Perovskite Silicon Tandem Solar Cells Research Articles

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.

Molecular engineering of hole-selective layer for high band gap perovskites for highly efficient and stable perovskite-silicon tandem solar cells

Molecular engineering of hole-selective layer for high band gap perovskites for highly efficient and stable perovskite-silicon tandem solar cells

Overcoming Two Key Challenges in Monolithic Perovskite‐Silicon Tandem Solar Cell Development: Wide Bandgap and Textured Substrate—A Comprehensive Review

Abstract33.7% of power conversion efficiency (PCE) in monolithic perovskite‐silicon tandem solar cells (PSTSCs) is an eye‐catcher. Still, the issues emerging from their two main requirements, wide band gap (WBG) perovskites and textured substrates, trigger phase segregation, voltage deficit, perovskite strain, high recombination rates, shunt paths, etc. In addition, the ill‐defined relations of most of these issues to the WBG perovskites and silicon texture originating from the conflicting research outcomes have become severe impediments to developing PSTSCs. From this perspective, an overview of the recently developed monolithic PSTSCs discussing the major hurdles in their up‐scaling, stabilities, and commercialization is presented.

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.

Interface engineering for high-performance, triple-halide perovskite-silicon tandem solar cells.

Improved stability and efficiency of two-terminal monolithic perovskite-silicon tandem solar cells will require reductions in recombination losses. By combining a triple-halide perovskite (1.68 electron volt bandgap) with a piperazinium iodide interfacial modification, we improved the band alignment, reduced nonradiative recombination losses, and enhanced charge extraction at the electron-selective contact. Solar cells showed open-circuit voltages of up to 1.28 volts in p-i-n single junctions and 2.00 volts in perovskite-silicon tandem solar cells. The tandem cells achieve certified power conversion efficiencies of up to 32.5%.

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

Optimization of Efficient Perovskite-Si Hybrid Tandem Solar Cells

Perovskite-silicon tandem solar cells have attracted much attention to photovoltaic community because of their high efficiency via easy fabrication methods and availability of precursor material abundant in nature. The properties of both perovskite and silicon meet ideal solar cell standards such as high light absorption potential, long carrier diffusion length and fast charge separation process. Semi-transparent solar cell with widely tunable band gap of perovskite material is compatible with silicon solar cell for tandem structures. A perovskite-silicon tandem solar cell four terminal configuration optimization was performed through numerical simulation. The optimized four terminal perovskite-silicon tandem solar cell performances was investigated by varying the thickness of top and bottom solar cell absorber layers, defect density of the absorber layer, and temperature. Perovskite-silicon tandem solar cell showed better photovoltaic performance under constant illumination condition. A high performance mechanically attached four terminal (4-T) perovskite-silicon tandem solar cell has total power conversion efficiency (PCE) of 34.88% by optimized parameters through simulation. It has shown 37% efficiency with matched current of 23.71mA/cm2. These numerical simulation results are provided the parameter values for further experimental assignment.

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

Structuring of perovskite-silicon tandem solar cells for reduced reflectance and thermalization losses.

Perovskite-silicon tandem solar cells have made rapid progress in the last decade. Still, they suffer from multiple loss channels, one of them being optical losses including reflection and thermalization. In this study, the effect of structures at the air-perovskite and perovskite-silicon interface of the tandem solar cell stack on these two loss channels are evaluated. Regarding reflectance, every structure evaluated led to a reduction relative to the optimized planar stack. The best combination of structures evaluated reduced the reflection loss from 3.1 mA/cm2 (planar reference) to 1.0 mA/cm2 equivalent current. Additionally, nanostructured interfaces can lead to a reduction in thermalization losses by enhancing the absorptance in the perovskite sub-cell close to the bandgap. This means that more current can be generated at a higher voltage under the assumption that current-matching is maintained and the perovskite bandgap is increased accordingly, pathing the way towards higher efficiencies. Here, the largest benefit was obtained using a structure at the upper interface. The best result yielded an increase of 4.9%rel in efficiency. A comparison to a tandem solar cell using a fully textured approach with random pyramids on silicon shows potential benefits for the suggested nanostructured approach regarding thermalization losses, while reflectance is reduced at a similar level. In addition, the applicability of the concept in the module context is shown.

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.

