Progress in Photovoltaics最新文献

A world record conversion efficiency of 26.81% has been achieved recently by LONGi team on a solar cell with industry-grade silicon wafer (274 cm², M6 size). An unparalleled high fill factor (FF) of up to 86.59% has also been certified in a separated device. The theoretical FF limit has been predicted to be 89.26%, while the practical FF is far below this limit for a prolonged interval due to the constraints of recombination (i.e., SRH recombination) and series resistance. The ideality factor (m) in the equivalent circuit of silicon solar cells is consistently ranging from 1 to 2 and rarely falls below 1, resulting in a relatively lower FF than 85%. Here, this work complements a systematic simulation study to demonstrate how to approach the FF limit in design of silicon solar cells. Firstly, a diode component with an ideality factor equal to 2/3 corresponding to Auger recombination is incorporated in the equivalent circuit for LONGi ultra-high FF solar cell; Secondly, an advanced equivalent circuit is put forward for comprehensive analysis of bulk recombination and surface recombination on the performance, in which specific ideality factors are directly correlated with various recombination mechanisms exhibiting explicit reverse saturation current density (J₀). Finally, we evaluate precisely the route for approaching theoretical FF in practical solar cell fabrication based on electrical design parameters using the developed model.

Multidimensional simulations for diverse solar cells often encounter distinctive configurations, even when employing the same simulation software. The complexity and inefficiency of this process are further exacerbated when employing different simulators. From our extensive decade-long experience in numerical simulations of diverse solar cells, we have identified ten common simulation steps intrinsic to typical electrical and optical simulations. Subsequently, we propose ten sets of variables that encompass all the relevant details required for these steps. To address the challenge of varying information requirements for each variable across different simulations, we assign a list, a versatile data type, to each variable. This approach, by design, enables concise, coherent, and flexible input, accommodating the unique demands of each simulation. However, to ensure unambiguous simulations, precise specifications for these variables are essential. Computer code has been successfully implemented to ensure adherence to specifications and expedite variable synchronization with Sentaurus, the de facto standard for device simulation. Within this framework, users are only tasked with editing variables in a plain text file, obviating the need for in-depth knowledge of Sentaurus. This streamlines the prerequisites for engaging in numerical simulation significantly. Through thoughtful design considerations, we preserve the simulation capacity while simultaneously enhancing productivity considerably. This open-source framework welcomes global collaboration within the photovoltaic community and has the potential to generate an extensive dataset for cost-effective artificial intelligence training.

We present a simple yet powerful analysis of Suns-photoluminescence quantum yield measurements that can be used to determine the surface saturation current densities of thin film semiconductors. We apply the method to state-of-the-art polycrystalline perovskite thin films of varying absorber thickness. We show that the non-radiative bimolecular recombination in these samples originates from the surfaces. To the best of our knowledge, this is the first study to demonstrate and quantify non-linear (bimolecular) surface recombination in perovskite thin films.

In this work, we present the fabrication and analysis of a wafer-bonded GaInP/GaInAsP//Si triple-junction solar cell with 36.1% conversion efficiency under AM1.5g spectral illumination. The new cell design presents an improvement over previous III-V//Si triple-junction cells by the implementation of a rear-heterojunction for the middle cell. Furthermore, an advanced metallodielectric rear-side grating was used for light trapping enhancement in the silicon bottom cell that increased the silicon subcell current by 1.4 mA/cm². The external radiative efficiency was quantified to be 1.5 times higher compared to a reference device with a GaInAsP homojunction middle cell. A luminescent coupling factor of 0.46 between the middle and bottom subcell was determined. The share of recombination in the space-charge region was experimentally shown to be insignificant as intended by the rear-heterojunction design. Overall, the open-circuit voltage of the middle cell increased by 61 mV compared to the previous generation. Given the established long-term stability of III-V and silicon-based solar cells, these results are promising steps towards the future employment of III-V/Si tandem solar cells.

Photovoltaic (PV) modules are subjected to environmental stressors (UV exposure, temperature, and humidity) that cause degradation within the encapsulant and its interfaces with adjacent glass and cell substrates. To save experimental time and to enable long-term assessment with intensive degradation only taking place after many years, the development of predictive models is indispensable. Previous works have modeled the delamination of the ethylene vinyl acetate (EVA) encapsulant/glass and encapsulant/cell interfaces under field aging conditions with fundamental photochemical degradation reactions that lead to molecular scission and loss of interfacial adhesion, characterized by the fracture resistance, G_c. However, these models were fundamentally limited in that the following aspects were not incorporated: (i) molecular crosslinking in the field, (ii) synergistic autocatalytic interactions of degradation mechanisms, (iii) connection between degraded encapsulant structure and its mechanical properties, and (iv) rigorous treatment of the plasticity contribution to G_c with finite element models. Here, we present a time-dependent multiscale model that addresses these limitations and is applicable to a wide range of encapsulants and interfaces. For the reference EVA encapsulant and its interfaces with the glass and cell, the presented model predicts an initial rise in G_c in the first 3 years of field aging from crosslinking, then a subsequent sharp decline from degradation mechanisms. We used nanoindentation to measure the changes in EVA mechanical properties over exposure time to tune the model parameters. The model predictions of G_c and mechanical properties match with experimental data and show an improvement compared to previous models. The model can even predict switches in failure interfaces, such as the observed EVA/cell to EVA/glass transition. We also conducted a sensitivity analysis study by varying the degradation and crosslinking kinetic parameters to demonstrate their effects on G_c. Model extensions to polyolefin elastomer- and silicone-encapsulants and their interfaces are also demonstrated.

