ABSTRACT This work is the first part of three studies dealing with the degradation of crystalline Si‐based solar modules depending on the chosen material combination, whereby the focus of this work is on encapsulant degradation. Within the paper, solar modules based on ethylene‐vinyl acetate (EVA) copolymer encapsulant and polyolefin elastomer (POE) encapsulant with different rear side encapsulations were artificially aged with UV irradiation (76.6 W/m 2 between 280 and 380 nm) in combination with 60% relative humidity at 85°C. In situ moisture measurements and simulations of oxygen diffusion were used to show how stressors are distributed in the module. Additive and polymer degradation was analyzed by the Fourier transform infrared spectroscopy (FTIR), Orbitrap mass spectrometry, and electron paramagnetic resonance (EPR). This approach made it possible to determine the degradation of the encapsulants in a spatially resolved manner depending on the presence of stressors and the consumption of additives. The findings reveal that degradation is heavily influenced by the microclimate within the module, which itself is affected by the material combinations used. It is shown that oxygen has a major influence on the degradation of POE, as it is essential for the formation of hydroperoxides. Furthermore, it becomes clear that EVA does not necessarily have to be inferior to the novel POE encapsulants if it is combined with the right rear side encapsulation.

ABSTRACT Quantum photonic integrated circuits (QPICs) are a promising platform for scalable quantum technologies. A major outstanding challenge is the efficient interconnection of diverse quantum photonic components, where optical losses must remain below the ∼10% threshold required for advanced quantum applications. In this paper, the optical coupling between GaAs single‐photon sources and a low‐loss SiN interposer is investigated, where reliable high‐efficiency transitions have not yet been achieved. To address this, a fully numerical framework is introduced for the optimization of waveguide mode couplers that directly incorporates experimentally characterized fabrication variations critically impacting performance, including waveguide misalignment, width deviation, and sidewall roughness. Using this approach, low‐loss GaAs/SiN transitions are designed and experimentally demonstrated with reproducible coupling efficiencies of –0.43 dB ± 0.14 dB. These results establish a viable path toward low‐loss heterogeneous QPICs tailored to advanced quantum applications.

Backside irradiance modelling for photovoltaic (PV) modules is not simple and straightforward as it highly depends on the situation of an actual system. In addition, the irradiance conditions can change from one side of a PV system to the other due to the reflections from the ground or surroundings. Currently, all available models are based on analytical methods. Here, we present a new empirical model for backside irradiance for fixed PV systems modelled by a Gaussian function on the backside irradiance share and compare the results with an analytical model. Furthermore, we have applied different backside irradiance calculations to a PV performance rating model and compared the results. Our calculations, verified with the data from three different locations in Europe, have shown that for common PV systems, where the backside irradiance share is relatively low, annual PV performance calculations can be performed with a fixed backside irradiance share value.

Using advanced optical modelling, we quantify how sinusoidal corrugation and emitter dipole orientation jointly govern light extraction from OLED thin-film stacks into a glass substrate for red, green, and blue emission. Irrespective of emission colour, the corrugation aspect ratio (AR = height/period) is the dominant geometric parameter controlling extraction, with absolute period and height playing secondary roles, as periods of 600-1000 nm deliver similar gains across all colours. Extraction peaks at AR approximate to 0.2 for predominantly horizontal dipoles, AR approximate to 0.5 for vertical dipoles, and AR approximate to 0.3 for isotropic orientations. For the isotropic case, extraction improves by up to 40%, 34%, and 20% relative to flat red, green, and blue devices, respectively. Absorption analysis attributes the principal gains to suppression of surface-plasmon-polariton losses of vertical dipoles, supported by local dipole reorientation, waveguide disruption, and scattering. Because practical texturing can alter dipole orientation, optimum conditions must be re-evaluated; if orientations follow the sinusoidal profile, an AR of approximately 0.2-0.3 is favoured for isotropic to moderately horizontal orientations, whereas higher ARs benefit strongly vertical orientations. The results provide guidelines for co-optimising corrugation geometry and dipole orientation for high-efficiency OLEDs.

