Top Solar Cell Research Articles

Unveiling recombination in top cells: SCAPS-1D simulations for high-efficiency bifacial planar perovskite/silicon tandem solar cells

Bifacial two-terminal (2T) perovskite/silicon tandem solar cells (TSCs) can enhance the current matching by utilizing albedo, thereby achieving higher power generation densities (PGDs) compared to their monofacial counterparts. Nevertheless, the PGDs of recently fabricated bifacial TSCs lag considerably behind the theoretical limit, primarily attributed to recombination losses in the top perovskite solar cells (PSCs). Herein, we model a bifacial planar perovskite/silicon 2T TSC using SCAPS-1D and analyze how radiative, Shockley-Read-Hall (SRH), Auger, and interface recombination in the PSC constrain the PGD of the bifacial 2T TSC under current matching/pseudo-matching conditions. Our findings indicate that recombination influences the PGD in the following order: interface (ETL/PVSK) > SRH > radiative > Auger > interface (PVSK/HTL). Furthermore, PGD losses escalate significantly with increasing albedo due to radiative/SRH recombination. Ultimately, we achieve a PGD of 30.45–39.90 mW/cm2 by mitigating all recombination channels, representing a 13.14–21.87 % increase over the initial device. This study offers guidance for developing bifacial 2T TSCs with improved efficiency.

Hybrid Two‐Step Inkjet‐Printed Perovskite Solar Cells

Perovskite photovoltaics are on their way to commercialization, but crucial advancements are still required to realize scalable and reliable fabrication processes Concerning solution processing of perovskite top solar cells, the hybrid two‐step process offers an auspicious combination of good thin‐film formation control, even on textures, and high power conversion efficiencies (PCEs). Herein, a scalable fabrication process that consists of a hybrid two‐step process and combines evaporated PbI2 with inkjet‐printed organic precursor materials is addressed. It is shown that optimizing the printing parameters enables high PCEs, high reproducibility, and the potential for conformal growth on textured silicon. The perovskite films are free of macroscopic drying effects and omit the use of toxic solvents. To achieve optimal conversion, the morphology of the PbI2 thin film and the selected resolution in the printing process are decisive. To facilitate intermixing and enable stoichiometry, a dimethyl sulfoxide vapor treatment is introduced to increase the PbI2 porosity. Reproducible PCEs are demonstrated with champion devices showing 18.2% which are on par with spin‐coated counterparts. In the results, it is demonstrated that the hybrid two‐step process with an inkjet‐printed second step is a promising scalable process for reliable and high‐quality perovskite deposition even on texture, thereby paving the path toward industrialization.

Long-term performance and degradation analysis of a 5 MW solar PV plant in the Andaman & Nicobar Islands

Renewable energy is being advocated as a new strategy in response to rising energy demand and global climate change. Solar photovoltaic technology is of great significance to climatic conditions due to the good solar intensity and availability to generate energy. In this paper, the 10-year operating performance of a 5 MW solar PV plant installed in tropical climate of the Andaman and Nicobar Islands was analysed. In 2015, the PV plant achieved its highest electricity production of 7216 MWh, while its lowest, 4757 MWh, was observed in 2022.The maximum performance ratio was recorded as 84.28 % in 2016 due to lower operating cell temperature whereas the maximum CUF as 16.17 % was recorded in 2015. The highest module, inverter and system efficiency for the ten year was observed 12.03 %, 97.64 % and 11.75 % respectively in year 2016. In 2014, the highest values for reference yield, array yield, and final yield were recorded as 4.92, 4.08, and 3.98 kWh/kW/day, respectively. Higher capture losses were observed in the plant over the year which varies upto 1.65 h/d. The plant exhibited a degradation rate of 1.99 % per annum, determined by employing an initial PR of 80.03 %, which declined to 64.11 % by 2022. Degradation analysis of the present system was also performed using visual inspection technique. Mostly found defects in plant was corrosion, delamination of encapsulant material, browning of cell material, burn mark on the back of module, milky patterns, cracks in top facing glass and solar cells. Since, the plant is located in the coastal area, it was seen that the plant is facing a severe issue of algae growth. Some PV modules were covered by more than 90 % algae which significantly contribute in capture losses.

Exploring the Potential of Pure Germanium Kesterite for a 2T Kesterite/Silicon Tandem Solar Cell: A Simulation Study.

