Progress in Photovoltaics最新文献

Our previous work highlighted how microscopic structural effects influence the sheet and contact resistance of electrically conductive adhesives (ECAs). Herein, we delve further by investigating how the contact and bulk resistivity of several ECAs that are based on the same formulation, but with different filler content, are correlated with the filler content. Additionally, two different filler geometries — high and low surface area (HSA and LSA) fillers — are combined in different ratios to maintain a similar viscosity and therefore processability. Hence, contact and bulk resistivities are also correlated with the different geometry ratios of these two fillers. As expected, it was found that the contact and bulk resistivities decreased when the filler content was increased. However, the magnitude of the decrease was found to depend strongly on the filler geometry ratio. At extreme filler geometry ratios, when the bulk is either mostly loaded with HSA-fillers or mostly with LSA-fillers, the impact of changes in the filler content on the bulk and contact resistivities is markedly different. The measured data is interpreted within the context of percolation theory and it is determined that the optimum ratio of the LSA and HSA Ag-fillers investigated in this study is approximately 60:40 (for an epoxy-based adhesive). This work has important ramifications for the design of ECAs, where cost considerations and the need to reduce silver resource usage demand the lowest (silver) filler content, but the demands of product performance point to higher filler content.

Perovskite-silicon (Pero-Si) tandem solar cells have made remarkable progress in recent years, achieving certified cell efficiencies of up to 33.9%. However, accurately measuring the efficiency and current density-voltage (JV) curves of these devices poses various challenges including the presence of mobile ions within the perovskite absorber that lead to short- and long-term transient effects. Consequently, both the measurement setup and the preconditioning of the device significantly affect measurement results. This study focuses on enhancing the reliability and comparability of JV and other efficiency measurements for Pero-Si tandem devices through a systematic analysis of the influence of mobile ions, preconditioning and measurement conditions. For the first time, a full opto-electrical simulation model for Pero-Si tandem devices is presented in Sentaurus TCAD, which includes the drift-diffusion of anions and cations and is therefore able to describe short- and long-term transient device effects in state-of-the-art Pero-Si tandem cells. Experimental validation and evidence are given by comparison to in-house Pero-Si tandem cells, as well as Pero-Si mini modules from Oxford PV. We analyze by simulation and experiment how the cell preconditioning at different preconditioning voltages and times impacts the resulting measured tandem efficiency, as well as impact of JV scan times for the measured hysteresis in Pero-Si tandem devices. Furthermore, we demonstrate the impact of current-mismatching conditions on the measured hysteresis of the Pero-Si tandem device and the need of correct spectral irradiance settings during measurements. We showcase that even a very slight variation in short-circuit current density (j_sc) around the current-matching point leads to significantly different hysteresis behaviors. With aid of our simulation model, we could attribute this phenomenon to a reverse/forward biasing of the perovskite sub-cell impacting the ion drift depending on the current-limiting sub-cell of the tandem device. Therefore, it is sensible to be aware of the current limiting sub-cell for the comparison of the hysteresis susceptibility of different Pero-Si tandem devices. This study strongly underscores the importance of including the preconditioning and measurement conditions when reporting Pero-Si tandem efficiencies. The findings highlight the urgent need for standardization in the field.

We modeled the photovoltaic conversion of all-perovskite (PVK) double- and triple-junction solar modules to clarify the configurations suitable for the monolithically series-interconnected structure, which offers high scalability by fully exploiting the advantages of the thin-film modules over wafer-based crystalline-silicon modules. We first formulated the photovoltaic processes of single cells and modules by reference to previously reported data, next optimized the module structure parameters including the bandgaps of PVKs, cell widths, and transparent-electrode thicknesses, and then evaluated the annually averaged conversion efficiencies (η_annual) defined by the ratio of the annual energy yield to the annual insolation in outdoor environments using a meteorological database. The double-junction four-terminal (2J-4T) module overcomes the shortcomings involved in the two-terminal module consisting of series-connected top and bottom cells, providing higher η_annual and more options of the top-cell bandgap; the latter allows us to select a more durable PVK composition. However, the dual output (four terminals) is practically a serious drawback. The double-junction voltage-matched (2J-VM) configuration eliminates this drawback, that is, realizes the single output (two terminals) with taking over the advantages of 2J-4T, and hence, 2J-VM would be the most promising candidate. However, when the VM configuration is applied to the triple-junction modules, the ohmic loss and optical loss in the transparent electrodes used for the three submodules are more detrimental. To mitigate this shortcoming, we proposed a new configuration of the triple-junction series/parallel-connecting voltage-matched (3J-SPVM) module. This uses only two substrates with securing high η_annual and other advantages of the VM configuration, which contributes to cost reduction. Consequently, 3J-SPVM is potentially the most promising configuration for widespread use.

Currently, the Si solar cell market share is dominated by PERC solar cells. Although the efficiency of PERC solar cells has been steadily increasing, it is expected to reach the practical efficiency limit in the near future. The thin film/PERC Si tandem cell technique can be one of the solutions to overcome the single-cell efficiency limit. In this study, we developed a novel interlayer fabrication technology for the diffused junction Si solar cells of the PERC and Al BSF cell architectures. We combined laser contact opening (LCO) and laser-induced forward transfer (LIFT) processes to fabricate local contact opening with low contact resistance while maintaining the high passivation performance of the Si bottom cell. The dielectric-passivated emitter of the Si solar cell was ablated locally by the LCO process, and subsequently, the Ti nanoparticles were transferred selectively by the LIFT process to the opened emitter region followed by transparent conducting oxide deposition. Laser process parameters were carefully optimized to fabricate low-loss interlayers. We applied the developed interlayer fabrication technology to the Si bottom cells of Al BSF and PERC cells. Finally, we demonstrated successfully the perovskite/PERC Si tandem cell with an interlayer developed in this study. The developed interlayer fabrication technology does not include a photolithography step and vacuum deposition processes for buffer metals; thus, we expect it may be more compatible with the mass production of thin film/diffused junction Si tandem solar cells.

