Thermal evaporation offers a scalable and solvent-free pathway for transitioning perovskite from laboratory prototypes to industrial production, yet it remains significantly underexplored. In this work, we present the first fully solvent-free top cell in a 2-terminal perovskite-silicon tandem solar cell. We systematically explore the structural and morphological evolution of sequentially evaporated perovskite films and the impact of silicon substrate topography on the perovskite film formation. Using in situ X-ray diffraction (XRD), we observed an enhanced conversion of lead halides to perovskite on micro-textured substrates compared with planar substrates. Correspondingly, morphological characterizations revealed a compact layer of lead halides on planar substrates compared with a porous one on textured substrates. Alongside this, an initial layer-by-layer deposition of lead halides is observed, followed by interlayer mixing after adding formamidinium iodide (FAI). These insights advance the understanding of sequential thermal evaporation and enable fully solvent-free perovskite-silicon tandem solar cells with a stabilized power conversion efficiency of 27.0%.

The industrial realization of high-efficiency perovskite/silicon tandem (PST) solar cells hinges on scalable, low-temperature fabrication of complex electron contact architectures. Here, we report a hybrid spatial atomic layer deposition (SALD) and physical vapor deposition (PVD) platform that enables the sequential, vacuum-based deposition of AlOx/C60/SnOx electron contact stacks over G12 wafer formats. The system integrates a custom-designed linear evaporator into a high-throughput SALD reactor, allowing precise control of layer thickness and uniformity. Real-time ellipsometry provides in-line monitoring, revealing growth delays of SnOx on hydrophobic C60. Photoluminescence measurements demonstrate that AlOx passivation significantly enhances quasi-Fermi level splitting. This work establishes a scalable, inline-compatible process for next-generation tandem photovoltaic devices.

Self-assemble monolayers (SAMs) have become state-of-the-art hole-selective contacts for high-efficiency perovskite-based solar cells due to their easy processing, passivation capability, and low parasitic absorption. Nevertheless, for the deposition of SAMs with a monolayer thickness and a high packing density on metal oxide substrates, critical challenges persist. To overcome these, the study focuses on the impact of annealing temperature - an intrinsic yet so far unexplored process parameter - during the formation of SAMs. By performing in situ angle-resolved X-ray photoelectron spectroscopy combined with advanced data analysis routines, it is revealed that increasing the annealing temperature reduces the formed SAM layer thickness from a multilayer stack of approximate to 5 nm at 100 degrees C (conventional temperature employed in literature) to a monolayer at 150 degrees C. Furthermore, denser adsorption of the SAM to the metal oxide surface is promoted at high temperatures, which enhances the interfacial SAM/perovskite passivation quality. With this strategy, a 1.3%(abs) power conversion efficiency (PCE) increment is obtained in fully-textured perovskite/silicon tandem solar cells, with improved reproducibility, and a champion device approaching 30% PCE. This study advances the understanding of SAMs formation and presents a promising strategy for further progress in high-efficiency perovskite-based solar cells.

Within this work, we present key results of the transnational European research project “Bussard”. The aim of this project is the development and evaluation of various innovative approaches for highly efficient cell concepts such as tunnel oxide passivating contact (TOPCon) solar cells considering the whole process chain including front-end, back-end and module processing. We present atomic layer deposition (ALD) as a high-throughput alternative for the deposition of Al2O3 passivation layers on the front side of TOPCon solar cells enabling a substantial reduction of the emitter saturation current density down to j0e = 13 fA/cm2. In the field of metallization, we evaluate and demonstrate three innovative approaches for the fine-line metallization of TOPCon solar cells. In this study we focus on multi-nozzle parallel dispensing, a technology that was developed as an alternative to standard screen-printing metallization and is used for the metallization of TOPCon solar cells for the first time. By optimizing the fabrication process at Fraunhofer ISE, we realize TOPCon solar cells (156.75 mm × 156.75 mm) with a champion conversion efficiency of up to ηmax = 24.2% (independently confirmed by Fraunhofer ISE CalLab PVCells). Finally, we present a comprehensive evaluation of the innovative Tape Solution interconnection concept for TOPCon cells and modules. We demonstrate the feasibility on small-scale and full-format modules and analyze the I–V results as well as cell-to-module (CTM) loss analysis using the simulation tool SmartCalc®. The results are compared to TOPCon modules interconnected via SmartWire Connection Technology (SWCT) and electrically conductive adhesive (ECA).