Recently, the development of tandem devices has become one of the main strategies for further improving the efficiency of photovoltaic modules. In this regard, combining well-established Si technology with thin film technology is one of the most promising approaches. However, this imposes several limitations on such thin film technology, such as low prices, the absence of scarce or toxic elements, the possibility to tune optical properties and long lifetime stability. Therefore, to show the potential of kesterite/silicon tandems, in this work, a 2 terminal (2T) structure using pure germanium kesterite was simulated with combined SCAPS and transfer matrix methods. To explore the impact of individual modifications, a stepwise approach was adopted to improve the kesterite. For the bottom sub cell, a state-of-the-art silicon PERC cell was used with an efficiency of 24%. As a final result, 19.56% efficiency was obtained for the standalone top kesterite solar cell and 28.6% for the tandem device, exceeding standalone silicon efficiency by 4.6% and justifying a new method for improvement. The improvement observed could be attributed primarily to the enhanced effective lifetime, optimized base doping, and mitigated recombination at both the back and top layers of the CZGSSe absorber. Finally, colorimetric analysis showed that color purity for such tandem structure was low, and hues were limited to the predominant colors, which were reddish, yellowish, and purple in an anti-reflective coating (ARC) thickness range of 20-300 nm. The sensitivity of color variation for the whole ARC thickness range to electrical parameters was minimal: efficiency was obtained ranging from 28.05% to 28.63%.

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.

Proposal and Design of Flexible All-Polymer/CIGS Tandem Solar Cell.

Tandem solar cells (TSCs) have attracted prodigious attention for their high efficiency, which can surmount the Shockley-Queisser limit for single-junction solar cells. Flexible TSCs are lightweight and cost-effective, and are considered a promising approach for a wide range of applications. In this paper, a numerical model, based on TCAD simulation, is presented to assess the performance of a novel two-terminal (2T) all-polymer/CIGS TSC. To confirm the model, the obtained simulation results were compared with standalone fabricated all-polymer and CIGS single solar cells. Common properties of the polymer and CIGS complementary candidates are their non-toxicity and flexibility. The initial top all-polymer solar cell had a photoactive blend layer (PM7:PIDT), the optical bandgap of which was 1.76 eV, and the initial bottom cell had a photoactive CIGS layer, with a bandgap of 1.15 eV. The simulation was then carried out on the initially connected cells, revealing a power conversion efficiency (PCE) of 16.77%. Next, some optimization techniques were applied to enhance the tandem performance. Upon treating the band alignment, the PCE became 18.57%, while the optimization of polymer and CIGS thicknesses showed the best performance, reflected by a PCE of 22.73%. Moreover, it was found that the condition of current matching did not necessarily meet the maximum PCE condition, signifying the essential role of full optoelectronic simulations. All TCAD simulations were performed via an Atlas device simulator, where the light illumination was AM1.5G. The current study can offer design strategies and effective suggestions for flexible thin-film TSCs for potential applications in wearable electronics.

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.

High‐Efficiency Cs‐Based Perovskite‐Silicon Tandem Solar Cells—A Modeling Study

Current studies stipulate that the performance efficiency of photovoltaic cells can be increased by incorporating a tandem architecture into the device configuration. This work includes an assessment of the photovoltaic performance parameters and optimization of the cesium lead iodide (CsPbI3)–silicon (Si) tandem solar cells (TSC) by applying the SCAPS 1D tool. The two terminal (2‐T) monolithic TSC device configuration with a top CsPbI3 perovskite solar cell (PSC) consisting of IGZO as the electron transport layer material (ETL) and CuSbS2 as the hole transport layer material (HTL) and a bottom c‐Si solar cell exhibits a fill factor (FF) and power conversion efficiency (PCE) of 73.16% and 27.07%, respectively, by establishing the current matching condition, while in the four terminal (4‐T) stacked layer configuration, the device exhibits a PCE of 30.68%. The device acquires this high PCE after the optimization of the thickness, dopant density, and defect density of the perovskite light active material and Si.

Spectrometric Characterization of Monolithic Perovskite/Silicon Tandem Solar Cells

In monolithic perovskite/silicon tandem solar cells, it is important to know which subcells are limiting the overall current to adapt the perovskite absorber thickness and bandgap accordingly. The current matching situation is usually analyzed by integrating measured external quantum efficiencies. However, this method can lead to significant errors and misinterpretations if metastable perovskite solar cells are involved. Herein, spectrometric characterization is presented as an alternative approach avoiding these errors. Current–voltage curves are recorded under different spectral conditions. Spectral irradiance settings are varied in a systematic way from redshifted spectra (the perovskite top solar cell limits the current) to blueshifted spectra (the silicon bottom solar cell limits the current) around the air mass 1.5 global (AM1.5G) spectrum. This method not only allows for accurate determination of the current matching point, but also gives quantitative insight in the behavior of the single subcells and their influence on the tandem performance. As different current mismatching also influences other global cell parameters, an example is presented where the current loss due to the current mismatch is partly compensated by a strong fill factor increase when the silicon solar cell limits the current, resulting in a high‐power output also at the AM1.5G condition.