The long-term stability of more than 500 FACs perovskite solar cells has been systematically investigated under various conditions. We first analyze resilience to moisture and show that with the 30 nm Al2O3 capping, we can perform long-term tests in air and eliminate moisture-related degradation. In the long-term MPP tracking tests, we then confirm that light is the driving degradation contributor by performing cyclic tests and testing under different light intensities. Visual changes of the perovskite absorber during the testing and spatial and spectral photoluminescence measurements reveal that phase segregation and the perovskite/C60 interface are the main culprits for degradation, while the perovskite degrades faster in electrically inactive areas. We thus show that by removing bromide ions from the FACs composition, cell stability, evaluated by the t80 lifetime, can improve 5-fold in the best case and that there is a linear correlation between t80 time and bias voltage during stability tracking. By testing a large number of samples (>500), we show with statistical relevance that long-term stability measurements show significantly higher spread (both batch-to-batch and intrabatch) than J-V measurements.

Indoor photovoltaics harvests energy from light available inside homes and buildings for powering the Internet of Things, wireless sensors and consumer and medical electronics. A major challenge in this field is a lack of standardized testing conditions. Here a team from more than 60 research institutions and companies proposes best practices for evaluating indoor photovoltaic performance and establishing baseline stability tests. We base these recommendations on recent experimental data, published literature, practices used in academic and industrial settings, technical specifications from standards organizations, lighting databases and existing regulations. We outline procedures that begin with the recommendation of a single artificial light source, followed by guidance on setting up measurement systems and a step-by-step guide for conducting measurements and tests. These procedures are consolidated into three checklists. Our aim is to promote accurate measurement of laboratory and commercial solar cells and modules under indoor lighting, facilitating comparability across academia and industry worldwide. A major challenge for indoor photovoltaics is the absence of harmonized testing protocols, standards, and shared performance benchmarks. This Consensus Statement outlines recommended practices for testing and reporting device performance, power, efficiency and stability.

The effect of Parylene capping on perovskite solar cells has been tested by its deposition on top of FACs perovskite devices, already capped with 30-nm-thick Al2O3, in three different thicknesses: 2, 5, and 15 mu m. The cells were tested against ingress of water, in damp-heat chamber and long-term maximum power point operation. Devices immersed in water and tested in the damp-heat chamber were regularly measured under a sun simulator to monitor their performance, in addition to visual comparison. In all tests, Parylene-capped cells outperformed the reference without Parylene, clearly demonstrating the beneficial effect of Parylene. In the long-term stability test in air without additional encapsulant, the perovskite solar cell's t 80 lifetime (time till 80% of initial performance) was tripled in the case of 5-mu m-thick Parylene.

Perovskite solar cells have emerged as leading candidates for low-power indoor energy harvesting due to their high efficiency in indoor lighting conditions and simple low-cost fabrication. However, long-term stability of the perovskite technology remains a critical barrier to widespread deployment. In this study, we evaluate the long-term performance of lab-scale perovskite solar cells deployed in a realistic indoor environment over a 2.5-year period using self-powered Bluetooth Low Energy monitoring devices. Sixteen small-area solar cells were monitored in different indoor locations together with air relative humidity, temperature, and irradiance. The effect of standardized and different real-world indoor light sources to the cell conversion efficiency was analyzed, revealing a discrepancy of up to 56%, when using photometric instead of radiometric units as a reference light intensity. Lifetimes of the sixteen cells ranged from 70 to 522 days, highlighting broad variability in stability, with an observable correlation to actual air relative humidity. Despite significant daily and seasonal fluctuations in cell output performance, we demonstrate that approximate device lifetimes can still be reliably filtered and extracted, even if photometric data is used as a reference light intensity.

A damage analysis was conducted on photovoltaic modules with identical bill of materials exposed to different climates: Cfb moderate and Af tropical, according to the Köppen-Geiger climate classification. The combination of high temperature, relative humidity, and high ultraviolet (UV) radiation was the cause of severe degradation for the modules exposed to tropical climates (TR), whereas the module exposed to a moderate climate did not experience a significant loss in performance. The modules installed in TR, on the contrary, showed significant power degradation after approximately 8 years of exposure, primarily attributed to acetic acid-related degradation modes. Encapsulant samples were extracted from the selected modules and characterized to determine changes in chemical structure, thermal stability, and consumption of additives and stabilizers. The results of qualitative additive analysis showed that the UV absorber was no longer detectable in the front encapsulant extracted from modules exposed in TR. The consumption of the stabilizers was considered as the main cause of reduction of molar mass. The presence of acetic acid was evident in both electroluminescence images and ion chromatography results. While differential scanning calorimetry successfully detected a reduction in molar mass, thermogravimetric analysis, and infrared spectroscopy proved unsuitable for identifying chain scission phenomena.