Solar photovoltaics (PV) is entering a new era of multi-terawatt deployment, with 2 TW already in service and more than 75 TW predicted in many scenarios by 2050. This next era has been enabled by over five decades of cumulative advances in PV module cost reduction, performance and reliability. The current scale of deployment also introduces new needs, opportunities and challenges. In this Perspective we frame a path forwards based on learning, broadly defined as a combination of expansion of knowledge and advances through research and development, experience and collaboration. We discuss historical topics where learning has driven PV deployment until now, and emerging areas that are required to sustain high levels of future deployment. We expect progress to continue in terms of module price, performance and reliability, driven by advances in PV cell and module design, the emergence of tandem devices and increased focus on extending module lifetimes. Large-scale deployment also means large-scale sustainability and responsibility. We therefore posit that additional metrics, such as the impact on global CO2 emissions, resource consumption and design for reuse and recycling, will become increasingly important to the PV industry and provide opportunities for further learning. Solar photovoltaics is entering a multi-terawatt era, driven by decades of cost, performance and reliability gains. In this Perspective Alberi et al. discuss the role of historical and future learning, highlighting the increasing importance of sustainability considerations.

Wide bandgap (Ag,Cu)(In,Ga)Se _2 (ACIGSe) is a viable candidate as top cell absorber in tandem devices. In this work, we investigate monolithic two-terminal ACIGSe-Si tandem cells with a bandgap of 1.5 eV. Our research focuses on the direct preparation of the ACIGSe top cell on the Si bottom cell, the impact of the top cell absorber thickness and the gain through bifacial illumination. Bifacial monocrystalline silicon solar cells with tunnel oxide passivated contacts (TOPCon) are used as bottom cells. Considering that the TOPCon structure allows high temperature treatments without severe device degradation, TOPCon silicon cells are in principle suitable for ACIGSe deposition at evaporation temperatures of approximately 600 °C. Variation of the ACIGSe absorber thicknesses reveals an optimum for low top cell absorber thicknesses. The optimum shifts to thicker absorbers of 1 µ m when operating the tandem device bifacially with back illumination reaching the highest output power of 16.2 mW cm ^−2 with addition rear illumination of 52% of 1-sun illumination. An electro-optical computer simulation supports the experimental outcome.

Perovskite-silicon (Pero-Si) tandem solar cells have made remarkable progress in recent years, achieving certified cell efficiencies of up to 33.9%. However, accurately measuring the efficiency and current density-voltage (JV) curves of these devices poses various challenges including the presence of mobile ions within the perovskite absorber that lead to short- and long-term transient effects. Consequently, both the measurement setup and the preconditioning of the device significantly affect measurement results. This study focuses on enhancing the reliability and comparability of JV and other efficiency measurements for Pero-Si tandem devices through a systematic analysis of the influence of mobile ions, preconditioning and measurement conditions. For the first time, a full opto-electrical simulation model for Pero-Si tandem devices is presented in Sentaurus TCAD, which includes the drift-diffusion of anions and cations and is therefore able to describe short- and long-term transient device effects in state-of-the-art Pero-Si tandem cells. Experimental validation and evidence are given by comparison to in-house Pero-Si tandem cells, as well as Pero-Si mini modules from Oxford PV. We analyze by simulation and experiment how the cell preconditioning at different preconditioning voltages and times impacts the resulting measured tandem efficiency, as well as impact of JV scan times for the measured hysteresis in Pero-Si tandem devices. Furthermore, we demonstrate the impact of current-mismatching conditions on the measured hysteresis of the Pero-Si tandem device and the need of correct spectral irradiance settings during measurements. We showcase that even a very slight variation in short-circuit current density (jsc) around the current-matching point leads to significantly different hysteresis behaviors. With aid of our simulation model, we could attribute this phenomenon to a reverse/forward biasing of the perovskite sub-cell impacting the ion drift depending on the current-limiting sub-cell of the tandem device. Therefore, it is sensible to be aware of the current limiting sub-cell for the comparison of the hysteresis susceptibility of different Pero-Si tandem devices. This study strongly underscores the importance of including the preconditioning and measurement conditions when reporting Pero-Si tandem efficiencies. The findings highlight the urgent need for standardization in the field. This study addresses challenges in accurately measuring perovskite-silicon (Pero-Si) tandem solar cell efficiency and current density-voltage (JV) curves due to mobile ions. A comprehensive opto-electrical simulation model for Pero-Si tandem devices is introduced, considering ion drift effects. Experimental validation reveals the impact of preconditioning, JV scan times, and current-mismatching conditions on efficiency measurements. The study emphasizes the importance of standardization in reporting Pero-Si tandem efficiencies, stressing the need for careful consideration of preconditioning and measurement conditions. image

Multi-junction solar cells are the most famous approach to overcome the power conversion efficiency (PCE) limit of single-junction solar cells. Metal halide perovskite absorber materials offer low-cost fabrication and tunable...

