Selenium has improved carrier lifetime and luminescence in CdSexTe1-x/cadmium telluride (CdTe) bi-layer absorbers. Without a CdTe layer, uniform bandgap, without any intentional doping (undoped), CdSeTe-only (or CST-only) absorbers exhibited higher external radiative efficiency and carrier lifetimes compared to bi-layer absorbers. However, this did not translate into device performance. This has been attributed to poor hole mobility in the undoped CdSeTe-only absorber due to the presence of hole traps. In this study, we demonstrate that the limited device performance stems from the n-type nature of undoped CdSeTe-only absorber within p-type device architecture. A significant improvement in power conversion efficiency from <5% to 13.4% was achieved by reducing the absorber thickness to less than one micron, one of the highest reported for this technology. Poor device performance in undoped thicker absorbers is attributed to limited hole (minority carrier) diffusion. Through solar cell capacitance simulator (SCAPS) modeling, hole diffusion length in these absorbers, with electron concentration of 3 × 1015 cm−3 (extracted from C–V measurement), was estimated to be in the range of 0.5–0.9 μm.
The core-shell nanorod architectures provide an ideal platform for integrating the near-infrared response of semiconductor quantum dots (QDs) with perovskites, owing to their superior light harvesting capability and directed charge transport characteristics. However, the heterogeneous interfaces within such hybrid systems inevitably introduce detrimental defects that exacerbate carrier recombination losses. Herein, we report a synergistic passivation strategy employing potassium iodide (KI) to simultaneously modulate the bulk crystallization quality of MAPbI3 and the interfacial defect states of lead sulfide QDs. The influence of KI concentration ([K+] / ([MA+] + [K+]) = 0.05–0.20) on the structural, optical, photovoltaic, and carrier dynamic properties of the hybrid nanorod arrays was systematically investigated. The incorporation of KI yields dual positive effects: on the one hand, it optimizes the crystallization kinetics of the perovskite, promoting enlarged grain size (increasing from 209 to 235 nm in diameter) and reduced Urbach energy (from 0.0907 to 0.0825 eV), thereby effectively suppressing nonradiative recombination in both the bulk and at the interfaces. On the other hand, K+ ions accumulate at interfaces to neutralize charge accumulation, while I− ions fill iodine vacancies and passivate undercoordinated Pb2+ sites, leading to significantly enhanced interfacial charge extraction efficiency with the charge transfer resistance Rct decreasing from 314.9 to 54.35 Ω. Consequently, at [K+] / ([MA+] + [K+]) = 0.20, the optimized device achieves a power conversion efficiency of 10.24% with a Voc of 0.837 V and a Jsc of 19.42 mA/cm2, representing a substantial improvement over control devices without KI. This work demonstrates an effective approach for the synergistic regulation of bulk and interfacial defects via alkali metal halides, offering new insights for the design of high-efficiency near-infrared-responsive perovskite–quantum dot hybrid photovoltaic devices.
The current energy crisis in Europe demands more renewable energy installation. Looking into the photovoltaic (PV) installations in Germany and The Netherlands, rooftop installations dominate about the share of 45% and 80% of the installations in these countries, respectively. However, rooftops have elements, such as chimneys and antennas, which can cast shadows leading to a drastic energy loss. Typical PV modules have three bypass diodes per module protecting the strings. In extreme cases, only 5% shading of the module area can lead to a total shutdown of the PV module by triggering the bypass diodes. Therefore, AESOLAR has developed a shade-resistant and hot-spot-free PV module to address this challenge and maximize the energy yield in a limited area. The PV module has integrated bypass diodes for each solar cell, showing up to 45% more energy yield than a similar standard module under partial shading conditions. In this work, we analyze and compare the indoor characterization and the outdoor energy yield of the shade-resistant and standard PV modules of AESOLAR that are made from a similar bill of materials under partial shading conditions. The results show a significant advantage in yield production compared to the standard module.