Near‐infrared perovskite light‐emitting diodes (PeLEDs), with four perovskite (PK) layer thicknesses and optional micro‐textured light management (LM) foil, are fabricated to evaluate their effects on light outcoupling efficiency. Devices with a 70 nm thick PK exhibit highest external quantum efficiencies (EQE), compared to those with thinner or thicker PK layers. The PK thickness influences the overall thin‐film stack and, consequently, the light outcoupling. LM foils significantly improve light outcoupling across all devices, with the thickest PK layer (160 nm) benefiting the most (60% increase), while the thinnest (40 nm) sees the least improvement (30%). Measured trends align well with optical modeling results, further highlighting the impact of sample holder design and pixel position on results. Theoretical optimization of PK thickness indicates unique optimal values for devices with or without LM foils. For devices incorporating LM foils, simulations predict an optimal PK thickness of 80 nm and an EQE of 27%. In contrast, for devices without LM foils, the optimal PK thickness of 60 nm corresponds to simulated EQE of 17%. In all cases, LM foils significantly enhance light outcoupling from bottom‐emitting PeLEDs while emphasizing the necessity to include LM foils in the thin‐film layer stack optimization process.

Top-performing single-junction and two-terminal tandem devices that include at least one polycrystalline cell are compared with each other and their ideal limits. The parameters of open-circuit voltage, short-circuit current, and fill-factor are individually compared to the Shockley-Queisser limit to investigate where different technologies have room to improve. Technologies, such as silicon and cadmium telluride have the most room for improvement in open-circuit voltage currently utilizing 87% and 81% of their maxima, respectively. Detailed diode and fill-factor loss analysis is presented for single-junction devices to give further insight on how they compare and where efficiency is lost. Single-crystal technologies demonstrate a fill-factor closer to the Shockley-Queisser limit than polycrystalline devices. The high diode quality factor of polycrystalline devices is the leading cause of the decreased fill-factor. Similar analysis on tandem cells with at least one thin-film cell shows that although their efficiency exceeds that of the single-junction cells, the fraction of their ideal efficiency is smaller. By comparing parameters to the Shockley-Queisser limit, it becomes clearer where certain technologies have the potential for improvement.

Predicting the energy output of a bifacial photovoltaic (PV) module is usually not as straightforward as for a monofacial module. The problem usually lies in the estimation of the back-side irradiance which strongly depends on the mounting conditions, tracking or fixed positioning and variable ground albedo. We developed a new direct-diffuse power rating model for predicting the energy yield and performance ratio of bifacial photovoltaic modules (DDPRbifi). The model was validated on 16 bifacial monocrystalline silicon modules of three silicon PV technologies (SHJ, IBC, TopCon) and monitored at four different locations in Europe. The new model shows the best accuracy on all PV modules regardless of the module technology and monitored location. On average, the discrepancy between the simulated and measured performance ratio of the observed modules is around 2 %.

Quantum photonic integrated circuits (QPICs) offer a promising path toward scalable quantum technologies. QPICs rely on the integration of many quantum photonic components and interconnecting optical waveguides for generation, manipulation, and detection of single photons. A key challenge in QPICs is the management and minimization of optical losses, which is particularly critical for single-photon applications. In this paper, we investigate optical propagation losses in strip waveguides within suspended gallium arsenide (GaAs) platforms, which can directly host deterministic single-photon sources but suffer high scattering-related losses. We systematically analyze different scattering loss contributions by investigating four key waveguide perturbation types: sidewall roughness, top surface roughness, surface particles, and suspension tethers. Our approach combines rigorous 3D finite-difference time-domain (FDTD) simulations with experimental measurements to decouple and quantify individual contributions to the total propagation loss. We study two suspended GaAs platforms operating at different wavelengths: an established 930 nm platform and an emerging 1300 nm platform in the telecommunication O-band. Based on our findings, we identify the dominant scattering loss mechanisms and propose novel design-time guidelines and concrete strategies to reduce the main loss contributions by factors of 2.5-5. These improvements are crucial for enabling complex QPICs directly within the native platform of the single-photon source, supporting advances in integrated quantum technologies.