Fully-textured perovskite silicon tandem solar cells merge between a high efficiency potential and compatibility to existing silicon production lines, making them a suitable candidate for wide scale photovoltaic deployment. In this work, we delve in a first step into the dynamics of perovskite crystallization by monitoring the structural evolution from precursor to perovskite phase via in-situ X-ray diffraction, and outline guidelines to obtain highly crystalline perovskite films. Then, we investigate the impact of different process parameters on shaping the final perovskite film properties. Incorporated in a fully-textured tandem architecture, the device delivers 26.7% efficiency. A loss analysis reveals that high series resistance and non-radiative recombination losses at the perovskite/electron transport layer (C60) interface severely limit the performance. We tackle these losses simultaneously by employing a multifunctional perovskite crystallization and surface passivation agent enabling the fabrication of a 30.0% efficient tandem solar cell. Looking one step ahead, experimentally identified solar cell parameters are combined to an opto-electrical simulation model, thus determining a device practical efficiency potential of 39.5% for this tandem solar cell design.

Plasma-Enhanced Chemical Vapor Deposition (PECVD) is an attractive tool for TOPCon production, as it enables uniformly in situ doped amorphous silicon (a-Si) and dielectric layer depositions with high throughput. However, a lean process requires in situ interfacial oxide growth in the same tool. In this work, we use Plasma-Assisted N2O Oxidation (PANO) in an industrial kHz direct plasma reactor (centrotherm c.PLASMA) to grow the oxide and deposit in situ phosphorus doped a-Si(n) as well as SiNx on asymmetric lifetime samples. Before optimization, the oxide thickness is non uniform on the wafer, and we show that it correlates with the passivation, the contact resistivity, and the doping profile in n-type TOPCon test structures. The passivation seems to benefit more from moderate in-diffusion in the case with PANO than in the case with thermal oxidation. This is probably due to enhanced field-effect passivation compensating for lower chemical passivation, which likely results from plasma-induced damage. After studying the influence of PANO process parameters on the oxide thickness and uniformity, we optimize them to obtain a non-uniformity as low as ±2% and a recombination current density down to 2.3 fA/cm² on planar wafers.

Fully textured perovskite silicon tandem solar cells are promising for future low-cost photovoltaic deployment. However, the fill factor and open-circuit voltage of these devices are currently limited by the high density of defects at grain boundaries and at interfaces with charge transport layers. To address this, we devise a strategy to simultaneously enhance perovskite crystallization and passivate the perovskite/C-60 interface. By incorporating urea (CO(NH2)(2)) as an additive in the solution step of the hybrid evaporation/spincoating perovskite deposition method, the crystallization kinetics are accelerated, leading to the formation of the desired photoactive phase at room temperature. With that, perovskite films with large grain sizes (>1 mu m) and improved optoelectronic quality are formed at low annealing temperatures (100 degrees C). Concurrently, remnant urea molecules are expelled at the perovskite surface, which locally displaces the C-60 layer, thus reducing interfacial non-radiative recombination losses. With this strategy, the resulting tandem solar cells achieve 30.0% power conversion efficiency.

Optical losses of perovskite/silicon tandem solar cells can be effectively reduced by optimizing the thin‐film layer thicknesses. Herein, the thicknesses of DC sputtered indium tin oxide (ITO) films, which serve as the front electrode and the recombination layer connecting the subcells, are optimized to reach high transparency and good lateral charge transport simultaneously. Optical simulations of the full perovskite/silicon tandem solar cell stacks are performed to find the optimum recombination and front electrode ITO thicknesses for solar cells as well as modules. Implementation of the optimized 25 nm front electrode ITO thickness in semitransparent single‐junction perovskite solar cells increases the short‐circuit density by 1.5 mA cm −2 compared to the former reference thickness of 75 nm. Combined with an optimized 20 nm recombination ITO layer, high short‐circuit density of 20.3 mA cm −2 is reached in perovskite/silicon tandem solar cell devices, which is the highest reported value for planar front perovskite/silicon tandem solar cells to the best of knowledge. Further interface passivation enables 28.8% power conversion efficiency.