Perovskite/silicon tandem solar cells (PSTSCs) have attracted significant attention in the photovoltaic field because of their excellent power conversion efficiency. However, the inherent instability of PSTSCs has led to a mismatch between existing testing standards and accurate performance evaluation. Although preconditioning brings the cells close to steady-state prior to measurements, specific preconditioning methods remain undefined. In this study, we systematically investigated the effects of light-soaking preconditioning (LSPC) of PSTSCs under open-circuit, short-circuit, and maximum power point (MPP) conditions on their electrical performance parameters. The results showed that LSPC under open-circuit conditions caused an initial improvement in efficiency, followed by continuous degradation, and short-term stabilization did not guarantee sustained performance stability. Preconditioning under short-circuit conditions resulted in a significant decline in cell performance, suggesting that this condition was unsuitable for preconditioning. In contrast, preconditioning under MPP conditions enabled both unencapsulated and encapsulated cells to achieve stability, with efficiency fluctuations less than 2%. Moreover, the efficiency values obtained from reverse I–V scans following MPP preconditioning were consistent with those monitored by maximum power point tracking (MPPT). On the basis of these findings, an efficient and reliable measurement protocol for PSTSCs was proposed: LSPC under MPP conditions for at least 10 min, followed by I–V scanning. This protocol allowed quick and accurate determination of the performance parameters of PSTSCs, providing guidance for standardized characterization of PSTSCs.
The growing adoption of electric vehicle (EV) car-sharing, while contributing to reduced traffic congestion and urban pollution, still presents concerns related to energy supply. Since most grid electricity is still fossil-based, global environmental benefits remain limited. Integrating photovoltaic (PV) and battery energy storage systems (BESS) into EV charging hubs (CH) offers a promising solution. However, optimal system sizing is critical to balance energy benefits and cost-effectiveness. This study proposes a multiobjective optimization method to determine the optimal size of PV-BESS systems integrated with an EV CH, maximizing energy self-sufficiency while minimizing annual total cost. To enhance battery lifetime estimation, a semiempirical battery degradation model is developed. The method is evaluated using the power demand profile of a real-world CH in Bologna. A multicountry analysis across six European nations, which includes Spain, Denmark, Italy, Germany, France, and The Netherlands, assesses how varying solar radiation and electricity costs affect system performance. Results show that self-sufficiency ranges from 51% in Denmark to 72% in Italy and Spain. The optimally sized PV-BESS configuration is economically advantageous for all countries except Denmark, and, in general, pursuing higher self-sufficiency levels leads to exponentially increasing costs, revealing diminishing economic returns.
We report simple and potentially low-cost techniques for creating high-quality n-type gallium arsenide (GaAs) and GaAs p/n junctions and fabricate GaAs p/n junction solar cells. Detailed-balance modeling suggests that 20% AM1.5G efficiency p/n homojunction devices may be possible if the surface doping concentration can be limited to values less than similar to 5 & times; 10(19) cm(-3). Our process exploits an open-tube, vapor-phase, deposition-free, zinc diffusion technique for forming p-type layers in melt-grown n-GaAs substrates that results in sheet resistances less than 1 k Omega/square. In addition, we have improved the minority carrier diffusion lengths of melt-grown GaAs from less than one micron to over five microns using an open-tube, vacuum-free, annealing process which reduces the density of EL2 midgap defects. Finally, we have combined these advances to fabricate epitaxy-free, GaAs solar cells with a validated AM1.5G efficiency of 15.3%.
This article investigates the qualification of photovoltaic micromodules intended for energy harvesting in Internet-of-Things systems, with emphasis on the degradation mechanisms induced by accelerated environmental aging typical of tropical conditions. This study employs multiple complementary characterization techniques-including pulsed current-voltage measurements, electroluminescence imaging, and impedance spectroscopy-combined with multidomain statistical analysis to support decision-making regarding acceptance criteria and failure mode clustering. The work addresses a regulatory gap affecting photovoltaic devices below 5 Wp, a class of modules whose deployment is rapidly expanding in remote, autonomous, and low-power Internet of Things applications, yet remains largely unsupported by certification standards. Together, these procedures establish a unified methodology that integrates electrical, structural, and statistical perspectives, forming a robust analytical foundation for qualification and degradation assessment, acceptance criteria definition, and comparative analysis of PV micromodules.