Indium-based transparent conductive oxides developed for perovskite and perovskite-silicon tandem solar cell applications

Silicon solar cells are a mature PV technology; however, they are approaching their fundamental efficiency limit. Further efficiency improvements require a technological change towards silicon-based tandem solar cells, where a second absorber material with a higher band gap is stacked on top of silicon to reduce thermalization losses. For this purpose, perovskite-based solar cells have gained growing interest due to their rapid improvements in power conversion efficiencies, and promises of lower levelized costs of electricity. However, for perovskite-silicon tandem solar cells to surpass the current industry standard of silicon solar cells, efficiencies higher than 30 %, and long-term device stability are required.This paper focuses on the goal of improving the overall device efficiency of perovskite-silicon tandem solar cells by optimization of the top transparent conductive oxide (TCO) electrode. Sputtering processes for the TCOs indium tin oxide (ITO) (standard DC sputtering with ceramic target) and indium zinc oxide (IZO) (reactive serial co-sputtering process - magnetron) were developed and investigated. TCO films were optimized with regard to their optical properties, quantified here as the absorption weighted with solar spectral data, as well as to their electrical characteristics assessed with 4-pt resistivity and Hall-effect measurements to quantify resistivity, carrier concentration, and mobility. The best performing TCOs were then integrated as front electrode in perovskite and perovskite-silicon tandem solar cells to evaluate their impact on the device level. The optimized IZO film resulted in up to 1 mA/cm2 improvement of short circuit current density of the tandem solar cells.

Halide Composition Engineered a Non-Toxic Perovskite–Silicon Tandem Solar Cell with 30.7% Conversion Efficiency

Since the conversion efficiency of silicon (Si)-based solar cells stagnates at 26.7% in the literature, extensive research and development activities are carried out on perovskite silicon-based tandem solar cells. However, the presence of lead (Pb) and the instability of perovskite prevent their large-scale implementation in the photovoltaic industry. Therefore, it is important to replace the hazardous material (Pb) in perovskite top cells to design non-toxic perovskite–silicon tandem solar cells. The current work yields much-needed studies to develop a non-toxic perovskite–silicon-based tandem solar cell. For the first time, methylammonium tin mixed halide (MASnI3–xBrx)-based materials are comprehensively investigated and optimized with respect to different halide compositions, absorber layer thickness, and bulk defect density in standalone configurations, followed by the development of a lead-free MASnI2Br1–Si-based tandem solar cell. The transfer matrix method and current matching techniques are used to design the two-terminal monolithic tandem cell, which showed a maximum conversion efficiency of 30.7% with an open circuit voltage (VOC) of 2.14 V. The results outlined in this manuscript will pave the way for the progress of highly efficient, non-toxic perovskite–silicon tandem solar cells.

Structural and Optical Properties of Vacuum‐Evaporated Mixed‐Halide Perovskite Layers on Nanotextured Black Silicon

To improve the absorption of light in two‐junction tandem perovskite–silicon solar cells, antireflective textures are often created on the front surface in the form of micronsized pyramids using wet‐chemical etching. It is known that single‐junction silicon solar cells with nanotextured black silicon (BS) formed by dry‐etching techniques are more efficient than pyramidal microtextures. Herein, experimental evidence of enhanced efficiency of structures using BS between the perovskite layer and the silicon substrate for the first time is demonstrated. BS is fabricated using plasma‐based reactive‐ion etching on the front surface of the crystalline silicon. The deposition of mixed‐halide perovskite layers is performed by vacuum coevaporation and sequential evaporation. The structural and optical properties of evaporated perovskite layers with various thicknesses are investigated. It is found that the structural‐phase quality (viz., surface coverage, chemical composition, dimensionality, crystallinity, and phase purity) of perovskite layers on planar and nanotextured substrates is similar. However, the root mean square roughness of the perovskite layers on nanotextured substrates is much higher, which reduces the reflection significantly, especially, in the range of radiation incidence angle up to 60°. These results pave the way for the development of high‐performance perovskite–silicon tandem solar cells for improved efficiency.

Stability challenges for the commercialization of perovskite–silicon tandem solar cells

Stability challenges for the commercialization of perovskite–silicon tandem solar cells

Nano-optical designs for high-efficiency monolithic perovskite–silicon tandem solar cells

Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.