One challenge in thin-film based solar cells, including perovskite-silicon tandem cells, is the defect-free deposition of the thin-film layers. Such defects can result in high local parasitic current losses, that is, local shunt spots. Depending on the nature of the defects, their geometrical distribution can either be microscopic, for example, induced by texture morphology, or macroscopic, for example, induced by particles during processing. Instead of avoiding the defects themselves, so-called shunt-quenching methods have been proposed to mitigate the associated efficiency loss. This work investigates the following recently suggested methods: 1) a deliberate current mismatch; and 2) engineering the resistive properties of the intermediate layers between the subcells to electrically isolate the shunt. A comprehensive 3D device simulation study is presented to quantitatively analyze the (in)effectiveness of these methods. It is found that shunt-quenching by a deliberate current mismatch can only play a minor role in the overall optimization of the current match point. Engineering the resistive properties of the intermediate layers must be generally considered ineffective. It only works for the rather specific case of strong and macroscopically distributed shunts with little cell-to-cell variation and only if some further requirements of the cell design are met.

Silicon solar cells with both-side full-area passivating hole and electron contacts are viable candidates for application as bottom cells in tandem architectures. In this contribution, cells with poly-Si based contacts at both sides are investigated as a potential upgrade to the emerging i-TOPCon single junction devices featuring a passivating contact (poly-Si(n)/SiOx) only at the rear side and an alternative to the SHJ technology featuring a-Si based full-area passivating hole and electron contacts. We show that a higher thermal budget is needed to mediate between poly-Si(p)/SiOx hole and poly-Si(n)/SiOx electron contact when the same thermal interfacial SiOx is applied. This is addressed by using a PECVD oxide that is adapted to the needs of the hole and/or the electron contact. We present a proof-of-concept poly-Si(n)/SiOx/c-Si/SiOx/poly-Si(n) device with emphasis on a lean process flow. An all-PECVD process sequence for the hole contact, i.e., plasma oxides+i/p-a-Si deposited at 200°C in the same chamber was applied. With co-annealing of the contacts, no additional hydrogenation, and no edge insulation step, we observe no shunting and obtain efficiencies of up to 20.8% for M2 size cells, so far.

Both-sides TOPCon solar cells are an interesting candidate for a highly efficient and thermally robust Silicon (Si) bottom cell for tandem devices, such as Perovskite-Si solar cells. However, preparation of p-type TOPCon on a textured surface is necessary which is particularly challenging. This work aims to gain a deeper understanding of the limiting factors and thereby optimize the SiOx/poly-Si(p) contact to close the gap to its n-type counterpart. Using symmetrical lifetime samples, we first show that a high level of surface passivation can be achieved using thermally grown interfacial oxides of different thicknesses. The samples strongly benefit from an effective thermal activation of hydrogenation by means of fast-firing. Thus, a recombination current density J0s as low as 23.4 fA/cm² was achieved for p-type TOPCon on textured surface featuring an in situ Boron-doped poly-Si layer prepared by plasma enhanced chemical vapor deposition (PECVD). Moreover, we show that the passivation quality strongly depends on surface morphology. Smoothening the random pyramids’ valleys and – what is more – the tips has a positive impact on the surface passivation.

Optimally enhancing the performance of perovskite silicon tandem solar cells comes with accurate identification of loss origins in the device in combination with optoelectrical device simulations assessing the respective efficiency gains to prioritize optimization pathways. Herein, various characterization methods, namely, spectrally resolved photoluminescence (PL), transient‐PL, PL‐based implied open‐circuit voltage (i V OC ) imaging, spectrometric characterization, and Suns‐ V OC measurements are combined to quantify current density–voltage ( jV ) photovoltaic metric losses of a fully‐textured perovskite silicon tandem solar cell (26.7% efficiency). The extracted device characteristic parameters are then used as a reference for the comprehensive optoelectrical Sentaurus simulation model which precisely reproduces the experimentally obtained optical and electrical solar cell characteristics, considering mobile ion dynamics. Subsequently, starting from the current device design, the authors alleviate one step at a time the loss constraints and show the impact of each loss channel on the efficiency, identifying the three major ones to be at the: 1) perovskite/C 60 interface (−4.6% abs ) , 2) the series resistance (−2.9% abs ), and 3) light management (−2.1% abs ), which limit the V OC , fill factor, and j SC of the device, respectively. Furthermore, it is demonstrated that a practical efficiency potential of 39.5% can be regarded as a practical limit for the presented tandem device architecture.

