Theoretical Power Conversion Efficiency Research Articles

Efficiency enhancement of novel ITO/ZnSe/CNTs thin film solar cell

This study presents a novel photovoltaic cell design utilizing a layered structure of Indium Tin Oxide (ITO), Zinc Selenide (ZnSe), and Carbon Nanotubes (CNTs) for enhanced solar energy conversion. We employed the Solar Cell Capacity Simulator (SCAPS-1D) to model and optimize the device under AM 1.5 spectrum conditions. Our simulations systematically investigated the influence of key parameters including layer thicknesses, doping concentrations, temperature, back contact work function, and parasitic resistances on cell performance. The optimized structure demonstrated a theoretical power conversion efficiency of 29.91%, with an open-circuit voltage (Voc) of 799 mV, a short-circuit current density (Jsc) of 43.49 mA/cm², and a fill factor (FF) of 86.02%. These promising results are attributed to the synergistic combination of CNTs' broad spectral absorption, ZnSe's effective charge separation, and optimized layer properties. We found that the CNT absorber layer's doping concentration significantly impacted cell performance, with an optimal value of 10¹⁷ cm⁻³. The ZnSe buffer layer thickness showed minimal effect on efficiency within the studied range. Temperature increases from 300K to 400K led to a significant efficiency drop from 33.97% to 24.65%, primarily due to Voc reduction. While these results represent idealized conditions and upper theoretical limits, they provide valuable insights for the potential of CNT-based solar cells. This study offers a roadmap for future experimental work in high-efficiency thin-film photovoltaics, highlighting the promise of novel material combinations and the importance of device architecture optimization.

23.6 % Efficient perovskite-organic tandem photovoltaics enabled by recombination layer engineering

Recombination layers are crucial in achieving high power conversion efficiency (PCE) in tandem solar cells. Here, we report the development and optimization of recombination junctions for high PCE perovskite-organic tandem solar cells (PO-TSCs). We choose a wide bandgap perovskite (1.79 eV) for the front subcell and a narrow bandgap (1.36 eV) organic bulk heterojunction (BHJ) for the rear subcell. The optimal thicknesses of the perovskite and organic layers were determined to be 260 and 100 nm, respectively, based on the analysis of Transfer-Matrix optical simulations. Our results demonstrate that the optimal recombination layer consists of an ultrathin layer of indium zinc oxide IZO (∼ 2 nm) deposited on MoOx/2PACz, which delivers a PCE of 23.6 %. This high PCE is attributed to the high transparency of the recombination layer in the NIR spectra region and the low sheet resistance of IZO. Furthermore, we provide a theoretical analysis of the potential efficiency of PO-TSCs as a function of front and rear subcells and predict a maximum theoretical PCE value of more than 36 %. Our work highlights the importance of selecting the proper recombination layer design for achieving high-performance PO-TSCs.

Boosting the Performance of Diketopyrrolopyrrole-Triphenylamine-Based Organic Solar Cells via π-Linker Engineering.

The design and development of novel and efficient donor-π-acceptor (D-π-A) type conjugated systems has attracted substantial interest in the field of organic electronics owing to their intriguing properties. In this paper, we have designed seven new and efficient D-π-A type conjugated systems (M1-M7) by a variety of π-linkers with triphenylamine (TPA) as the electron donor and diphenyldiketopyrrolopyrrole (DPP) as the electron acceptor using density functional theory (DFT) formalism for organic solar cells (OSCs). The π-linker has been substituted between the donor and acceptor for efficient electron transfer. Here, our primary focus is on narrowing the highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, electronic transition, charge transfer rate, reorganization energies, and the theoretical power conversion efficiencies (PCEs). Our study reveals that the designed compounds exhibit excellent charge transfer rates. The absorption properties of the compounds have been examined using the time-dependent density functional theory (TD-DFT) method. The TD-DFT study shows that compound M2 possesses the highest absorption maxima with a maximum bathochromic shift. For a better understanding of the electron transport process of our designed compounds, we have designed donor/acceptor (D/A) blends, and each of the developed blends (FREA/M1-M7) can encourage charge carrier separation. According to the photovoltaic performance of the D/A blends, compound FREA-M2, which has a theoretical PCE of 16.53%, is the most appealing choice for use in OSCs. We expect that by thoroughly examining the relationship between structure, characteristics, and performance, this work will serve as a roadmap for future research and development of TPA-DPP-based photovoltaic materials.

