Progress in Photovoltaics最新文献

An epitaxial lift-off process utilizing an internal push–pull stressor scheme for the release of thin-film multijunction solar cells is reported. The process involves a sidewall protection step to localize the etching to the sacrificial layer. The sidewall protection allows etching of the sacrificial layer utilizing typical hydrofluoric and hydrochloric acid solutions, while preventing etching of Al and P containing layers forming the active region of the III–V tandem stack. The proposed thin-film process was validated by releasing a ~ 8-μm thick GaInP/GaAs/GaInNAsSb triple-junction solar cell structure grown on a GaAs substrate. The integrity of the released solar cell structure was confirmed by focused ion beam scanning electron microscopy. The crystalline quality and strain relaxation in the thin-film after the i-ELO process was studied by reciprocal space mapping with x-ray diffractometry, revealing a high integrity of the released film. The presented approach is primarily targeted for the lift-off of relatively thick multijunction solar cell films, for example including three or more junctions, alleviating possible etchant-related restrictions for the choice of III–V materials forming the multijunction structure.

The finite difference time domain (FDTD) method has been used to model the optical properties of ZnO/Ag/ZnO (ZAZ) multilayer structure. We proposed two configurations: a 5- to 15-nm-thick ZnO dense layer (DL) and ZnO nanoparticle (NP) coatings in monolayer, bilayer, and trilayer around Ag nanowire (AgNW) with a 30-nm diameter. The configurations were designed to improve the ZAZ electrode performance in organic photovoltaics (OPVs). The plasmonic resonance behavior of ZnO coated AgNW was analyzed in air and later incorporated into a ZAZ electrode with PM6:Y6 (active layer), yielding excellent plasmonic results for both configurations. Our results further reveal that ZnO DL coatings offer superior field confinement, while ZnO NP coating shows promising light-scattering capabilities, particularly beneficial for maximizing energy transfer to the active layer in OPV devices. The experimental transmission spectra of ZAZ electrodes closely align with the theoretical model, confirming their accuracy. Integrating ZnO NP layers into ZAZ electrodes with strong plasmonic performance offers promising potential for enhancing light absorption in the photoactive layer and improved device efficiency.

Sinha, A, Qian, J, Moffitt, S L, Hurst, K, Terwilliger, K, Miller, D C, Schelhas, L T, and Hacke, P. UV-Induced Degradation of High-Efficiency Silicon PV Modules With Different Cell Architectures. Prog Photovolt Res Appl. 2023; 31(1): 36–51, https://doi.org/10.1002/pip.3606.

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Fast and accurate performance analysis of fielded solar modules is essential for the reliable, long-term operation of large-scale solar farms. Daylight photoluminescence imaging has emerged as a promising inspection method, providing quantitative information while circumventing many logistical constraints associated with alternative methods. Luminescence images of modules acquired with partial current extraction reveal series resistance defects, a key contributor to cell and module degradation. A novel method is presented to estimate the reduction in output power caused by series resistance defects, based purely on daylight photoluminescence image data. This automated process generates electrical models to match series resistance-related intensity variations observed in daylight photoluminescence images, which are used to quantify performance losses. Cell-level simulations and experimental results are presented, yielding excellent results, as well as promising proof-of-concept demonstrations on full modules.

A recent trend in commercial PV modules is a transition to n-type silicon cells, including passivated emitter rear totally diffused (n-PERT), tunnel oxide passivated contact (TOPCon), and silicon heterojunction (SHJ). There is evidence via lab studies that some of these cells are more susceptible to UV induced degradation (UVID), yet there is a lack of confirmation that such degradation occurs in the field. Current IEC standards designed to screen for early module failures require only minimal UV exposure (15 kWh/m² 280–400 nm, ~2–3 months equivalent outdoor exposure). Here, we investigate fielded n-PERT silicon (Si) modules from a commercial utility that show power losses of ~2%/year. We present a comprehensive picture of the physics and chemistry of degradation supported by both module and cell electronic characterization (EL, PL, IV, EQE, and DLIT) and materials-level morphological and chemical analysis (SEM, EDS, XPS, FTIR, and HPLC). All sampled site modules show short circuit current (I_sc) and open circuit voltage (V_oc) losses when compared to unfielded spares, with the most severely degraded also having losses in fill factor (FF). We identify two different degradation modes contributing to overall power loss: (1) external quantum efficiency (EQE) measurements show losses in the blue range of the spectra, indicative of cell surface recombination losses, and (2) variations in high series resistance (R_s) at the cell level that are correlated with compositional differences in cell metallization. Using unfielded spares, we were able to reproduce V_oc, I_sc, and EQE losses via a minimum UV stress of 67.5 kWh/m² (280–400 nm), 4.5× the exposure currently required in IEC 61215-2 (MQT 10). Degradation continued with additional UV dosage equivalent to the fielded modules (405 kWh/m² total), with power loss leveling out at an average of 6.1%. Subsequent 1000 h of 85% RH/85°C damp heat testing showed that cells exposed to UV underwent additional severe series resistance degradation, even those without the susceptible paste composition seen in the field, whereas non-UV exposed cells saw little change. We attribute this to higher concentrations of acetic acid generated on the UV exposed area of the module, leading to degradation of the gridline/cell interface and high R_s. This study is unique in that it reproduces field observed utility scale UVID with an accelerated test and supports the need for standards development for longer UV exposure combined with other stress factors to catch materials interplay within a module package.

This work investigates the influence of the metallization of low-temperature Cu paste and AgCu paste on the performance of SHJ solar cells through a comprehensive study of two techniques—screen printing (SP) and dispensing. The research successfully applied Cu and AgCu pastes as metal contacts on SHJ solar cells, yielding promising results. Notably, cells with AgCu paste SP on the front side and Ag paste SP on the rear side achieved a 0.13% efficiency gain over reference Ag SP bifacial cells. Moreover, cells with AgCu paste SP on the front side and Cu paste SP on the rear side reached an efficiency of 23.6%, just 0.35% lower than the reference cells, while saving approximately 70% of Ag paste. Cells with Cu paste SP on both sides recorded an average efficiency of 22.4% and a maximum of 23.08%, the highest efficiency reported for cells using Cu SP on both sides (zero Ag). Cells with Cu dispensing on the rear side also demonstrated superior performance compared to cells with Cu SP on the rear side. Along, we assessed the finger-printed characteristics of the three pastes and the performance of SHJ solar cells under various annealing conditions including the Cu annealing conditions (300°C for 5 s). The solar cells maintained stable performance up to 280°C for 5 s, with degradation observed above this temperature, and light soaking partially recovered some of the efficiency loss. A 0.2% drop persisted under Cu annealing conditions, but light soaking reversed this effect back to the original efficiency. This work advances SHJ solar cell technology by highlighting the potential of AgCu and Cu pastes to efficiently replace or reduce Ag paste consumption in SHJ solar cell metallization.