Passivating contacts based on poly‐Si/SiO x structures also known as TOPCon (tunnel oxide passivated contacts) have a great potential to improve the efficiency of crystalline silicon solar cells, resulting in more than 26% and 24% for laboratory and industrial cells, respectively. This publication gives an overview of the historical development of such contact structures which have started already in the 1980s and describes the current state‐of‐the‐art in laboratory and industry. In order to demonstrate the great variety of scientific and technological research, four different research topics are addressed in more detail: (i) the superior passivation quality of TOPCon structures made it necessary to re‐parametrize intrinsic recombination in silicon, (ii) the control of diffusion of dopants through the intermediate SiO x layer is essential to optimize passivation and transport properties, (iii) single‐sided deposition of the poly‐Si layer would reduce process complexity for industrial TOPCon cells, and (iv) silicon‐based tunnel junctions for perovskite–silicon tandem cells can be fabricated using the TOPCon technology.

In this work, we present cost-effective, solution-processed, self-assembled organic materials for enhanced charge carrier selectivity for crystalline silicon (c-Si) heterojunction (SHJ) solar cells. Charge transport properties of two different phosphonic acid-based self-assembled molecules, 1H,1H,2H,2H-Perfluorooctanephosphonic acid (FOPA) and [2-(9H-Carbazol-9-yl)ethyl]phosphonic acid (2PACz), are investigated. Interface barrier height modification is achieved by utilizing FOPA and 2PACz between c-Si and the metal electrode at electron-selective contacts. These molecules are applied as dopant-free electron-selective contact in SHJ solar cells. Moreover, the thermal stabilities of organic layers are investigated. A promising efficiency of 16.5%, which is stable upon annealing at 200 degrees C is achieved for SHJ solar cell with FOPA electron-selective contact.

This article reports on the reduction of indium consumption in bifacial rear emitter n-type silicon heterojunction (SHJ) solar cells by substituting the transparent conducting oxide (TCO) indium tin oxide (ITO) with aluminum doped zinc oxide (AZO). AZO, ITO, and stacks of both TCOs are sputtered at room temperature and 170 °C on both sides of SHJ solar cells and glass samples. The short circuit current density ( JSC ) of AZO SHJ cells is lower than that of ITO-based cells, possibly due to a smaller optical band gap E G = 3.35 eV of AZO in contrast to EG = 3.71 eV for ITO, which could lead to stronger parasitic blue absorption for AZO cells. Series resistance R S of pure AZO SHJ solar cells is high mainly due to high contact resistance R C between silver (Ag) metallization and AZO and high R C between amorphous silicon (a-Si) and the transparent AZO with low electron density n e . Using ITO a-Si -AZO-ITO Ag stacks, which saves about 50% of ITO, enables RS values comparable to the ITO reference group, resulting in the same efficiency as the pure ITO cells. By replacing ITO a-Si with a high ne AZO a-Si the lowest RS is achieved. This AZO a-Si -AZO-ITO Ag structure saves about 70% ITO. Damp heat tests on cell and glass samples reveal a clear advantage of TCO stacks over AZO single layers.

The efficiency of perovskite/silicon tandem solar cells has exceeded the previous record for III-V-based dual-junction solar cells. This shows the high potential of perovskite solar cells in multi-junction applications. Perovskite/perovskite/silicon triple-junction solar cells are now the next step to achieve efficient and low-cost multi-junction solar cells with an efficiency potential even higher than that for dual-junction solar cells. Here we present a perovskite/perovskite/silicon triple-junction solar cell with an open circuit voltage of >2.8 V, which is the record value reported for this structure so far. This is achieved through employing a gas quenching method for deposition of the top perovskite layer as well as optimization of interlayers between perovskite subcells. Moreover, for the measurement of our triple-junction solar cells, precise measurement procedures are implemented to ensure the reliability and accuracy of the reported values.