Perovskite Silicon Research Articles

Subcell‐Resolved Electroluminescence Imaging of Monolithic Perovskite/Silicon Tandem Solar Cell for High‐Throughput Characterization

In the midterm future, the photovoltaic industry is expected to be dominated by two‐terminal (2T) perovskite–silicon (pero–Si) tandem solar cells, which have high energy conversion efficiency and require characterization for large‐scale production. Electroluminescence (EL) imaging is one of the most prevalent and nondestructive techniques for defect detection, recognition, and characterization in Si‐solar cells in mass production. This work presents an EL setup that enables fast, simultaneous, and separate luminescence capture from the two subcells of pero–Si tandem devices. To demonstrate the setup, several encapsulated 2T pero–Si tandem samples are investigated. First, the effect that resistive coupling between the two subcells has on defect appearance in EL images is recorded. Therefore, EL image under different operational conditions is recorded. A strong dependence of defect signatures on current injection is observed, that is explained partly by resistive coupling but partly as well by injection‐dependent changes of the prevalent defects in the cells. An investigation of preconditioning under dark forward operation reveals significant local decrease of EL intensity going along with rapid reversible or irreversible and severe degradation close to the edges of the samples. This degradation takes place under forward bias during a period of ≈1 h.

Energy Yield Modeling of Perovskite–Silicon Tandem Photovoltaics: Degradation and Total Lifetime Energy Yield

This study investigates the impact of degradation in perovskite‐silicon tandem solar cells by means of energy yield (EY) modelling over the entire lifetime. First, we assess the impact on EY of degradation in the individual solar cell parameters of the perovskite top cell. Our analysis reveals that degradation in fill factor, due to a decline in perovskite top cell shunt resistance (RSh), has the most severe impact on the EY, emphasizing the imperative to rectify perovskite imperfections in thin film processing causing RSh decline. Second, we investigate implications of degradation in the perovskite top cell on the EY of current mismatched tandem solar cells. Third, we examine critical thresholds for the “acceptable degradation levels” in the perovskite top cell with regard to degradation in each solar cell parameter, assuming that the total loss in EY must be comparable to the degradation in state‐of‐the‐art silicon. Overall, our study highlights that degradation of the perovskite top cell needs to be assessed with care when extrapolating the impact on the lifetime EY of perovskite‐silicon tandem solar cells. The severity of degradation for different degradation mechanisms in a single junction perovskite solar cell cannot be translated one‐to‐one to tandem devices.

Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells

Tailoring perovskite crystallization and interfacial passivation in efficient, fully textured perovskite silicon tandem solar cells

Edge passivation: Considerable improvement in photovoltaic performance of perovskite/silicon tandem solar cells

Edge recombination is considered hard to avoid entirely in silicon (Si) solar cells as well as Si-base solar devices, hindering their future commercialization. However, such an important issue in perovskite/silicon (PK/Si) tandem solar cells has not attracted much attention. Herein, a low-temperature, non-vacuum liquid-based edge passivation strategy (LEPS) to improve the power conversion efficiency (PCE) of PK/Si tandem solar cells is proposed. The minority carrier lifetime (τeff) of the PK/Si tandem sample with 495.8 μs significantly enhances to 739.7 μs after passivating the Si sub-cell edge recombination. The open circuit voltage (VOC) of the PK/Si tandem solar cell increases by up to +3.8%abs from the initial state after LEPS treatment due to edge passivation, leading to the PCE of the PK/Si tandem solar cell increases by up to +1.2%abs. Finally, a monolithic PK/Si tandem cell with a PCE of 29.48% was achieved by further utilizing the LEPS, which opened up a simple and effective avenue for enhancing the PCE of PK/Si tandem solar cells and further promoting a higher photovoltaic output power of tandem modules.

Latest Advancements in Solar Photovoltaic-Thermoelectric Conversion Technologies: Thermal Energy Storage Using Phase Change Materials, Machine Learning, and 4E Analyses

In recent times, the significance of renewable energy generation has increased and photovoltaic-thermoelectric (PV-TE) technologies have emerged as a promising solution. However, the incorporation of these technologies still faces difficulties in energy storage and optimization. This review paper addresses these challenges by providing a comprehensive overview of the latest advancements in PV-TE technologies. The paper emphasizes the integration of phase change materials (PCMs) for thermal energy storage, also buttressing the use of encapsulated PCM for thermal storage and efficiency, and the use of hybrid PCM to enhance overall performance. Furthermore, reviews on the use of machine learning techniques for efficient optimization and the integration of thermoelectric modules into tandem perovskite silicon solar cells have been comprehensively analyzed. The advancements in photovoltaic-thermoelectric systems, as reviewed in this article, signify significant progress in attaining sustainable and effective energy production and storage. This review comprehensively addresses the 4Es, underlining their importance. It not only consolidates recent developments but also charts a path for future research in the field of PV-TE technologies, offering precise insights to guide upcoming studies and innovations.