Enhancing photovoltaic efficiency: Integrating graphene and advanced interface layers to reduce the recombination losses in lead-free MASnI3 perovskite solar cells

Perovskite solar cells have attracted significant attention within the scientific community due to their rapidly advancing performance. In particular, inorganic perovskite devices are renowned for their remarkable performance and enduring stability. This study introduces a device optimization process guided by modeling to fabricate high-efficiency perovskite solar cells using lead-free n-i-p methyl ammonium tin iodide (MASnI3) materials. We thoroughly examined the impact of both the absorber and interface layers on the optimized structure. Our approach involves employing graphene as the interface layer between the hole transport and absorber layers. Additionally, we utilized ZnO:Al and 3C-SiC as interface layers between the absorber and electron transport layers. The optimization process entails adjusting the thickness of the absorber layer and interface layers while minimizing defect densities. The proposed optimized device structure, FTO/TiO2/ZnO:Al/MASnI3/Graphene/Cu2O/Au, demonstrates theoretical power conversion efficiencies of 30.43 %, fill factors of 89.30 %, a current density of 29.40 mA/cm2, a voltage of 1.1591 V, and a maximum quantum efficiency of 93 %. This research underscores the potential tin-based absorber layer MASnI3 as a non-toxic perovskite material for applications in sustainable energy from renewable sources.

Modulation of optoelectronic properties in Cl and Br doped GUASnI[formula omitted] based perovskite solar cells: A Density Functional Theory analysis

Partial substitution of I by Cl or Br improves the performance of hybrid lead halide perovskite materials. Here, a systematic density functional theory (DFT)-based investigation has been carried out in some mixed halide perovskites having the general formula GUASnX3−yXy′, where GUA = guanidinium cation, X = iodine (I), X′ = chlorine (Cl) or bromine (Br), and y = 0, 1, 1.5, and 2. Results obtained have been compared with the pure iodine-based compound to understand the impact of doping ratio on physical, optoelectronic, and photovoltaic properties of the hybrid halide perovskite materials. From the analysis, it has been observed that all the designed compounds form thermodynamically stable three-dimensional perovskite structures. In addition, the designed compounds possess band gap (Eg) values within the range of 0.91-2.33 eV. However, Eg decreases with an increase in iodine content. Complex dielectric function and absorption coefficient analysis led to the conclusion that all the investigated compounds exhibit absorption maxima in the visible range of the electromagnetic spectrum. Moreover, photovoltaic performance analysis reveals that GUASnI3 exhibits the highest theoretical power conversion efficiency (PCE) of 27.78% among the studied compounds. The study also shows that the pure iodine-based compound is superior to the corresponding mixed halide compounds in terms of their optoelectronic and photovoltaic properties. Hence, it is expected that the study will provide researchers a basis to further investigate mixed halide perovskite based materials in the future.

All-perovskite tandem solar cells: from fundamentals to technological progress.

Organic-inorganic perovskite materials have gradually progressed from single-junction solar cells to tandem (double) or even multi-junction (triple-junction) solar cells as all-perovskite tandem solar cells (APTSCs). Perovskites have numerous advantages: (1) tunable optical bandgaps, (2) low-cost, e.g. via solution-processing, inexpensive precursors, and compatibility with many thin-film processing technologies, (3) scalability and lightweight, and (4) eco-friendliness related to low CO2 emission. However, APTSCs face challenges regarding stability caused by Sn2+ oxidation in narrow bandgap perovskites, low performance due to V oc deficit in the wide bandgap range, non-standardisation of charge recombination layers, and challenging thin-film deposition as each layer must be nearly perfectly homogenous. Here, we discuss the fundamentals of APTSCs and technological progress in constructing each layer of the all-perovskite stacks. Furthermore, the theoretical power conversion efficiency (PCE) limitation of APTSCs is discussed using simulations.

Ga and In-based hybrid halide perovskites as an alternative to Pb: a first principles study.