The field performance of bifacial photovoltaic (PV) modules is influenced by both the ground reflection spectrum and the irradiance distribution on the backside surface. The reflection spectrum is dependent on various factors, including air mass and ground surface type, which complicates its evaluation. In this article, a simplified yet accurate reflection spectrum model based on readily available meteorological parameters is proposed and introduced to calculate the reflected solar spectrum for engineering applications. The impact of the reflection spectrum on the performance of bifacial modules is analyzed and quantified using the spectrum mismatch factor, which measures the degree of deviation between the actual and standard spectra. In addition, a calculation method for the output power of the module is introduced, incorporating the view factor model for backside irradiance. Experimental designs conducted on grassland, soil, and concrete demonstrate the accuracy and applicability of both the reflection spectrum model and the power calculation method. The results indicate that in all three scenarios, the reflection model demonstrates high accuracy, with an average error within 10%. After correction with the spectral mismatch factor, the average accuracy of total power prediction for bifacial modules in three scenarios increased from 91.81% to 96.41%; compared with the traditional fixed broadband reflectance method, the relative errors of power prediction in the three scenarios were reduced from 14.75%, 14.68%, and 5.21% to 2.67%, 1.90%, and 1.44%, significantly improving prediction accuracy and enhancing the fault diagnosis capability in intelligent operation and maintenance of PV systems.
Since its first edition in 2008, the Metallization and Interconnection Workshop for Solar Cells (MIW) has provided a forum for experts in these fields to exchange and discuss. The latest 13th edition of MIW workshop took place on 20th and 21st of October 2025 in Berlin, Germany. In this article as an opening to the special issue of IEEE Journal of Photovoltaics we summarize the highlights of presentations as well as provide a glimpse into the emerging trends based on survey completed by the participants.
This case study investigates mono-crystalline silicon modules from underperforming portions of a utility-scale photovoltaic power plant. Field-collected I-V curves and electroluminescence imaging suggested that increased series resistance was a primary factor driving module degradation. Selected modules were removed from the field for further analysis, including incremental damp heat accelerated testing, which confirmed a progression in series resistance degradation. Two distinct cell degradation behaviors became apparent during the investigation. Cross-sectional scanning electron microscopy (with elemental analysis) and scanning spreading resistance microscopy identified key differences between the two degradation mechanisms, primarily grid finger width and contact resistance. Additionally, the study highlights the reliability implications of retest requirements in International Electrotechnical Commission 61215 for material changes and how they may have mitigated the degradation observed at this site.
Lamination-free minimodules are constructed with silicon solar cells between glass sheets and an edge seal of polyisobutylene and silicone. These samples are stressed using a repeated sequential testing sequence including ultraviolet-containing simulated solar spectrum light exposure at elevated temperature, damp heat, humidity freeze, and thermal cycling adapted from the International Electrotechnical Commission (IEC) TS 63209-2:2022. The minimodule performance throughout the stressing is characterized by flash testing and electroluminescence imaging. Results are compared to conventional laminated minimodules using the same type of solar cells. The lamination-free minimodules experience up to 8% power loss compared to roughly 3% for the laminated versions. However, those losses, dominated by current and fill factor, are caused by glass soiling and busbar ribbon separation on the cells. When glass is replaced and the stressed cells are contacted with probes bypassing the delaminated ribbons, the initial performance is recovered, and overall losses of the lamination-free samples become negligible.