Scenario-based recycling strategies for perovskite-silicon tandem solar cells: a harmonized life cycle assessment study

Environmental performances of end-of-life strategies for perovskite–silicon tandem solar cells.

Toward efficient and industrially compatible fully textured perovskite silicon tandem solar cells: Controlled process parameters for reliable perovskite formation

AbstractCapitalizing 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.

Nanostructured anti-reflection coating for absorption enhancement in perovskite silicon tandem solar cells

Perovskite-silicon tandem solar cells have captured the attention of the solar cell research community due to the advantages of perovskites, such as, an easy fabrication process using sol-gel methods and silicon bottom cells that can be fabricated using well-established fabrication techniques. The present study discusses the design, optimization, and numerical analysis related to the role of nanostructured anti-reflection coating design for perovskite (MAPbI3) silicon tandem solar cells. In the design, the top cell is taken as MAPbI3 and the bottom cell is C-silicon. The anti-reflection coating is designed with SiO2 nanoparticles embedded in ITO. These nanostructured top anti-reflection coating results are compared with its planar top cell counterpart. SiO2 nanoparticle diameter and interparticle separation are optimized to get maximum absorption in the top cell. Upon optimization, it was found that a design having SiO2 nanoparticles with a diameter of 60 nm and no interparticle separation showed the most reduction in reflection, which in turn led to an increase in absorption in the top cell. The proposed structure enhances current density by 8.3% over the planar cell. This top cell current is matched to the bottom silicon thickness. These findings were validated using Mie scattering and the Bruggmann effective medium approximation.

Analysis of nanostructured anti reflection coating for various perovskite layer thicknesses in perovskite silicon tandem solar cells

The anti-reflection coating (ARC) plays an important role in the design of every kind of solar cell. The suitable optimization of the ARC layer can make a lot of difference in the final output of the cell, by reducing the reflections at the surface. In this regard, the present paper highlights and analyses numerically the effect of nanostructured ARC for different top perovskite layer thicknesses in perovskite-silicon tandem solar cells. In the present case, the nanostructures for ARC are considered to be made up of SiO2 nanoparticles (NP) embedded in ITO. To evaluate the effect of nanostructure for this proposed cell, the nanostructured tandem cell is compared with its planar ARC-based reference cell. The top perovskite active thickness is varied from 100 nm to 800 nm. It has been found that the effect of nanostructured ARC is more pronounced for thinner perovskite layer-based cells than for thicker layers. To reduce reflections at the front surface, the SiO2 NP diameter and inter-particle spacing are optimized. With the nanostructured ARC at the top, the cell achieved the current density rise of 11.3% as compared to the reference cell for a 100 nm thick perovskite-based tandem cell design. As both the sub-cells are in series in tandem design, the top cell current is matched to the bottom silicon layer current by optimizing the bottom cell too. The proposed ARC design has the added advantage that it can simply be done with sol–gel processes.

Versatile implied open‐circuit voltage imaging method and its application in monolithic tandem solar cells

AbstractAs the efficiency of perovskite silicon tandem solar cells is increasing, the upscaling for industrial production is coming into focus. Spatially resolved, quantitative, fast, and reliable contactless measurement techniques are demanded for quality assurance and to pinpoint the cause of performance losses in perovskite silicon tandem solar cells. In this publication, we present a measurement method based on spectrally integrated photoluminescence (PL) imaging to extract subcell‐selective implied open‐circuit ( ) images from monolithic perovskite silicon tandem solar cells. We validate the approach using spectrally resolved absolute PL measurements based on an integrating sphere for the perovskite top cell and PL‐calibrated carrier lifetime images for the silicon bottom cell. Additionally, measurements of solar cells with low contact losses are used to validate the new measurement technique. We find a good agreement of the images with the validating measurements with a maximum deviation of well below 1% compared to the validation measurements.