Lead-free hybrid halide perovskites have gained much attention in the field of photovoltaics due to their non-toxicity, stability and unique photo-physical properties. Sn and Ge-based ABX3 perovskites have been widely studied due to their similar electronic properties to Pb-based materials. However, the unstable oxidation state of Sn is a major challenge for the commercialization of this class of materials. To overcome this problem, here, we have designed a series of novel Ga and In-based A3B2X9-type perovskite materials incorporating the methylammonium (MA) organic cation in the A site and I- as the halide ion in the X site. In this regard, we have investigated different structural, electronic, optical and photovoltaic properties by employing the density functional theory formalism. The formation of a stable three dimensional perovskite structure is determined by the observed values of tolerance factor (TF) and octahedral factor (μ). The observed negative values of formation enthalpy manifest that our studied materials are also thermodynamically stable. The obtained band gap values reveal that our designed perovskite materials can act as semiconducting materials for application in photovoltaics. We have also investigated the optical properties of our studied materials and the observed values of dielectric function and absorption coefficient in the visible range of the electromagnetic spectrum indicate their excellent photo absorption. The observed theoretical power conversion efficiency (PCE) values reveal that (MA)3In2I9 (13.82%) and (MA)3 (Ga.50In.50)2I9 (12.8%) can be chosen as potential candidates for application in perovskite-based photovoltaics. This research provides a pathway for the development of less toxic and efficient semiconducting materials, offering exciting prospects for their utilization in optoelectronics and contributing to the ongoing efforts to advance sustainable energy technologies.

Chalcogenide Perovskite, An Emerging Photovoltaic Material: Current Status and Future Perspectives

AbstractChalcogenide perovskite materials came into the picture of photovoltaic technology since 2015. Their admirable structural, electronic and optical properties make them highly promising for solar energy conversion. They have immense potential to solve the stability and toxicity issues of conventional perovskite solar cells. The maximum theoretical power conversion efficiency reported for them is about 30 % which is similar to CH3NH3PbI3 perovskite material. However their application in photovoltaics is limited by several challenges. In this review, we tried to provide an overview of the structural features of the chalcogenide perovskite materials and critically highlighted computational and synthetic accomplishments in this area. Various techniques developed for synthesizing these materials so far, have also been summarized. Along with that, the challenges associated in designing these materials for improved optoelectronic properties are also addressed. Serious research efforts are urgently needed for the realization of the dream of chalcogenide perovskite material based solar cells in terms of optimization of optoelectronic properties, synthetic cost, processing of thin films and application in tandem solar cell devices. This review may facilitate further progress in chalcogenide perovskite material based thin film solar cell in the future.

Optical–electrical simulation and optimization of an efficient lead-free 2T all perovskite tandem solar cell

The characteristics of a lead-free all perovskite tandem solar cell (P-TSC) are studied in this study. All P-TSCs were developed with the goal of breaking through the theoretical power conversion efficiency (PCE) limit for single-junction (SJ) perovskite solar cells (PSCs) established by Shockley and Queisser. Solving the toxicity problem in lead-containing sub-cells is essential for the continued growth of all P-TSCs. Here, we first present a coupled three-dimensional (3D) optical–electrical simulation of two lead-free SJ MAGeI3(Eg=1.9eV) and MASnI3(Eg=1.3eV) PSCs. The results showed that the PCE of the SJ-wide bandgap (WBG) and SJ-narrow bandgap (NBG) PSCs is 19.59% and 15.57%, respectively. Next, a two-terminal (2T) eco-friendly all P-TSC with combines these two solar cells has been designed, where the MAGeI3-PSC serves as the top sub-cell and the MASnI3-PSC serves as the bottom sub-cell. By establishing the current matching condition between two sub-cells in the 2T structure, the matched short-circuit current density (Jsc) and PCE are obtained 12.30mA/cm2 and 28.46%, respectively. Herein, a 299 nm-thick NBG-absorber layer and a 200 nm-thick WBG-absorber layer are required. In order to increase the matched Jsc and PCE and decrease the required NBG-absorber layer thickness, the parasitic absorption and reflection losses are minimized by selecting the best materials for the transparent conductive oxide (TCO) front contact and interconnecting (IC) layers, as well as the addition of an anti-reflection (AR) layer at the air/device interface as light management strategies. The results indicate that, under the current matching condition, improving the structure would lead to in a 76 nm reduction in the NBG-absorber layer’s required thickness and a 16.44% increase in PCE. Finally, we suggested the optimized 2T non-Pb all P-TSC with a high PCE of 33.14% that is environmentally safe.

