The study delved into the alteration of chemical and physical properties of various non-conventional encapsulant materials following UV aging. Three polymer classes were scrutinized: ethylene vinyl acetate (EVA), traditionally utilized as an encapsulant, alongside thermoplastic polyolefins (TPO) and polyolefin elastomers (POE), emerging as alternatives to EVA, promising to mitigate reliability issues in photovoltaic modules associated with EVA degradation. Multiple commercially available encapsulating polymer films from each class, featuring diverse chemical formulations, were examined. To simulate harsh environmental conditions, a climatic chamber was employed to assess the variation in properties of different polymer films pre- and post-UV aging. The study investigated the correlation between chemical structure, formulation, encapsulant degradation, and durability under simulated UV stress, evaluating alterations in thermal stability, optical transmittance, crystallinity, yellowing index, and chemical degradation; furthermore, the analysis addresses the properties of the polymers used in their possible degrees of recyclability

Among the various architectures proposed to produce both four-terminal and two-terminal Perovskite/silicon tandem solar cells, the two-terminal (2T) mechanically stacked tandem configuration combines the simplicity of an independent fabrication and optimization of perovskite and silicon sub cells with a reduced system complexity associated with the 2T architecture. To improve the performance of the 2T mechanically stacked tandem several material and fabrication aspects need to be addressed and combined in a synergetic way. A holistic approach able to improve the photovoltaic performance working on the energy gap tunability, the perovskite thickness and composition, the defect passivation and the device architecture is demonstrated. This technique allows to raise the achievable Power Conversion Efficiency reaching in the best case 31 % (30 % stabilized and 28.32 % on average) on active areas larger than 1 cm(2).

Today to achieve high efficiency solar cells, the crystalline silicon (c-Si) heterojunction (HJ) represents one of the best available options. The key factor of its success is the high open circuit voltage (Voc) achievable, because of the excellent surface passivation due to the intrinsic amorphous silicon (a-Si:H) layers. During cells manufacturing, the a-Si:H film deposition is simultaneously performed on both c-Si wafer sides, and conse-quently also on the edges of the wafer. However, the wafer edges could result non-passivated in many cases such as the so-called shingling manufacturing route.Moreover, at laboratory level it is quite common to manufacture small area cells from larger wafers. When a silicon edge is left uncovered by cutting, a recombining region is created due to the silicon non-passivated surface. This, in principle, leads to a reduction in the Voc of the cell.Nevertheless, this is not experienced for large area cells cut in half but it is commonly observed that cutting silicon HJ edges results in a lowering in Voc. In this work we have analyzed the correlation between the Voc, the cell area and the recombining surface introduced by cutting the cell into a smaller one. We have monitored the Voc as a function of the cell area during time, and we also have investigated the possibility of a re-passivation of the cell edges by depositing a thick a-Si:H layer after masking the sun exposed cell surface, exploring different deposition conditions to avoid re-annealing of the existing a-Si:H layers.

Crystalline silicon‐based heterojunction (HJ) solar cells are becoming the best choice for manufacturing companies, because of the low temperature processes useful for very thin silicon wafers and the possibility to easily achieve cells efficiencies higher than 22% on n‐type silicon wafers. However, the maximum cell efficiency is still limited by the typical Fill Factor (FF) value of 82%. This issue is due to several factors, some of which are sometimes underestimated, like the base contact. Indeed, a potential mismatch between the work functions of the transparent conductive oxide and the base doped layer can give rise to a small barrier against electrons collection, which is not easy to recognize when the cell FF overcomes 80%. Also a low doping efficiency of the p‐type amorphous layer at the emitter side can negatively affect the FF. In this case, even if high efficiency cells are produced, their full potential is still unexploited. Thus, both selective contacts of the cell, even if apparently optimized to achieve very good results, can hide problems that limit the final cell FF and efficiency. In a previous work, an experimental method and a model to individuate hidden barriers at the base contact on n‐type crystalline silicon‐based HJs have been provided. In this paper, that model is applied to experimental data obtained from the characterization of both commercial and laboratory level HJ solar cells. Moreover, an easy method to recognize the presence of a barrier to the charge transport at the emitter side of the cell is illustrated.

The main objective of the European project AMPERE was the implementation of a 200 MWp fully automated glass/glass bifacial photovoltaic module pilot line based on silicon heterojunction technology. In this work, the results of the compatibility assessment of different commercial encapsulants with the new module design are presented. The study has been conducted by first testing the durability of each encapsulant and its interaction with the interconnected cells. Later the results have been transferred and validated for full size (72cells) modules by an extended and sequential stress testing sequence. The study showed that polyolefin elastomers are more compatible to heterojunction technology than other commercial encapsulants.