Floating photovoltaic (FPV) systems have gained attention worldwide due to their potential gains in generation, land saving, and water evaporation reduction. However, experimental data from installed FPV plants operating under high irradiance and ambient temperature remains scarce. Our study presents an experimental assessment comparing FPV and ground-mounted photovoltaic (GPV) systems installed side by side in an urban area under semiarid climate. The analysis considers operating weather conditions, and focuses on photovoltaic (PV) modules’ thermal and electrical behavior, as well as on the impact of FPV on the water evaporation rates. The FPV system covers 50% of the surface of a water tank; an adjacent uncovered tank is used as a reference for evaporation data. Overall, FPV and GPV modules show a similar electrical performance, with equivalence tests indicating that differences remain practically negligible at the operational scale (between $-$1.08% and 0.06%). FPV modules often operate at similar or slightly higher temperatures than GPV modules, consequence of low wind speed values, usually found in urban environments. In contrast, FPV modules consistently reduce water evaporation, with an average reduction of 40%, saving about 8.4 m$^{3}$ during the period.
The accelerated increase in demand for III-V space photovoltaics on GaAs and Ge substrates, as well as growing interests in terrestrial applications, motivate the development of cost-effective, high-throughput processing routes of these materials. Here, we assess spray-coated silver (Ag) back contact metallization as a substitute for electron-beam-evaporated metals currently used in industry. We find that the spray-coated Ag films are dense and continuous. By means of quantum efficiency, dark current-voltage, and illuminated current-voltage characterizations, we show that spray-coated GaAs and Ge solar cells perform similarly to baseline devices with electroplated Au, including under high current densities. We estimate that the thresholds for specific contact resistance below which back contacts do not significantly contribute to resistive loss are 2.1 x 10(-1) Omega center dot cm(2) for GaAs and 4.7 x 10(-2) Omega center dot cm(2) for Ge. We experimentally confirm that our spray-coated samples meet these requirements. Peel tests show that the adhesion of plain spray-coated Ag films to the back of p-type Ge substrates used in III-V solar cells is currently insufficient, whereas adhesion to p-type GaAs substrates is outstanding and requires no further optimization.
This article presents a robust and realistic evaluation of bifacial photovoltaic models. The approach mirrors standard characterization practice, enabling assessment not only of the intrinsic model accuracy but also its practical expandability under real operating conditions. The evaluation extends beyond conventional bifacial analysis and explicitly addresses rear-only performance, often neglected in the literature. The models examined are as follows: first, standard single-diode model (SDM), second, parallel-SDM, third, photocurrent-SDM, fourth, SeriesRes-SDM, and fifth, DiodeRes-SDM. Experimental measurements using Renogy RSP220DT-G1 module were conducted under different meteorological conditions, tilt angles, and surface albedo for validation. The results indicate that the DiodeRes-SDM achieves the highest bifacial accuracy [mean absolute error (MAE): 4.89%], while the SeriesRes-SDM is a comparable, simpler alternative (5.48%). Photocurrent-SDM and Parallel-SDM are most accurate for rear-only operation but perform poorly in bifacial mode. The Standard-SDM, while the simplest, introduces higher errors (7.92%). The evaluation confirms that rear operation exhibits distinct dynamics that require the development of rear-specific models. Therefore, choosing the appropriate bifacial model based on the specific application, bifacial yield prediction, system design, or installation condition optimization, is crucial for optimizing both modeling accuracy and computational efficiency.