The development of a transient temperature model of photovoltaic (PV) modules is presented in this paper. Currently, there are a few steady-state temperature models targeted at assessing and predicting the PV module temperature. One of the most commonly used models is the Faiman thermal model. This model is derived from the modified Hottel-Whillier-Bliss (HWB) model for flat-plate solar-thermal collector under steady-state conditions and assumes low or no thermal mass in the modules (i.e., short time constants such that transients are neglected, and steady-state conditions are assumed). The transient extension of the Faiman model we present in this paper introduces a thermal mass, which provides two advantages. First of all, it improves the temperature prediction under dynamic conditions. Second, our transient extension to the Faiman model allows the accurate parametrization of the Faiman model under dynamic conditions. We present our model and parametrization method. Furthermore, we applied the model and parametrization method to a 1-year data set with 5-min resolved outdoor module measurements. We demonstrate a significant improvement in temperature prediction for the transient model, especially under dynamic conditions.

As photovoltaic (PV) modules are exposed to high temperatures and humidity over time, they generate leakage current, which leads to potential-induced degradation (PID) and lower power output. In silicon, Cu(In,Ga)(Se,S)₂ (CIGS) thin film and perovskite solar cells, PID has been shown to be driven by the presence of Na in the module glass. PID stability is crucial for the commercialization of such solar modules. This study aims to confirm the leaching phenomenon of Na in soda–lime module glass and study the use of polytetrafluoroethylene (PTFE) as a moisture barrier to prevent PID. By water immersion and exposure to different temperature and humidity conditions, we exhibited Na leaching in soda–lime glass. Moreover, we demonstrate the use of an anti-PID moisture barrier made of PTFE, which was deposited using kinetic spraying between the cover glass and encapsulant in the solar module. The thickness of the moisture barrier was controlled by adjusting the deposition rate, and the PID characteristics were evaluated by manufacturing solar modules for different barrier thicknesses. Light current–voltage (LIV), dark current–voltage (DIV), and electroluminescence (EL) measurements confirmed that the PTFE moisture barrier effectively inhibits the degradation of solar cells. This study provides further insights into the Na leaching phenomenon and PID mechanism in PV modules and contributes to the design and development of more stable solar cells.

Solar simulators based on light-emitting diodes (LEDs) usually consist of many spectrally different LEDs, which in sum produce a sun-like spectrum. On the one hand, this results in the advantage of a high spectral tunability of these systems and on the other hand, however, also in the challenge of a high number of parameters which have to be set for the adjustment of a suitable simulator spectrum. Multijunction solar cells consisting of series-connected subcells are very sensitive to spectral irradiance conditions, which are affecting the current and the fill factor of the device. A precise adjustment of the simulator spectrum based on the spectral responsivity of the subcells is therefore essential for accurate multijunction measurements. Therefore, the number of spectrally different light sources used should be at least as high as the number of subcells in the device under test. However, for the measurement of multijunction devices, the much higher number of spectrally different light sources in common LED solar simulators results in a plethora of different simulator spectra, potentially suitable for the measurement. Furthermore, the nonlinear intensity characteristics of the utilized LEDs as well as the distance-dependent illumination uniformity of such solar simulators add complexity when aiming for a precise spectral adjustment. To tackle these challenges, a new spectral adjustment procedure which is based on a least square's solution algorithm and the definition of appropriate boundary conditions for the calculation of suitable simulator settings is introduced in this publication. Focusing on measurements carried out under constant illumination makes the presented method especially applicable for perovskite-on-silicon multijunction devices. Therefore, an adapted method for the determination of the solar simulator's spectral properties, considering thermal influences which are particularly relevant when carrying out continuous illumination measurements, is introduced in this work. The presented method is verified applying it on a Wavelabs SINUS 220 LED solar simulator by performing a measurement comparison on a multijunction solar cell with Fraunhofer ISE CalLab's well-established multilight source solar simulator.

Photovoltaic (PV)-powered vehicle applications are very attractive for reducing CO₂ emission and creation of new market. Development of Si tandem solar cells is very promising for high-efficiency and low-cost solar cells. This paper presents our approaches for III–V/Si 3-junction tandem solar cells. In this paper, 24.9% efficiency Si heterojunction solar cells and mechanically stacked four-terminal 35.8% InGaP/GaAs/Si three-junction tandem solar cell are shown. Roadmap for realizing high-efficacy three-junction tandem solar cells of more than 40% is discussed in this paper. Because efficiencies of record cell of 36.1% with III–V/Si three-junction tandem cells and 33.9% with perovskite/Si two-junction cells are lower compared to 39.5% with III–V three-junction solar cells, it is necessary to clarify and reduce several losses of Si tandem solar cells. This paper presents high efficiency potential of III–V/Si three-junction and perovskite/Si two-junction solar cells analyzed by using our analytical procedure and discusses about non-radiative recombination, optical, and resistance losses in those Si tandem cells. Current status of various solar cell module efficiencies including our new record efficiency Si tandem solar cell module with an efficiency of 33.66% is also analyzed.

Potential-induced degradation-polarization (PID-p) can reduce module power, but how to project the extent to which PID-p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full-size crystalline silicon PV modules for PID-p to provide field-representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID-p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID-p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real-world susceptibility to PID-p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m⁻² nm⁻¹ at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID-p with in situ dark current–voltage (I-V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m² exposure at 25°C using a flash tester.