Progress in Photovoltaics最新文献

This paper provides a comprehensive assessment of the up-to-date life-cycle sustainability status of cadmium-telluride based photovoltaic (PV) systems. Current production modules (Series 6 and Series 7) are analyzed in terms of their energy performance and environmental footprint and compared with the older series 4 module production and current single-crystalline Silicon (sc-Si) module production. For fixed-tilt systems with Series 6 modules operating under average US irradiation of 1800 kWh/m²/year, the global warming potential (GWP) is reduced from 16 g CO_2eq/kWh in Series 4 systems to 10 CO_2eq/kWh in Series 6 systems. For operation in US-SW irradiation of 2300 kWh/m²/year, the GWP is reduced from 11 to 8 CO_2eq/kWh and for 1-axis tracking systems operating in Phoenix, Arizona, with point-of array irradiation of 3051 kWh/m²/year the GWP is reduced to 6.5 CO_2eq/kWh. Similar reductions have happened in all environmental indicators. Energy payback times (EPBT) of currently installed systems range from 0.6 years for fixed-tilt ground-mounted installations at average US irradiation at latitude tilt installations to 0.3 years for one-axis trackers at high US-SW irradiation, considering average fossil-fuel dominated electricity grids with fuel to electricity conversion efficiency of 0.3. The resulting energy return on energy investment (EROI) also depends on the conversion efficiency of the electricity grid and on the operation life expectance. For a 30-year operational life and grid conversion efficiency of 0.3, EROI ranges from 50 (at US average irradiation) to 70 for US-SW irradiation. The EROI declines with increased grid conversion efficiency; for CdTe PV operating in south California with grid conversion efficiency of 49%, the EROI is about 50 and is projected to fall to 30 when the state's 2030 target of 80% renewable energy penetration materializes. Material alternatives that show a potential of further reductions in degradation rates and materials for enhanced encapsulation that would enable longer operation lives have also been investigated. A degradation rate of 0.3%/year, which has been verified by accelerated testing, is assumed in 30-year scenarios; this is projected to be reduced to 0.2%/year in the near-term and potentially to 0.1%/year in the longer term. With such low degradation rates and enhanced edge-sealing, modules can last 40- to 50-years. Consequently, all impact indicators will be proportionally reduced while EROI will increase. This detailed LCA was conducted according to ISO standards and IEA PVPS Task 12 guidelines. The study revealed that the choices of system models, methods and temporal system boundaries can significantly impact the results and points out to the need to include assumptions regarding these choices in the “transparency in reporting” requirements listed in the IEA PVPS Task 12 Guidelines.

Concentrating photovoltaics is an attractive route for achieving high power output with thin film solar cells, using low-cost optics. In this work, the performance of CdTe:As thin film solar cells on two different transparent conducting oxide (TCO)-coated substrates is investigated and compared under varying concentrated light intensities (1–6.3 Suns). Samples tested had CdZnS/CdTe:As devices deposited atop of either a soda-lime glass with a fluorine-doped tin oxide TCO or an ultra-thin glass (UTG) with an aluminium zinc oxide TCO and ZnO high-resistive transparent (HRT) layer. Device current density was found to increase linearly with increased light intensities, for both sample configurations. Power conversion efficiencies of both device samples decreased with increased light intensity, due to a decrease in fill factor. The fill factor, for both sample configurations, was affected by reducing shunt resistance with increasing illumination intensity. The two device types performed differently at the high illumination intensities due to their series resistance. Light-soaking devices under 6.3 Suns illumination intensity for 90 min showed no significant performance degradation, indicative of relatively stable devices under the highest illumination intensity tested. Efficiency limiting factors are assessed, evaluated and discussed.