Van der Waals materials exhibit a variety of states that can be switched with low power at low temperatures, offering a viable cryogenic 'flash memory' required for the classical control electronics for solid-state quantum information processing. In 1T-TaS2, a non-volatile metallic 'hidden' state can be induced from an insulating equilibrium charge-density wave ground state using either optical or electrical pulses. Given that conventional memristors form localized, filamentary channels which support the current, a key question for design concerns the geometry of the conduction region in highly energy-efficient 1T-TaS2 devices. Here, we report in operando micro-beam X-ray diffraction, fluorescence, and concurrent transport measurements, allowing us to spatially image the non-thermal hidden state induced by electrical switching of 1T-TaS2. The results reveal a long-range ordered switching region that extends well below the electrodes, implying that the self-organized, collective growth of the hidden phase is driven by charge rearrangement and concomitant lattice strain. Our combination of techniques showcases the potential of non-destructive, three-dimensional X-ray imaging to study bulk switching in microscopic detail, exemplified here by electrical control of the charge-density wave state of a van der Waals material.

Triple-junction solar cells theoretically outperform their double-junction and single-junction counterparts in power conversion efficiency, yet practical perovskite-perovskite-silicon devices have fallen short of both theoretical limits and commercial targets. To address surface defects in the top perovskite junction, we introduce a piperazine-1,4-diium chloride treatment, which replaces less stable lithium fluoride. For interfacing the top and middle perovskite junctions, we optimize the size of gold nanoparticles deposited on atomic layer-deposited tin oxide for best ohmic contacting with minimal optical losses. Applying these strategies, our champion 1-cm2 triple-junction cell achieved a third party-verified reverse-scan power conversion efficiency of 27.06% with an open circuit voltage of 3.16 V. Scaling up to 16 cm2, the device produced a certified steady-state power conversion efficiency of 23.3%. Device longevity also improved by eliminating methylammonium and incorporating rubidium into the perovskite bulk alongside the piperazine-1,4-diium chloride surface layer. An encapsulated 1-cm2 cell retained 95% of its initial efficiency after 407 h at maximum power point and passed the IEC 61215 thermal cycling test. These results represent advancements towards efficient and stable perovskite-perovskite-silicon triple-junction solar cells.

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.

With continuous progress in photovoltaic (PV) technology, the conversion efficiency of commercial PV modules is steadily increasing well above 20 %, even exceeding 24 %. Such high-efficiency (HE) PV modules typically exhibit long free-carrier lifetimes, resulting in high diffusion capacitances. For routine field testing, technicians rely on fast, affordable and portable IV curve scanners, which typically employ the load capacitor scanning method. When applied to HE PV modules with high internal capacitance, this method frequently leads to IV curve distortion, resulting in a significant underestimation of the measured maximum power point (MPP). In this paper, we propose a novel extrapolation technique that corrects the distortion of the measured IV curve through two consecutive IV scans using two different load capacitors. The extrapolation algorithm uses a dynamic electrical model of the whole system, including the PV module and the measurement setup, to compensate for the effect of the PV module’s capacitance on the acquired IV curve shape. It extracts two free parameters related to series resistance and the lifetime of the minority carriers that give the best match between the two extrapolated IV curves. We validated the method on four different state-of-the-art HE PV modules (HIT, TOPCon, IBC, and PERC), reliably reducing the MPP error from the initial up to 4 % to less than 1 %.

Insights are reported from a 4-year outdoor study in Berlin using encapsulated p-i-n perovskite solar cells with the structure ITO | 2PACz | Cs0.15FA0.85PbI2.55Br0.45 (bandgap of 1.65 eV) | C60 | SnO2 | Cu. Peak summer performance showed little to no degradation during the first two summers and only approximate to 2% absolute drop in outdoor power conversion efficiency from the first to fourth summer. Despite good stability, the devices exhibit significant seasonality, with winter performance up to 30% lower than in summer during the first year, increasing with aging. The factors contributing to this seasonality are separated into four categories: I) solar spectrum, II) device temperature, III) maximum power point tracking losses, and IV) metastability effects. Among these, metastability - particularly light-soaking behavior - is the largest contributing factor that sets perovskite technology apart from conventional photovoltaics. It was found that in cold, low-light winter conditions, voltage gains from light-soaking remain unsaturated, leading to reduced performance. Full saturation requires more than 24 h of continuous illumination, indicating that device performance depends on more than a single diurnal cycle. This comprehensive analysis highlights the complexity of seasonal behavior and the importance of long-term, real-world testing for accurate forecasting of perovskite photovoltaic energy yield.