Laminated Monolithic Perovskite/Silicon Tandem Photovoltaics

AbstractPerovskite/silicon tandem photovoltaics have attracted enormous attention in science and technology over recent years. In order to improve the performance and stability of the technology, new materials and processes need to be investigated. However, the established sequential layer deposition methods severely limit the choice of materials and accessible device architectures. In response, a novel lamination process that increases the degree of freedom in processing the top perovskite solar cell (PSC) is proposed. The very first prototypes of laminated monolithic perovskite/silicon tandem solar cells with stable power output efficiencies of up to 20.0% are presented. Moreover, laminated single‐junction PSCs are on par with standard sequential layer deposition processed devices in the same architecture. The numerous advantages of the lamination process are highlighted, in particular the opportunities to engineer the perovskite morphology, which leads to a reduction of non‐radiative recombination losses and and an enhancement in open‐circuit voltage (Voc). Laminated PSCs exhibit improved stability by retaining their initial efficiency after 1‐year aging and show good thermal stability under prolonged illumination at 80 °C. This lamination approach enables the research of new architectures for perovskite‐based photovoltaics and paves a new route for processing monolithic tandem solar cells even with a scalable lamination process.

Device simulation of quasi-two-dimensional perovskite/silicon tandem solar cells towards 30%-efficiency

Perovskite/silicon (Si) tandem solar cells have been recognized as the next-generation photovoltaic technology with efficiency over 30% and low cost. However, the intrinsic instability of traditional three-dimensional (3D) hybrid perovskite seriously hinders the lifetimes of tandem devices. In this work, the quasi-two-dimensional (2D) (BA)2(MA) n – 1Pb n I3n + 1 (n = 1, 2, 3, 4, 5) (where MA denotes methylammonium and BA represents butylammonium), with senior stability and wider bandgap, are first used as an absorber of semitransparent top perovskite solar cells (PSCs) to construct a four-terminal (4T) tandem devices with a bottom Si-heterojunction cell. The device model is established by Silvaco Atlas based on experimental parameters. Simulation results show that in the optimized tandem device, the top cell (n = 4) obtains a power conversion efficiency (PCE) of 17.39% and the Si bottom cell shows a PCE of 11.44%, thus an overall PCE of 28.83%. Furthermore, by introducing a 90-nm lithium fluoride (LiF) anti-reflection layer to reduce the surface reflection loss, the current density (J sc) of the top cell is enhanced from 15.56 mA/cm2 to 17.09 mA/cm2, the corresponding PCE reaches 19.05%, and the tandem PCE increases to 30.58%. Simultaneously, in the cases of n = 3, 4, and 5, all the tandem PCEs exceed the limiting theoretical efficiency of Si cells. Therefore, the 4T quasi-2D perovskite/Si devices provide a more cost-effective tandem strategy and long-term stability solutions.

High-Efficiency p-n Homojunction Perovskite and CIGS Tandem Solar Cell

Efficiency has been known to be one of the most important factors in a solar cell. This article presents the results of a simulation performed on a perovskite/CIGS dual-junction solar cell. In this report, first, a top solar cell consisting of a perovskite absorber layer is simulated using the pn-junction; the separation and transfer of carriers in this structure are done by the internal electric field. The pn-junction has a discharge area smaller than the pin-junction, which increases carrier recombination and reduces optical losses. The perovskite band gap of 1.9 eV is considered, and the efficiency is 21.65% using the Au electrode. Then, the bottom solar cell is fabricated with a CIGS absorbent layer with a 1.4 eV band gap and an efficiency of 11.46%. After simulating and evaluating the performance of the top and bottom solar cells independently, both cells were simulated and examined for the dual-junction state. Since the perovskite and CIGS band gaps are both adjustable, these two materials can act as a proper partner for an absorbent layer in a dual-junction solar cell. In this structure, instead of the usual connection of p-i-n and n-i-p perovskite, n-type and p-type homojunction perovskite connection is used, in which the transfer and separation of carriers are done by an internal electric field. Due to the fact that in this structure, the discharge area is smaller, the recombination of carriers is increased, and the light losses are reduced, which will increase the absorption and efficiency of the cell. The results show that in the tandem design, we encounter an increase in Voc (2.25 V), thus increasing the efficiency of the solar cell (30.71%).