Capitalizing on the existing silicon industry, fully textured perovskite-silicon tandem solar cells have a great potential to penetrate the electricity market. While the use of textured silicon with large pyramid size (> 1 μm) enhances the power conversion efficiency (PCE), it also presents process complications. To achieve high performance, meticulous control of deposition parameters on textured silicon is required. This study provides a guideline for the use of the hybrid evaporation/spin-coating route to form high-quality perovskite absorbers. Using various characterization techniques, we highlight intrinsic differences between perovskite growth on flat versus textured substrates. Furthermore, we provide pathways to ensure a high perovskite phase purity, reveal mitigation strategies to avoid the formation of undesired dendritic perovskite structures, give guidelines to ensure photostability, and discuss the “misleading” effect of residual PbI₂ on the perovskite photoluminescence response. A good understanding of the perovskite growth on textured silicon enables the fabrication of a tandem device with a PCE > 26% (without employing additives or surface treatments) and a good operational stability. The comprehensive guidelines in this study provide a better understanding of perovskite formation on textured silicon and can be transferred when upscaling the hybrid route perovskite deposition.

Each solar cell is characterized at the end-of-line using current-voltage ($�I�V$) measurements, except shingle cells, due to multiplied measurement efforts. Therefore, the respective host cell quality is adopted for all resulting shingles, which is sufficient for samples with laterally homogeneous quality. Yet, for heterogeneous defect distributions, this procedure leads to (i) loss of high-quality shingles due to defects on neighboring host cell parts, (ii) increased mismatch losses due to inaccurate binning, and (iii) lack of shingle-precise characterization. In spatially resolved host measurements, such as electroluminescence images, all shingles are visible along with their properties. Within a comprehensive experiment, 840 hosts and their resulting shingles are measured. Thereafter, a deep learning model has been designed and optimized which processes host images and determines $�I�V$ parameters like efficiency or fill factor, $�I�V$ curves, and binning classes for each shingle cell. The efficiency can be determined with an error of $�0�.�06� �{\text{\%}}_{\text{abs}}$ enabling a $�13� �{\text{\%}}_{\text{abs}}$ improvement in correct assignment of shingles to bin classes compared with industry standard. This results in lower mismatch losses and higher output power on module level as demonstrated within simulations. Also, $�I�V$ curves of defective and defect-free shingle cells can be derived with good agreement to actual shingle measurements.

Due to reduced rear-side ventilation, building-integrated photovoltaics (BIPV) are prone to higher operating temperatures, which may impact their long-term performance and reliability. However, often overlooked in the study of thermomechanical stress in PV modules are the intraday temperature variations, resulting from factors such as cloud movements and subsequent changes in irradiance. This work proposes a statistical analysis of cell and module temperature measurements in single-cell c-Si modules on a test bench in Neuchâtel, Switzerland. The goal is to study and compare various BIPV-relevant module topologies with a range of factors such as the insulation type, tilt angle, and glass thickness. The standard indicators such as the 98th percentile temperature and diurnal temperature variations are examined, as well as proposed new thermomechanical stress indicators based on temperature gradients and cell versus module temperature differences. Unexpectedly, results indicate that, considering the intraday temperature variations, close-roof module configurations (with small ventilation gaps) are potentially at a higher risk of suffering long-term thermomechanical fatigue than fully insulated modules, which are exposed to higher operating temperatures.

Potential-induced degradation (PID) may be a serious concern in photovoltaic (PV) modules and plants, particularly when approaching high system voltages (1500+ V). Here, we investigate PID occurring in bifacial rear-emitter silicon heterojunction (SHJ) solar cells encapsulated in a glass/glass (G/G) module configuration with ethylene vinyl acetate (EVA) as an encapsulant. PID testing was performed at 85°C in 85% relative humidity (RH), and the solar cells were subjected to −1 kV and +1 kV for up to 800 h. SHJ cells were found to degrade when subjected to −1 kV, and to a lesser extent when left unbiased in damp heat (DH) conditions, while the application of +1 kV prevented degradation. Although prone to PID after extended test durations, the SHJ mini-modules investigated in this study noticeably passed the industry standard (IEC 61215:2021) PID test of 96 h. The degradation was primarily characterized by losses in short-circuit current (I_SC) at the front side, followed by fill factor (FF) and open-circuit voltage (V_OC). A cross-sectional transmission electronic microscopy analysis of the laminates subjected to −1 kV highlighted a transport of sodium (Na) through the transparent conductive oxide (TCO), reaching the amorphous Si/TCO interface. The samples tested in DH conditions and with positive PID test conditions did not exhibit such a migration of Na. To account for these observations, we updated a previously proposed model describing the sensitivity of SHJ cells to water. In our degradation model, moisture in the module corrodes the glass, creating sodium hydroxide (NaOH) that then percolate through the EVA before reaching the SHJ cell. The application of a high negative bias amplifies the previous mechanism by increasing the availability of Na⁺ and also enhances the drift of Na⁺ through the EVA to the cell. Finally, we demonstrate that PID can be mitigated or suppressed at the module level by using a high-volume resistivity encapsulant with a low water vapor transmission rate (WVTR) or by encapsulating SHJ solar cells in a configuration impermeable to water (e.g., using an edge sealant).