Exploring A‐Site Cation Variations in Dion–Jacobson Two‐Dimensional Halide Perovskites for Enhanced Solar Cell Applications: A Density Functional Theory Study

The exceptional photophysical and electronic properties of 2D hybrid perovskites possess potential applications in the field of solar energy harvesting. The present work focuses on the two systems, exhibiting the Dion–Jacobson phase of 2D perovskite consisting of methylammonium (MA) and formamidinium (FA) cations at A‐site and 3‐(aminomethyl)pyridinium (3AMPY) as ring‐shaped organic spacer. Altering A‐site cations creates a distortion of inorganic layers and hydrogen bond interactions. It has been noted that the angles of Pb–I–Pb and I–Pb–I are more symmetric (close to 180°) for (3AMPY)(MA)Pb2I7 compared to (3AMPY)(FA)Pb2I7 and result in increase of bandgap from 1.51 to 1.58 eV. This further leads to a significant difference in Rashba splitting energy under the influence of spin‐orbit coupling effects, where the highest splitting (36 meV) is calculated for conduction band edge of the (3AMPY)(FA)Pb2I7, suggesting the promising applications toward spintronics. The calculated absorption spectra cover the range from 300 to 450 nm, indicating significant optical activity of 2D (3AMPY)(MA)Pb2I7 and (3AMPY)(FA)Pb2I7 in the visible and ultraviolet regions, which bodes well for their application in advanced optoelectronic devices. The bandgap and high absorption coefficients present more than 30% of theoretical power conversion efficiency for both systems, as calculated from the spectroscopic‐limited maximum efficiency.

Electronic structure, theoretical power conversion efficiency, and thermoelectric properties of bismuth-based alkaline earth antiperovskites.

This research paper investigates the properties and potential applications of antiperovskite materials. Antiperovskites are a class of materials with a unique crystal structure, where the central atom is surrounded by a cage of anions. We review recent research on antiperovskite-based materials for energy storage, photovoltaics, catalysis, and sensors. We discovered that these materials display direct band gap semiconductors, strong absorption in the visible (VIS), ultra-violet (UV), and near infrared regions (NIR) based on their fundamental features, which is the most admirable quality that may be found in many optoelectronic devices. Both mechanical and thermodynamic stability have been confirmed for these materials. We discovered that these materials exhibit high figures of merit through the calculation of transport properties, which makes them a promising candidate for thermoelectric devices. It is anticipated that the proposed material BiPMg3, which has a theoretical efficiency of 11.5%, will make a suitable photovoltaic absorber. This paper highlights the potential of these materials for future technological advancements. Herein, we have used most authentic techniques to compute fundamental physical properties of these antiperovskites. Full-potential linear augmented plane wave (FP-LAPW) method has been used to investigate electronic, magnetic, optical properties, and make antiperovskites attractive for a variety of applications. In light of its implementation, we have checked the theoretical power conversion efficiency by first principles spectroscopic screening methodology, and inspect the fundamental physical parameters of antiperovskites, focusing on their potential as functional materials for energy and information technologies.

A Review on the Fundamental Properties of Sb2Se3-Based Thin Film Solar Cells

There has been a recent surge in interest toward thin film-based solar cells, specifically new absorber materials composed by Earth-abundant and non-toxic elements. Among these materials, antimony selenide (Sb2Se3) is a good candidate due to its peculiar properties, such as an appropriate bandgap that promises a theoretical maximum power conversion efficiency of 33% and an absorption coefficient of around 105 cm−1, enabling its use as a thin film absorber layer. However, charge carrier transport has been revealed to be problematic due to its cumbersome structure and the lack of a doping strategy. In this work, we aim to provide a clear picture of the state-of-the-art regarding research on Sb2Se3-based solar cells and its prospects, from the successful achievements to the challenges that are still to be overcome. We also report on the key parameters of antimony selenide with a close focus on the different characteristics associated with films grown from different techniques.