We investigate the degradation of n- and p-type tunnel oxide passivating contact (TOPCon) under illumination and elevated temperatures to elucidate the degradation mechanism and identify mitigation strategies. Because the understanding regarding surface-related degradation (SRD) differs between n- and p-type TOPCon, we address different aspects for each layer type. Regarding p-type TOPCon, the focus is on the impact of the fast-firing peak temperature, whose correlation has already been investigated for n-type TOPCon but not for p-type TOPCon. It is found that the degradation extent of p-type TOPCon is inversely correlated with the peak temperature of the fast-firing step. This is consistent with previous reports on n-type TOPCon, making a common degradation mechanism for n- and p-type TOPCon likely. For n-type TOPCon, samples processed by plasma-enhanced chemical vapor deposition and low-pressure chemical vapor deposition (LPCVD) exhibit markedly different degradation extents. We attribute the lower degradation extent observed for LPCVD layers to its higher phosphorus concentration. We propose a unified mechanism for the degradation of both, n- and p-type TOPCon, that explains the various experimental data: hydrogen diffuses from a hydrogen containing dielectric layer (e.g., silicon nitride, SiNx) through the highly doped poly-Si layer toward the Si/SiO2 interface, where interface defects are formed. Based on this pathway, the degradation can be mitigated either by reducing the hydrogen content within the dielectric layers or by hindering the diffusion of hydrogen to the Si/SiOx interface—for example, by increasing the poly-Si dopant concentration.
When developing systems for perovskite solar cells (PSCs), it is important to have a testing platform that closely resembles your deployed systems. While developing a 1 U CubeSat, the Big Red Sat-1 at the University of Nebraska-Lincoln, we found a lack of passive curve tracing instrumentation, which we needed for our mission. To that end, we developed a benchtop passive curve tracer that leverages the Ossila Solar Simulator as an AM1.5 light source. This device utilizes a ladder of switched resistors and a precision voltage and current measurement to achieve the curve tracing. It also integrates a common-anode multiplexer to switch through multipixel PSCs. Finally, the solar cell holder is separate from the main measurement system, so various substrates sizes and pixel counts can be supported. This system is tested using various PSCs. It has been open sourced to enable reuse in future systems that may benefit from the lower power consumption and flight heritage.
Colloidal PbS quantum dots synthesized by a one-step direct-synthesis technique show great potential to develop low-cost and scalable manufacturing of quantum dot solar cells. However, the hole-extracting layer is still a barrier to the direction of scalability and performance of devices. Therefore, we successfully introduced a thin bulk heterojunction of PTB7-Th and fullerene (PC71BM) into the direct-synthesis-based PbS quantum dots solar cells. PTB7-Th:PC71BM-based device efficiently enhances light harvesting efficiency as well as acts as an interfacial charge transfer layer. It delivers a power conversion efficiency of 8.63%, which is higher than that of devices based on PTB7-Th (6.98%) and pristine colloidal PbS (0.94%) only. The increase in power conversion efficiency is due to the increased values of short-circuit current, open-circuit voltage, and fill factor for the solar cells after the incorporation of the PTB7-Th:PC71BM layer. More importantly, this work will inspire the exploration of various donor and acceptor combinations as an interfacial charge transfer layer to construct low-cost, scalable, and high-efficiency solution-processed organic-inorganic colloidal quantum dots solution-processed optoelectronic devices.
Among emerging materials, perovskite solar cells (PSCs) have attracted significant interest due to their high efficiency in laboratory settings. However, their performance under real outdoor environments remains insufficiently explored, largely because of the limited availability of perovskite module technology and the bulky, complex, and costly nature of conventional characterization equipment. This study presents a compact, cost-effective I-V tracer designed for both indoor and outdoor PSCs characterization. The device offers accuracy comparable to laboratory instruments, enabling comprehensive performance evaluation. It extracts key parameters from I-V curves, including open-circuit voltage (V-OC), short-circuit current (I-SC), maximum power point voltage (V-MPP), maximum power point current (I-MPP), fill factor (FF), and the power conversion efficiency (PCE), supporting sweeps from V-OC to I-SC and vice versa. It accommodates V-OC up to 3 V and I-SC up to 60 mA. Additionally, the system integrates environmental sensors to monitor solar irradiance (G), cell temperature (T-PV), ambient temperature (T-A), and humidity (H-A), facilitating precise outdoor performance analysis. Experimental validation confirms its accuracy and reliability across various conditions, bridging the gap between laboratory testing and real-world PSCs assessment.