Minimizing Open‐Circuit Voltage Loss in Perovskite/Si Tandem Solar Cells via Exploring the Synergic Effect of Cations and Anions

In article number 2100119, Zeguo Tang, Yongzhe Zhang, and co-workers discuss how adopting a perovskite/Si tandem solar cell structure is an effective approach to break the S–Q limit of single-junction solar cells. Minimizing the open-circuit voltage loss of the top perovskite solar cell is critical to achieving a high efficiency of the tandem cell because the open-circuit voltage of the bottom Si cell is fixed, relatively, and the addition of MACl plays such a role.

Efficient 2T CsKPb(IBr)3—Tin Incorporated Narrow Bandgap Perovskite Tandem Solar Cells: A Numerical Study with Current Matching Conditions

AbstractThis study numerically investigates a highly efficient tandem‐structured and, perovskite‐perovskite model solar cells using the solar cell simulator capacitance software (), consisting of wide‐bandgap top potassium incorporated inorganic cesium‐based perovskite cell () and narrow‐bandgap bottom tin incorporated perovskite cells (and ). The study explores and optimizes the front and rear perovskite absorber layer parameters (especially thickness) and current matching conditions ideal for tandem device performance. The simulated top standalone inorganic solar cell parameters yield a power conversion efficiency of over 13% (for all models), while the bottom perovskite devices simulated with filtered spectrum yield an efficiency of 14.17% for , 8.54% for , and 13.30% for , respectively. The study and quantification of the current matching points for the tandem configuration provide some insight into the device's performance, which is beneficial for its efficiency enhancement. The resultant simulated optimized tandem cells offer a maximum efficiency of 21% for model, 17.5% for model, and 20% for model, respectively, with improved parameters.

In2O3:H-Based Hole-Transport-Layer-Free Tin/Lead Perovskite Solar Cells for Efficient Four-Terminal All-Perovskite Tandem Solar Cells.

Narrow-band gap (NBG) Sn-Pb perovskites with band gaps of ∼1.2 eV, which correspond to a broad photon absorption range up to ∼1033 nm, are highly promising candidates for bottom solar cells in all-perovskite tandem photovoltaics. To exploit their potential, avoiding optical losses in the top layer stacks of the tandem configuration is essential. This study addresses this challenge in two ways (1) removing the hole-transport layer (HTL) and (2) implementing highly transparent hydrogen-doped indium oxide In2O3:H (IO:H) electrodes instead of the commonly used indium tin oxide (ITO). Removing HTL reduces parasitic absorption loss in shorter wavelengths without compromising the photovoltaic performance. IO:H, with an ultra-low near-infrared optical loss and a high charge carrier mobility, results in a remarkable increase in the photocurrent of the semitransparent top and (HTL-free) NBG bottom perovskite solar cells when substituted for ITO. As a result, an IO:H-based four-terminal all-perovskite tandem solar cell (4T all-PTSCs) with a power conversion efficiency (PCE) as high as 24.8% is demonstrated, outperforming ITO-based 4T all-PTSCs with PCE up to 23.3%.

Technoeconomically competitive four-terminal perovskite/graphene-silicon tandem solar cells with over 20% efficiency

Perovskite/Silicon (PS) tandem solar cells have attracted much interest over recent years. However, the most popular crystalline silicon solar cells utilized in tandems require complicated fabrication processes mainly including texturization, diffusion, passivation and metallization, which takes up much cost in photovoltaic market. Here, we report a facile graphene/silicon (Gr/Si) solar cell featuring of low-temperature (≤200 °C) processing and an efficiency of 13.56%. For reducing the heat dissipation loss of high energy photon, the perovskite solar cell (PSC) with a wide band gap of 1.76 eV was adopted as the top cell for the tandem. To reduce the loss of parasitic absorption in hole transport layers (HTLs), thickness of Spiro-OMeTAD is re-optimized by compromising the efficiency and the optical transmittance of the devices. As a result, the semitransparent top perovskite solar cell yields a highest efficiency of 13.35%. Furthermore, we firstly achieved a low-temperature-processed four-terminal (4-T) perovskite/graphene-silicon (PGS) heterojunction tandem solar cell with the efficiency of 20.37%. The levelized cost of electricity (LCOE) of PGS 4-T modules were estimated to a competitive price, exhibiting much greater potential for practical application compared to that of PS 4-T modules.