AMPERE project, acronym for Automated photovoltaic cell and Module industrial Production to regain and secure European Renewable Energy market, is aimed to the setting-up of an innovative 200 MWp/y full-scale automated pilot line for the production of heterojunction solar cells and modules, with bifacial architecture, in Europe. This work traces the activity of the entire project that led to the rebirth of a new photovoltaic industry lead by Enel Green Power in its production site in Catania-Italy, highlighting its most relevant results in terms of technological and industrial development, economical assessment and market perspectives. The implementation of innovative technologies into these industrial manufacturing lines demonstrates that a larger production of PV products at a competitive Levelized Cost of Electricity (LCOE) at European manufacturer level is possible. Basing on financial estimations and on manufacturing line first results the project delivers the roadmap for the exploitation at GWp level

Perovskite/silicon tandem solar cells represent an attractive pathway to upgrade the market-leading crystalline silicon technology beyond its theoretical limit. Two-terminal architectures result in reduced plant costs compared to four-terminal ones. However, it is challenging to monolithically process perovskite solar cells directly onto the micrometer-sized texturing on the front surface of record-high efficiency amorphous/crystalline silicon heterojunction cells, which limits both high-temperature and solution processing of the top cells. To tackle these hurdles, we present a mechanically stacked two-terminal perovskite/silicon tandem solar cell, with the sub-cells independently fabricated, optimized, and subsequently coupled by contacting the back electrode of themesoscopic perovskite top cell with the texturized and metalized front contact of the silicon bottom cell. By minimizing optical losses, as achieved by engineering the hole selective layer/rear contact structure, and using a graphene-doped mesoporous electron selective layer for the perovskite top cell, the champion tandem device demonstrates a 26.3% efficiency (25.9% stabilized) over an active area of 1.43 cm(2)

One of the most limiting factors in the record conversion efficiency of amorphous/crystalline silicon heterojunction solar cells is the not impressive fill factor value. In this work, with the aid of a numerical model, the ways to enhance the cell fill factor up to 85% are investigated in detail, considering the properties of conventional amorphous-doped films, wider Energy gap layers, and transparent conductive oxide films. The band alignment among the various materials composing the heterojunction is the key to high efficiency but becomes an issue for the solar cell fill factor, if not well addressed. One of the most interesting outcomes of this work is the evidence of hidden barriers arising between the transparent conductive oxide and both selective contacts, due to the mismatch between their work functions. The measurement of light current-voltage characteristics performed at low temperature is proposed as a way to identify the presence of these barriers in efficient solar cells that do not possess high fill factor values. Experimental J-V characteristics compared with numerical simulations demonstrated that the sometimes neglected cell base contact needs instead a more careful consideration. To this aim, a model to predict the presence of a hidden barrier at the base contact that limits the cell fill factor is proposed.

A full-scale pilot line for producing bifacial solar modules based on silicon heterojunction technology was set up as part of the European H2020 AMPERE project. In this study, the measurements from two outdoor test benches were used to evaluate the performance of the new modules under real operating conditions. The performance was benchmarked to that of commercial modules. A new bifacial irradiance model was validated based on the data and used to correct the bifacial gain estimates for differences in rear irradiance between the strings under comparison. The new modules increased the yield by 1-4% compared to the commercial alternatives.

Perovskite/silicon tandem solar cells represent an attractive strategy to push the market-leading crystalline silicon technology beyond its theoretical limit, maintaining low module costs. Record-high efficiency silicon heterojunction cells with a micrometre-sized pyramid textured front-surface hinder high-temperature and low-cost solution processing of the top-cell in a monolithic architecture. We present a mechanically stacked two-terminal perovskite/silicon tandem device, allowing independent fabrication and optimization of the sub-cells, subsequently coupled by contacting the back-electrode of the mesoscopic perovskite top-cell with the texturized and metalized front-contact of the silicon bottom-cell. Our champion device exhibits a stabilized efficiency of 25.9% over a 1.43 cm2 active area, achieved by optically engineering the hole-selective layer/rear-contact structure to minimize the optical losses, and improving the electrical performance with a graphene-doped mesoporous electron-selective layer. This represents a simple path toward fabricating tandem devices overcoming the limit of single junction solar cells and with a competitive levelized cost of energy.

Aim of AMPERE is the setting-up of an European sustainable manufacturing full-scale automated industrial pilot line, to produce bifacial heterojunction technology (HJT) silicon solar cells and modules. In this work we illustrate the state of art of AMPERE project, started in May 2017, focusing on its technical results, industrial and economic sustainability and perspectives on LCOE in the frame of vertical integration along with EGP as its natural end-user. These expected outcomes will be assessed and evaluated as a solid backbone to pave the way to the GW factory scaling up. The decision to accelerate in the project timeframe, within 2019, the installation and start-up of a manufacturing line, leading to a nominal capacity of EGP Catania 3SUN site to 200 MWp, will support the demonstration of the viability of HJT solar module massive production in Europe.

