Progress in Photovoltaics最新文献

Perovskite/silicon tandem photovoltaic cells promise higher energy conversion efficiencies than silicon single junctions for reasonable additional production cost. However, they are more complex, due to the increased number of layers and to the perovskite material features regarding kinetic, stability, and surface homogeneity. Although measuring each subcell independently from each other is still a challenge, this work introduces a novel quantified electroluminescence (EL) imaging method of the top-cell ohmic shunt, a major issue in perovskite stacks. Device modeling, validated by experiments, led to ohmic shunt 2D resolution from differential EL measurements around 0.7 V, without optical filtering or spectral resolution. The shunt resistance maps of more than 60 cells were characterized, and the shunt quantification from these maps was consistent with electrical measurements. These maps provide relevant clues regarding ohmic defect origin by showing their strength, shape, and location. Applications range from lab-scale performance improvement and aging monitoring to manufacturing control including encapsulation.

Potential-induced degradation (PID) is a severe degradation mechanism in crystalline silicon (c-Si) photovoltaic (PV) modules. In p-type c-Si PV modules, PID results in the formation of shunt paths on the front side of negatively biased cells relative to the grounded frame due to the diffusion of sodium ions (Na⁺), a phenomenon known as PID shunting (PID-s). Various methods for PID-s recovery, which involve the outward diffusion of Na⁺, have been reported. However, whereas some cells show almost complete recovery, others exhibit no recovery at all. Conducting PID-s recovery without knowing the recoverability of the cells is inefficient and wasteful; therefore, a method to identify recoverable and non-recoverable cells prior to recovery is needed. In this work, a method using current-resolved electroluminescence (EL) imaging is proposed to identify recoverable and non-recoverable cells in a PV module by evaluating their PID-s nature as ohmic or non-ohmic, which depends on the concentration of Na⁺ ions. A total of 90 cells from three different modules are subjected to PID-s degradation and recovery. The experimental results show varying degrees of PID-s loss and recovery among the tested cells. The analysis highlights that non-ohmic shunts exhibit greater recovery potential than ohmic ones, a finding further verified using dark lock-in thermography (DLIT). Furthermore, the proposed method qualitatively provides insights into the recovery potential of individual cells, establishing EL imaging as an effective tool for assessing PID-s severity and predicting recovery. This paves the way for future advancements in PID-s diagnostics and mitigation strategies within PV systems.

Organometallic halide perovskites have received significant attention due to their promising optoelectronic properties, particularly in photovoltaics. The formation process of perovskite films is crucial in determining their structural and functional characteristics. In this study, the effects of methylamine vapour treatment and vacuum annealing on enhancing the crystallinity, morphology and structural integrity of perovskite films are examined. Methylammonium lead iodide (MAPI)–based perovskite films are investigated, with a focus on their crystallographic structure, vibrational modes and their correlation with device performance. Power conversion efficiencies (PCEs) of 19.5% and 18.6% have been achieved using one-step and two-step processes, respectively. The influence of trap states, film homogeneity and interfacial properties has been analysed through capacitance, photoluminescence and electroluminescence measurements, with recombination behaviour linked to crystallographic properties. These findings provide valuable insights into the role of processing techniques in the rejuvenation of perovskite solar cells. Additionally, they offer guidance for optimising fabrication strategies to improve film quality, device performance, stability and long-term reliability.

The market uptake of silicon heterojunction (SHJ) solar modules is projected to increase rapidly, which is expected to play a significant role in future sustainability. However, a major barrier to the mass production of SHJ solar modules is significant power degradation under ultraviolet (UV) irradiation. Here, we reported a 98.13% high-quantum yield and highly reliable CaSrSiO₄:Ce³⁺ UV-to-blue–violet downshifting (UV-DS) inorganic phosphor for photovoltaic applications, which could minimize UV-induced degradation, the levelized cost of energy, and the generation of photovoltaic module waste. The CaSrSiO₄:Ce³⁺ inorganic phosphor was synthesized via a solid-state reaction method, where Ce³⁺ ions preferentially occupy the 7-coordinated Ca site. As a proof of concept, an outstanding output power of 776.2 W and a module efficiency of 24.99% were achieved on 3.1 m² industrial-scale module. Only 2.49% power degradation was observed after 180 kWh/m² UV irradiation. A statistical lifetime assessment based on UV irradiance data of Chinese geographical locations proven that UV-DS encapsulants significantly enhanced the long-term stability of modules, with better power generation performance and economic and environmental characteristics. Our study offered a blueprint for designing SHJ photovoltaic modules sustainably and strategically for targeting geographic markets, mitigating one of the environmental risks associated with SHJ modules and accelerating practical application.

This work aims to define the optimization criteria for Cu(In,Ga)Se₂ (CIGS) as a bottom cell in a tandem structure, and to emphasize the differences from optimizing the CIGS when operating alone. Reproducing the single-cell recipes and only lowering the band gap is insufficient to optimize the bottom cell. We identified that the lack of high-energy photons, which are absorbed by the top cell, can cause a severe fill factor (FF) loss, and thus diminish the photovoltaic performance. With nonoptimized buffer layers (CdS and ZnMgO), S-shaped current-density-voltage (JV) characteristics leading to a low FF and poor performance can be observed. The S shape can be eliminated within seconds of white-light exposure and does not return for hours. Therefore, this does not pose a significant problem for single-cell operation. In the bottom-cell application, as only the low-energy part of the spectrum is available, the properties of the buffer layer(s) become crucial and additional optimization is necessary. Filtered JV measurements after white-light exposure could lead to overseeing important optimization steps. We discuss the causes for an S-shaped curve under filtered illumination, pinpoint the bottlenecks in the bottom-cell performance, and present a way to mitigate the losses.

Accelerated aging was used to assess environmental degradation in emerging co-extruded polypropylene (PP)-based backsheets under three different environmental conditions (65°C/20% relative humidity (RH), 75°C/20% RH, and 75°C/50% RH). Although differential scanning calorimetry did not measure crystallinity changes with exposure, spatially resolved Raman spectroscopy identified crystallinity increases in the core layer of aged samples, indicating a heterogeneous postcrystallization process. The Raman results were in agreement with synchrotron-based microfocused wide-angle X-ray scattering measurements. Cross-sectional nanoindentation was used to correlate localized crystallinity shifts with changes in Young's modulus. A similar trend was found where increased modulus was measured in the core layer, supporting the relationship between modulus and crystallinity. Finally, dielectric characterization was used to assess the impact of these material property changes on performance. While changes in the backsheet material properties and dielectric performance were observed with accelerated aging, these shifts generally equilibrated with time, indicating overall stability in response to environmental stressors. Additionally, the identified heterogeneous material property changes indicate that spatially resolved crystallinity measurements may be a valuable early failure indicator to be used in the assessment of PV backsheet long-term durability.

This study initially employs Cs₀.₀₅FA₀.₈₁MA₀.₁₄PbI₂.₈₆Cl₀.₁₄ as the active layer for perovskite solar cells and explores the impact of using different concentrations of natural Centella asiatica (CICA) extracts mixed with chlorobenzene (CB) as anti-solvent in the one-step method of perovskite film preparation. Centella asiatica is rich in natural antioxidants and asiatic acid. It contains many hydroxyl ions, which are capable of capturing uncoordinated heavy metal Pb atoms. We found that devices made with 15% Centella asiatica extract mixed with CB achieved the highest power conversion efficiency (PCE), increasing from 14.3% to 18.5%. Moreover, the devices maintained 85% of their initial efficiency after being stored in a glove box for 25 days.