Multi-junction photonic power converters (PPCs) are photovoltaic cells used in photonic power transmission systems that convert monochromatic light to electricity at enhanced output voltages. The junctions of a multi-junction PPC have overlapping spectral responsivity, which poses a unique challenge for spectrally resolved external quantum efficiency (EQE) measurements. In this work, we present a novel EQE measurement technique based on a wavelength-tunable laser system and characterize the differential multi-junction device-level EQE (dEQE_MJ) as a function of the monochromatic irradiance over seven orders of magnitude. The irradiance-dependent measurements reveal three distinct irradiance regimes with different dEQE_MJ. For the experimentally studied 2-junction GaAs-based device, at medium irradiance with photocurrent densities between 0.3 and 90 mA/cm², dEQE_MJ is independent of irradiance and follows the expected EQE of the current-limiting subcell across all wavelengths. At higher irradiance, nonlinear device response is observed and attributed to luminescent coupling between the subcells. At lower irradiances, namely, in the range of conventional EQE measurement systems, nonlinear effects appear, which mimic luminescent coupling behavior but are instead attributed to finite shunt resistance artifacts that artificially inflate dEQE_MJ. The results demonstrate the importance of measuring the device-level dEQE_MJ in the relevant irradiance regime. We propose that device-level measurements in the finite shunt artifact regime at low monochromatic irradiance should be avoided.

The reliability of CIGS solar systems in agricultural environments was investigated using an accelerated aging test. Both complete cells and representative stacks of selected layers and interfaces were exposed to humidity and temperature variations for 9 to 14 days with and without ammonium sulfate (NH₄)₂SO₄, an aerosol pollutant representative of agricultural activities. The performance evolution of complete cells was evaluated by J-V curves and EQE measurements. After 9 days, the presence of (NH₄)₂SO₄ led to a performance loss of 58%, significantly higher than the 37% loss observed without pollutants. Using computer calculations based on the two-diode model, it was possible to de-correlate some interactions between J-V parameters. The results of modeling suggested that the pollutant caused optical losses and conductivity loss of electrical contacts, presumably by corrosion. Sheet resistance and Hall effect measurements on the representative stacks of layers confirmed that the conductivity loss of ZnO:Al (AZO) after 14 days of aging strongly impacted the cell performance, this phenomenon being even more severe in the presence of (NH₄)₂SO₄. The conductivity of Mo remained significantly less affected by aging both with and without pollutants. The NiAlNi contacts after aging with (NH₄)₂SO₄ became so resistive that measurement was impossible. Corroborating modeling and experimental results, the drop in J_sc was attributed to the loss of the interference fringes in the AZO rather than to the loss of optical transmittance. Finally, aging without pollutants mostly impacted V_oc and R_sh due to the formation of shunt paths.

We assess the accuracy of two steady-state temperature models, namely, Ross and Faiman, in the context of photovoltaics (PV) systems integrated in vehicles. Therefore, we present an analysis of irradiance and temperature data monitored on a PV system on top of a vehicle. Next, we have modeled PV cell temperatures in this PV system, representing onboard vehicle PV systems using the Ross and Faiman model. These models could predict temperatures with a coefficient of determination (R²) in the range of 0.61–0.88 for the Ross model and 0.63–0.93 for the Faiman model. It was observed that the Ross and Faiman model have high errors when instantaneous data are used but become more accurate when averaged to timesteps of greater than 1000–1500 s. The Faiman model's instantaneous response was independent of the variations in the weather conditions, especially wind speed, due to a lack of thermal capacitance term in the model. This study found that the power and energy yield calculations were minimally affected by the errors in temperature predictions. However, a transient model, which includes the thermal mass of the vehicle and PV modules, is necessary for an accurate instantaneous temperature prediction of PV modules in vehicle-integrated (VIPV) applications.