Loss Analysis of Fully‐Textured Perovskite Silicon Tandem Solar Cells: Characterization Methods and Simulation toward the Practical Efficiency Potential

Optimally enhancing the performance of perovskite silicon tandem solar cells comes with accurate identification of loss origins in the device in combination with optoelectrical device simulations assessing the respective efficiency gains to prioritize optimization pathways. Herein, various characterization methods, namely, spectrally resolved photoluminescence (PL), transient‐PL, PL‐based implied open‐circuit voltage (iVOC) imaging, spectrometric characterization, and Suns‐VOC measurements are combined to quantify current density–voltage (jV) photovoltaic metric losses of a fully‐textured perovskite silicon tandem solar cell (26.7% efficiency). The extracted device characteristic parameters are then used as a reference for the comprehensive optoelectrical Sentaurus simulation model which precisely reproduces the experimentally obtained optical and electrical solar cell characteristics, considering mobile ion dynamics. Subsequently, starting from the current device design, the authors alleviate one step at a time the loss constraints and show the impact of each loss channel on the efficiency, identifying the three major ones to be at the: 1) perovskite/C60 interface (−4.6%abs) , 2) the series resistance (−2.9%abs), and 3) light management (−2.1%abs), which limit the VOC, fill factor, and jSC of the device, respectively. Furthermore, it is demonstrated that a practical efficiency potential of 39.5% can be regarded as a practical limit for the presented tandem device architecture.

Low-temperature metallization & interconnection for silicon heterojunction and perovskite silicon tandem solar cells

In this work, we present results on various low-temperature approaches for the metallization and interconnection of high-efficiency solar cells as silicon heterojunction (SHJ) or perovskite silicon tandems. By using fine line screen printing for the cell metallization and Ag-free or -reduced interconnection technologies, we demonstrate the potential of these approaches both for SHJ and perovskite silicon tandem cells. Furthermore, low-temperature (LT, ∼200 °C) or ultra-low-temperature (ULT, ∼150 °C) processes are utilized for metallization and interconnection to treat these temperature-sensitive solar cells with a reduced energy consumption. We compare LT soldering of SHJ cells with Pb-free alloys to state-of-the-art soldering processes and interconnection with electrically conductive adhesives (ECAs). For successful module integration of perovskite silicon tandem solar cells, these findings provide the basis to build full-size tandem modules with different interconnection technologies.

Understanding Contact Nonuniformities at Interfaces in Perovskite Silicon Tandem Solar Cells Using Luminescence Imaging, Lock‐In Thermography, and 2D/3D Simulations

The top cell of a perovskite silicon tandem solar cell requires several material layers on each side of the perovskite absorber to efficiently extract electrons and holes, respectively. These layers must meet multiple requirements simultaneously, namely, low interface recombination, good charge carrier selectivity, low contact resistivity, and high optical transparency. Due to the complex architecture, characterization techniques are required in material and process optimization to identify loss mechanisms. Spatial resolution of the characterization is gaining importance along with the upscaling of the perovskite technology. Herein, electro‐ and photoluminescence (EL and PL) imaging is combined with illuminated lock‐in thermography (ILIT) for a comprehensive electro‐optical characterization of both subcells in perovskite silicon tandem devices with state‐of‐the‐art cell architecture. Thereby, the combination of the presented characterization methods together with numerical simulation models enables to carry out holistic investigations of device limitations. The strength of this approach is showcased by one particularly remarkable feature that is observed in the investigated tandem device, showing a low PL but high EL signal at local spots. Together with multidimensional optoelectrical device simulations, the measurements are explained and the root cause of this feature to originate from the perovskite/C60 interface is suggested.

Performance improvement mechanisms of perovskite solar cells by modification of NiO hole-selective contacts with self-assembled-monolayers

This study investigates effects of the modification of NiOx hole-selective contacts (HSCs) with self-assembled monolayers (SAMs), [2-(9H-carbazol-9-yl) ethyl]phosphonic acid (2PACz), on the characteristics of perovskite solar cells, used for perovskite–silicon tandem cells. After the NiOx layers were fabricated by RF sputtering, the 2PACz modification was performed by the spin-coating of a 2PACz solution and subsequent annealing at 100 °C for 10 min. The 2PACz-modified NiOx layer improved the solar cells' open-circuit voltage and short-circuit current density. Photoelectron yield spectroscopy measurements imply that the 2PACz monolayers increase the work function of the NiOx HSCs, thereby enhancing field-effect passivation at the perovskite–HSC interface. Density functional theory calculations and electron spin resonance measurements indicate that an increase in the work function results from a vacuum level shift due to the electric dipole moment of 2PACz molecules and formation of space-charge region at the NiOx–2PACz interface. The performance improvement is explained as a result of enhanced field-effect passivation caused by the vacuum level shift and thus the increase in the work function. These findings, which clarify SAM modification effects of HSCs on solar-cells’ performance, can contribute to the development of highly efficient and reliable perovskite–silicon tandem solar cells.