Cu2ZnSnS4 (CZTS) wide-bandgap semiconductor can find a promising application in CZTS/Silicon tandem devices. The connection between the top and the bottom cells requires development of a proper intermediate electrical contact that must exhibit high transparency in the infrared region, chemical stability under thermal treatment and must prevent silicon degradation during the sulfurization processes used for the CZTS growth. In this work we report a first CZTS/Silicon monolithic tandem device with a V-oc = 948 mV and an efficiency of 3.5%, produced using a MoS2/FTO/ZnO intermediate contact. This trilayer needs to be optimized to increase the J(sc) still limited to 6 mA/cm(2).

Earth abundant Cu2ZnSnS4 (CZTS) semiconductor can find a promising application as wide-bandgap top cell absorber in CZTS/Silicon tandem devices. The coupling between the top and the bottom cells in a monolithic device requires the development of a proper intermediate connection able to ensure: (i) high transparency in the infrared region (ii) good electric contacts and (iii) good chemical stability under thermal treatments used for the CZTS growth, in order to prevent elements interdiffusion and silicon degradation. To this purpose, some multilayered structures based on MoS2 and different Transparent Conductive Oxides (TCOs) were tested as intermediate connection in CZTS/Silicon tandem devices. The first working monolithic tandem cell, with open circuit voltage of about 950 mV and an efficiency of 3.5%, was obtained using a MoS2/FTO/ZnO trilayer structure as intermediate contact between the top and the bottom cells. Some limiting factors of this device were addressed and investigated in order to increase the tandem cell efficiency.

An expression for collection efficiency in actual Si solar cells is derived from the expression of Basore for inverse quantum efficiency vs. absorption depth at near-bandgap wavelengths. In the new expression, only internal rear-surface reflectance is an adjustable parameter. The new expression is used in reported actual Si solar cells, where it is compared to different approaches to evaluate collection efficiency including the linear fitting to inverse internal quantum efficiency versus absorption depth. This allows showing experimentally that these approaches are more liable to errors than the proposed expression for collection efficiency.

Indium Tin Oxide (ITO) is widely used in solar cell devices for its excellent electrical and optical characteristics, such as high transparency in the Ultraviolet-Visible range and good conductivity (around 10 4 W -1 cm -1 ). In this work we have compared thin (70-150 nm) ITO layers deposited by Direct Current or Radio Frequency sputtering. We have used different substrate temperatures during film growth and have afterwards thermally annealed the samples at different temperatures up to 300 °C to investigate the effects on the electrical and optical properties of the material. We have found out that the different growth/annealing conditions induce changes in the optical properties of the samples as well as in the conductivity and carrier concentration.

Based on the data in the literature, in highly-doped Si, where Auger recombination predominates, one can observe that, while minority-carrier bulk lifetime is inversely proportional to the square of doping density, diffusivity can be taken as constant. This implies that, at high dopings, diffusion length can be considered as proportional to the reciprocal of doping density. In the present work, we assume that such a dependence of diffusion length on doping holds at lower dopings as well, in the case, where Auger recombination prevails. This allows deriving a very simple expression for Auger lifetime as a function of diffusivity that is used together with a reported expression for radiative lifetime to calculate intrinsic lifetime at all dopings. The new expression for intrinsic lifetime is consistent with reported doping functions for minority-carrier diffusivity and agrees with the data of lifetime for dopings higher than 4x10(17) cm(-3) in both p-type Si and n-type Si. We exploit the relevant theory to show that such results are due to the fact that, at those doping levels, both diffusivity and Auger recombination are enhanced by electron-hole interaction.

We present the exact analytical solution to minority-carrier transport in the dark for non-uniformly doped Si regions in low-level injection, where bulk lifetime is inversely proportional to the square of doping density according to the Dziewior and Schmid model of Auger recombination and diffusivity is constant. The relevant expression for emitter saturation current density, J(0em), can be set as a function of sheet resistance, R-SHEET. Reported measured J(0em)(R-SHEET)curves in n- and p-type metal-coated emitters are matched by the presented J(0em)(R-SHEET)-expression. To this aim, reported doping functions for band-gap narrowing are set as functions of R-SHEET. The application range of the presented solution is checked.

Including Auger-recombination enhancement in the minority-carrier continuity equation and imposing to minority-carrier diffusivity to tend to a constant value allow expressing Coulomb-enhanced (C.E.) Auger lifetime in doped c-Si at room temperature and low-level injection as a function of diffusivity at all dopings. By exploiting reported doping-functions for diffusivity, the new expression for diffusivity-consistent C.E. Auger lifetime is used together with a reported expression for radiative lifetime and constant values for Shockley-Read-Hall lifetime to calculate curves of minority-carrier lifetime and diffusion length vs. doping to be compared to the corresponding curves calculated using a recently reported improved empirical model for C.E. Auger lifetime that does not consider diffusivity.