promising technique for harvesting sub-band-gap photons in photovoltaic devices. In this work, the optimum erbium (Er 3+ ) doping within the efficient upconverting host material hexagonal sodium yttrium fluoride (β-NaYF 4 ) is investigated for a wide range of irradiance values and under broadband excitation (80±1 nm). Measurements of the internal photoluminescent quantum yield ( iPLQY ) have been conducted over two orders of magnitude in irradiance, the corresponding solar concentrations characterised, and the external photoluminescent quantum yield ( ePLQY ) determined. The iPLQY measurements required calibration due to overlap of absorption and re-emission in the range of 1450–1600 nm. The highest iPLQY was for 20% Er 3+ with a value of 10.7±1.2% and a normalised efficiency of (5.43±0.90)×10 −4 cm 2 W −1 at an irradiance of 1.97±0.24 MW m −2 ((108±13)×10 3 Suns). More importantly for application to silicon solar cells, the highest ePLQY was for 25% Er 3+ and was measured to be 6.6±0.7% ((3.35±0.56)×10 −4 cm 2 W −1 ), which agrees well with monochromatic investigations. The 25% Er 3+ sample was shown to be more efficient due to an anomalous increase and broadening of the absorption in comparison to lower concentrations. Furthermore, energy transfer mechanisms are proposed for the reduced efficiency of higher concentrations and depletion of the upconversion luminescence. [ABSTRACT FROM AUTHOR]

Abstract: A new method to obtain antireflective and passivation layers for p-type silicon solar cells is presented. Hydrogenated silicon carbon nitride (SiCxNy:H) films are obtained by low frequency plasma enhanced chemical vapor deposition (PECVD), using ammonia (NH3) and tetramethylsilane (TMS) as precursors; the influence of the deposition temperature and gas ratio on the film composition and properties is studied. It can be observed that the chemical composition of the film as well as its optical and passivation properties vary strongly with the gas ratio and temperature used. The optimal conditions with respect to the refractive index, the absorption coefficient and the minority carrier lifetime after rapid thermal annealing are determined. These conditions lead to an approximate stoichiometry of SiC0.6N0.8:H thin film including nearly 5×1021 cm−3 hydrogen bonds. [Copyright &y& Elsevier]

Abstract: The optical reflectivity of polished silicon covered by a forest of vertically standing gold nanowires (grown inside the pores of an anodic alumina matrix) is found to be considerably smaller than that of bare polished silicon and strongly influenced by scattering of light by the nanowires. We propose a phenomenological modification to the Maxwell–Garnett effective medium theory formula to account for this effect. We also find that the gold nanowire/alumina film has interesting optical properties, such as transparency in the mid-infrared and high absorbance in the visible, and may be used as a low reflectivity coating and a low-pass filter. [Copyright &y& Elsevier]

Abstract: The surface recombination velocity is a critical parameter in silicon device applications including solar cells. In this work, we developed and applied a contactless optical/radio-frequency technique to provide quick, contactless measurement of the surface recombination velocity. The basic technique is to probe the excess carrier lifetime in the surface and bulk regions of a semiconductor wafer by varying the excitation wavelength. Here, we have derived a theoretical functional model that describes the experimental photoconductive transient. A curve fitting procedure provides a determination for both the bulk recombination lifetime and the surface recombination velocity. [Copyright &y& Elsevier]

Abstract: Dark conductivity of silicon wafers has been measured as a function of doping levels, sample’s geometry, and under gamma irradiation conditions. It has been shown that measurements of samples conductivity under different operating conditions can be used as an efficient method for material quality evaluation. In addition, gamma irradiation gives future information on Si-wafer quality, where it can effectively influence the material properties. The induced change in conductivity is discussed following the mathematical difference of conductivity modulation mode. Using this model conductivity measurements could be considered as a good and simple technique for determining the silicon quality and for further development in silicon processing. [Copyright &y& Elsevier]

Recently, lead halide perovskite solar cells have become a promising next-generation photovoltaics candidate for large-scale application to realize low-cost renewable electricity generation. Although perovskite solar cells have tremendous advantages such as high photovoltaic performance, low cost and facile solution-based fabrication, the issues involving lead could be one of the main obstacles for its commercialization and large-scale applications. Lead has been widely used in photovoltaics industry, yielding its environmental and health issues of vital importance because of the widespread application of photovoltaics. When the solar cell panels especially perovskite solar cells are damaged, lead would possibly leak into the surrounding environment, causing air, soil and groundwater contamination. Therefore, lots of research efforts have been put into evaluating the lead toxicity and potential leakage issues, as well as studying the encapsulation of lead to deal with leakage issue during fire hazard and precipitation in photovoltaics. In this review, we summarize the latest progress on investigating the lead safety issue on photovoltaics, especially lead halide perovskite solar cells, and the corresponding solutions. We also outlook the future development towards solving the lead safety issues from different aspects. [Display omitted] • Lead in perovskite photovoltaics poses potential risks to human health and ecosystem. • Water-soluble and bioavailable lead that leaks from damaged PSCs is dangerous. • Fail-safe encapsulation and safe device configuration are developed for lead leakage. • End-of-life PSCs as hazardous wastes should be taken into account before commercialization. [ABSTRACT FROM AUTHOR]

A key efficiency-limiting factor in silicon-based photovoltaic (PV) devices is the quality of the silicon material itself. With evolving cell architectures that better address other efficiency-loss channels in the device, the final device efficiency becomes increasingly sensitive to the contaminants in the silicon wafer bulk. However, due to cost constraints, silicon materials for PV are inherently less pure and further contamination during device fabrication is commonly found, especially in mass production environments. Metallic impurities are ubiquitous and abundant, and they are strong efficiency-loss channels in the device if not removed. Gettering is the process of removing metallic impurities to a less harmful region of the device, and is therefore an essential aspect of the cell fabrication process. This article presents an up-to-date review of the gettering techniques and processes in silicon solar cells, providing a complete picture of the possible gettering sinks and routes in various cell architectures. The article starts by explaining the common nomenclatures in gettering and summarising recent updates to the solubility and diffusivity data of the common 3d transition metals in silicon. Then the three-step gettering process (release, diffusion, capture) is explained, and its implications for solar-grade cast-grown silicon (in terms of release) and various cell architectures (in terms of diffusion) are discussed. The main focus of the article is to summarise and review the various capture approaches in the context of silicon PV. These include phosphorus diffusion, boron diffusion, selective doping via ion implantation, state-of-the-art polycrystalline-silicon/oxide passivating contact structures, dielectric films (silicon nitride and aluminium oxide), aluminium alloying, surface damaged regions including black silicon, and internal gettering in cast-grown silicon by existing crystallographic defects. Their gettering effects, current understanding of the gettering mechanisms, modelling, improvement strategies, implementation in processing and potential impacts on cell performance are reviewed. [ABSTRACT FROM AUTHOR]