Insights into Perovskite Film Formation Using the Hybrid Evaporation/Spin-Coating Route: An In Situ XRD Study

The hybrid evaporation/spin-coating route has been widely used for fabrication of highly efficient fully textured perovskite silicon tandem solar cells and is a promising route for upscaling. Nevertheless, fundamental aspects of the fabrication process such as the kinetics of perovskite crystallization and the influence of the environmental conditions remain uncertain. In this work, we investigate the individual stages of tandem-relevant 1.66 eV bandgap perovskite formation and map the structural evolution from the precursor to the perovskite phase until the degradation phase. We find that the kinetics of these transitions can be tuned by varying the humidity or the temperature during the annealing treatment. Specifically, increasing the relative humidity up to 50% elevates the reaction rate and results in improved perovskite quality. This is directly reflected in the solar cell power conversion efficiency with a 3%abs increment on average. While high annealing temperatures are found to promote large grain size growth and enhanced crystallinity, we observe that above 150 °C the remnant PbI2 precursor compromises film quality. Furthermore, the perovskite formation kinetics is fitted using the Johnson–Mehl–Avrami–Kolmogorov model. The Avrami constant is found in the range 0.66–0.87, indicating a diffusion-controlled one-dimensional growth process with an associated activation energy of 54.49 kJ/mol. Using in situ XRD, this work gives insights on key process parameters to ensure reproducible synthesis of high-quality perovskite films.

Minimizing electro-optical losses of ITO layers for monolithic perovskite silicon tandem solar cells

Minimizing electro-optical losses of ITO layers for monolithic perovskite silicon tandem solar cells

A Review on Stability Challenges and Probable Solution of Perovskite–Silicon Tandem Solar Cells

A Review on Stability Challenges and Probable Solution of Perovskite–Silicon Tandem Solar Cells

Ameliorating Properties of Perovskite and Perovskite–Silicon Tandem Solar Cells via Mesoporous Antireflection Coating Model

AbstractIt is anticipated that perovskite solar cells (PSCs) will overtake other products in the market for next‐generation photovoltaics. The optical loss, however, continues to be a flaw that restricts the photocurrent (Jph) of PSCs. Mesoporous antireflection coatings (ARCs), both monolayer and multilayer, are designed using a combination of the finite element method and equivalent medium theory, and ARCs models are merged with PSCs. In the current work, mesoporous ARCs are made, the optical performance of the device is evaluated using optical modeling, and then the ARCs are integrated into solar cells. The simulation results show that the Jph of planar inverted PSCs can increase to 24.00 mA cm−2 when the front surface of PSCs adopts mesoporous ARC (via parameter optimization and sensible arrangement and combination). An increase of 0.98 mA cm−2 in Jph of PSCs is observed in comparison with flat ARC (23.02 mA cm−2). The strong light transmission and low reflection properties of the mesoporous ARCs are confirmed by the optimized solution. It is important to note that the first fusion of mesoporous and multilayer ARC offers a fresh approach to the development of perovskite and perovskite/silicon tandem solar cells with extremely high efficiency.

Recycling Silicon Bottom Cells from End-of-Life Perovskite–Silicon Tandem Solar Cells

Perovskite–silicon tandem cells have shown much higher efficiencies than single-junction cells, which promises further reduction of energy cost from photovoltaics. Due to the protection by perovskites, silicon subcells in perovskite–silicon tandem cells may last much longer than those in single-junction devices. Herein, we report recycling silicon bottom cells from end-of-life perovskite–silicon tandem solar cells, which further reduces their cost and enhances the sustainability. We demonstrate that silicon bottom cells can be recycled from end-of-life tandem cells by thermal delamination and chemical cleaning processes. The optoelectronic properties of silicon bottom cells were shown to be largely unchanged in the end-of-life tandem cells. The efficiencies of tandem cells refurbished from recycled silicon bottom cells are comparable to those fabricated from fresh cells.

Maximizing Current Density in Monolithic Perovskite Silicon Tandem Solar Cells

Perovskite silicon tandem solar cells can overcome the efficiency limit of silicon single‐junction solar cells. In two‐terminal perovskite silicon tandem solar cells, current matching of subcells is an important requirement. Herein, a current‐matched tandem solar cell using a planar front/ rear side‐textured silicon heterojunction bottom solar cell with a p–i–n perovskite top solar cell that yields a high certified short‐circuit current density of 19.6 mA cm−2 is reported. Measures taken to improve the device are guided by optical simulation and a derived optical roadmap toward maximized tandem current density. To realize current matching of the two subcells, variation of the perovskite bandgap from ≈1.68 to 1.64 eV and thickness is investigated. Spectrometric characterization, in which current–voltage curves of tandem devices are recorded at systematically varied spectral irradiance conditions, is applied to determine the current matching point. In addition, remaining device limitations such as nonradiative recombination at the perovskite's interfaces are analyzed. Replacing the hole transport layer PTAA by 2PACz results in an overall certified power conversion efficiency of up to 26.8%. Precise simulation based on the device structure is essential as it provides efficient paths toward improving the device efficiency.