Examination of Suitable Bandgap Grading of Cu(InGa)Se2 Bottom Absorber Layers for Tandem Cell Application

A high‐efficiency tandem solar cell comprises of top and bottom solar cells. The bottom cell has a bandgap of ≈1.1 eV and is designed to absorb longer wavelengths of photons. A Cu(InGa)Se2 (CIGS) is one of the candidates for a bottom solar cell, but its bandgap is not constant and is graded with depth. This study discusses suitable bandgap grading of CIGS cells for bottom cell applications. Three CIGS devices with different bandgap gradings are prepared for bottom cell evaluation. One device has a single‐back‐graded bandgap type whereas the others have double‐graded bandgap types, which have been used for high‐efficiency CIGS devices. The three CIGS devices exhibit similar conversion efficiencies of ≈20% but different solar cell parameters, due to their different shapes of bandgap grading. For the bottom cell evaluations, current–voltage measurements are performed using 720 nm (≈1.72 eV) and 800 nm (≈1.55 eV) long‐pass filters. It is found that a CIGS device with a double‐graded bandgap is unsuitable and/or shows reduced performance with a decreased top cell bandgap. By contrast, CIGS devices with a single‐back‐graded bandgap can be adopted as a bottom cell under top cell bandgaps of both ≈1.55 and ≈1.72 eV.

Thermodynamic limit of tandem solar cells under different solar spectra and their perovskite top solar cell

Abstract Thermodynamic (detailed balance) limits of single-junction and tandem-type solar cells are calculated under different solar spectra, which are spectra of blackbody (6000 K), air mass 0, air mass 1.5 global (1.5G), and air mass 1.5 direct (1.5D). The solar cells are described by blackbody under room temperature of 298.15 K. It is disclosed that optimized bandgaps of single-junction solar cells with the highest conversion efficiencies of 31.6, 30.6, 33.7 and 33.1% are 1.29, 1.25, 1.34, and 1.34 eV under illuminations of blackbody (6000 K), air mass 0, air mass 1.5G, and air mass 1.5D, respectively. Conversion efficiencies of 43.2, 42.2, 45.5, and 45.1% are further increased for double-junction tandem solar cells with optimized bandgaps of bottom and top cells under spectra of blackbody (6000 K), air mass 0, air mass 1.5G, and air mass 1.5D, respectively. Moreover, detailed balance limits of tandem solar cells with perovskite top cells with bandgap range of 1.60–1.63 eV were realized with high conversion efficiency, when bandgap values of bottom cells are optimized in a range of 0.8–1.01 eV, and at 1.1 eV. It is also disclosed that the optical matching between top cell absorber and bottom cell absorber should be optimized for the high cell performances.

Backside light management of 4-terminal bifacial perovskite/silicon tandem PV modules evaluated under realistic conditions.

Perovskite/silicon tandem modules have recently attracted growing interest as a potential candidate for new generations of solar modules. Combined with a bifacial configuration it can lead to considerable energy yield improvement in comparison to conventional monofacial tandem solar modules. Optical modeling is crucial to analyze the optical losses of perovskite/silicon solar modules and achieve efficient light management. In this article we study the optical properties of four-terminal bifacial tandem modules, using metal-halide perovskite top solar cell and a conventional industrial crystalline silicon PERC bottom solar cell. We propose a method to analyze bifacial gains, improve back side light management and challenge it under realistic spectral conditions at several locations with various albedos. We show that both optimized designs for the back side show comparable advantages at all locations. These results are a good sign for the standardization of bifacial four-terminal perovskite/silicon modules.

Semitransparent perovskite solar cells with ultrathin silver electrodes for tandem solar cells

Tandem solar cells with top perovskite solar cells (PSCs) have attracted great attention due to the rapid progress in power conversion efficiency (PCE). Ultrathin silver (Ag) metals with low percolation threshold are promising candidates as transparent electrodes for semitransparent PSCs. In this work, continuous Ag films with percolation threshold lower than 6 nm were realized through Cu seed layer, which guaranteed not only excellent conductivity but also broadband transparency. As a result, semitransparent PSCs with 6 nm Ag electrodes exhibited PCE of 14.5%, maintaining 88% performance of the opaque PSCs. Moreover, the average transmittance of semitransparent PSCs in the range of 800–1200 nm was improved to 58.6% using zinc oxide as optical coupling layer, promising near infrared light absorption by bottom solar cells. Ultimately, four-terminal tandem solar cell using semitransparent PSC and homogenous crystalline silicon solar cell was demonstrated. Furthermore, the strategies of using 5 nm Ag electrodes combined with Ag grids, and optical coupling layers with higher refractive index, were suggested to further increase the PCE of tandem solar cells. The proposed ultrathin Ag transparent electrodes are ease of fabrication as well as good optoelectrical properties, which are promising for application in semitransparent PSCs and tandem solar cells.