Levelized cost of electricity (LCOE) is a crucial metric for assessing the socio-economic cost-efficiency potential of various energy sources including solar photovoltaics. Nevertheless, accurate LCOE estimations for commercialized high-efficiency Si solar modules with passivated emitter and rear cell (PERC) and silicon heterojunction (SHJ) structures have been lacking. In this study, we present the first global LCOE estimates for a PERC module (20% cell efficiency) and a SHJ module (23% cell efficiency), which have been derived by (i) performing rigorous energy-yield calculations with full-spectral and temperature-dependent simulations that incorporate all essential meteorological effects and (ii) considering country-specific capital costs and discount rates. Moreover, to determine the universal global LCOE, the LCOEs for three distinct installation capacities (100 MW for a utility, 500 kW for a commercial, and 5 kW for a residential system) have been unified by selecting an appropriate system size at each location based on a population density. We find that the LCOEs of both PERC and SHJ systems are below 3 cents/kWh in 2020 US dollar in many areas of China, Saudi Arabia, the United States, Australia, Chile, and Botswana, where the conditions of a high energy yield, low population density, low capital cost, and low country-risk premium are satisfied simultaneously. In contrast, many European countries exhibit a moderate LCOE of 3~5 cents/kWh. Notably, Japan and Russia exhibit quite high LCOEs (6~10 cents/kWh) primarily due to significantly higher installation costs and moderate energy yields. Importantly, the global LCOEs of the PERC and SHJ modules are quite similar, with the SHJ module showing a slightly better cost performance in the regions near the equator due to its low temperature coefficient. Conversely, the PERC module demonstrates a cost advantage in the Northern Hemisphere due to a lower module cost.

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2024 are reviewed.

Solar electricity is set to play a pivotal role in future energy systems. In view of a market that may soon reach the terawatt (TW) scale, a careful assessment of the performance of photovoltaic (PV) systems becomes critical. Research on PV fault detection and diagnosis (FDD) focuses on the automated identification of faults within PV systems through production data, and long-term performance evaluations aim to determine the performance loss rate (PLR). However, these two approaches are often handled separately, resulting in a notable gap in the field of reliability. Within PV system faults, one can distinguish between permanent, irreversible effects (e.g. bypass diode breakage, delamination and cell cracks) and transient, reversible losses (e.g. shading, snow and soiling). Reversible faults can significantly impact (and bias) PLR estimates, leading to wrong judgements about system or component performance and misallocation of responsibilities in legal claims. In this work, the PLR is evaluated by applying a fault detection procedure that allows the filtering of shading, snow and downtime. Compared with standard filtering methods, the addition of an integrated FDD analysis within PLR pipelines offers a solution to avoid the influence of reversible effects, enabling the determination of what we call the intrinsic PLR (i-PLR). Applying this method to a fleet of PV systems in the built environment reveals four main PLR bias scenarios resulting from shading losses. For instance, a system with increasing shading over time exhibits a PLR of −1.7%/year, which is reduced to −0.3%/year when reversible losses are filtered out.

An aluminum oxide (AlO_x)/silicon nitride (SiN_y) dielectric stack was developed using an industrial plasma-enhanced chemical vapor deposition (PECVD) system with low-frequency (LF) plasma source for the surface passivation of undiffused textured p-type crystalline silicon. The median recombination current density is 4.3 fA cm⁻² as determined from photoconductance decay lifetime measurements and numerical device modeling. To the best of our knowledge, this is the first time to present a high-quality LF-PECVD AlO_x/SiN_y passivation stack on undiffused textured p-type crystalline silicon wafers, which are cleaned with industrial processes using HF, HCl, and O₃. The simulation agrees well with the measured effective carrier lifetime if the velocity parameters of 5.6 cm s⁻¹ for holes and 803 cm s⁻¹ for electrons are applied with a fixed negative charge density of −3 × 10¹² cm⁻². The process integration of developed AlO_x/SiN_y dielectric stack is successfully demonstrated by fabricating p-type back junction solar cells featuring a poly-Si-based passivating contact at the cell rear side. As the best cell efficiency, we achieve 24.2% with an open-circuit voltage of 725 mV on a M2-sized Ga-doped p-type Czochralski-grown Si wafer as independently confirmed by ISFH CalTeC.