Insight into conduction band density of states at c-Si/TiO2 interface for efficient heterojunction solar cell

Carrier selective solar cell has become one of the hot spots in the area of Si solar cell. The proposed architecture FTO/TiO2/c-Si/i-a-Si:H/Cu2O/back contact studied through simulation demonstrates a power conversion efficiency of 20.03%. This study is the first to report detailed exploration of effect of the conduction band density of states on the efficiency of Si solar cell. Through optimization, the conduction band density of state (1017 cm-3) drastically increases the power conversion efficiency from 18% (at 1021 cm-3) to 21.25% (at 1017 cm-3) i.e., an improvement of 18% relatively. Along with this, the parameters like absorber layer thickness, absorber’s defect density, thickness of electron transport layer and interface defect density are also optimized. Moreover, the charge transport properties and the impact of the Schottky barrier height at c-Si/TiO2 interface on band alignment is studied. After optimization of various physical parameters such as thickness (100 μm), conduction band density of states (1017 cm-3) and defect concentration (1010 cm−3) of c-Si layer, thickness of TiO2 layer (20 nm) and interface defect density at c-Si/TiO2 junction (1010 cm−2), a short-circuit current of 38.11 mA cm−2, open-circuit voltage of 0.84 V, fill factor of 85.99% is obtained, leading to an enhanced theoretical power conversion efficiency of 27.77%.

A first‐principles investigation into the rational design of Sn‐halide perovskite materials as an alternative to Pb‐based perovskites

AbstractThe development of Pb‐free alternatives for perovskite‐based photovoltaics is extremely important due to the toxicity of Pb to the environment. Sn‐based organic inorganic hybrid halide perovskites are considered to be the most suitable alternative to Pb‐based ABX perovskites due to their similar optoelectronic properties. The selection of A site cation in ABX type perovskites is crucial for favorable structural and mechanical properties. Using first principle methods, we have designed and investigated Sn–I based hybrid halide perovskite materials with different organic cations mixed in equal proportions. Observed tolerance (TF) and octahedral factors () indicate the formation of stable three‐dimensional perovskite structure. Our studied materials also exhibit thermodynamic stability due to the negative value of their formation energies. Observed band gap values indicate the semiconducting nature of our studied perovskite materials. Calculated optical properties indicate that all of the compounds exhibit suitable dielectric functions and absorption coefficients in the visible range of the electromagnetic spectrum. The observed highest value of theoretical power conversion efficiency of MA‐AMSnI (11.24%) indicates its potential to be used in photovoltaics. Our investigation will be beneficial for researchers to develop less toxic and efficient perovskite materials for the fabrication of optoelectronic devices.

A Rational design of Dithieno-Benzo-Dithiophene based acceptors for organic solar cells

Here, a series of Acceptor–Donor–Acceptor (A–D–A) type compounds are designed. We have theoretically investigated their structural, electronic, optical and photovoltaic properties by employing density functional theory (DFT) formalism. In this regard we have taken Dithieno[2,3−d;2/,3/−d/]benzo[1,2−b;4,5−b/]dithiophene (DTBDT) as donor unit and fused benzothiadiazole along with thiophene (spacer) and cyanoacrylic acid (CAA) (as anchoring group) as acceptor unit. We have investigated different structural and optoelectronic properties viz. dihedral angle, inter-ring bond length, bond length alternation parameters, HOMO-LUMO gap, ionization potential, electron affinity, partial density of states, reorganization energies for holes and electrons, charge transfer rate for holes and electrons, optical absorption and photovoltaic performances of all the designed molecules. Observed reorganization energy and charge transfer rate indicates the electron transporting nature of all the studied molecules. Calculated absorption properties reveal that compounds substituted with different heterocyclic rings in the donor part exhibits the higher value of absorption maximum in the visible range of electromagnetic spectrum. However, the lower values of exciton binding energy and negative Gibb’s free energy change of all the designed molecules indicate the facile charge separation at the donor/acceptor interface. Moreover, the observed photovoltaic properties indicate that all the studied compounds has potential to become candidate for application in photovoltaics. Observed theoretical power conversion efficiency (PCE) reveal that TTPy having maximum PCE of 18.44% will be the best candidate for photovoltaic applications.

Computational investigation of inverse perovskite SbPX3 (X = Mg, Ca, and Sr) structured materials with applicability in green energy resources

With the exchange of ionic positions, antiperovskites (inverse perovskites) have maintained the perovskite crystal structure. Inverse perovskites offer interesting photovoltaic applications as they have a low band gap, strong absorption, and low cost. To confirm the stability, we have calculated some stability parameters firstly, such as structural, elastic, and thermodynamic parameters. The proposed materials are highly stable. We further calculated its optoelectronic and thermoelectric characteristics to substantiate its potential uses in green energy. All of these characteristics are determined using the Density Functional Theory simulation tool WIEN2k. We have utilized Spectroscopic Limited Maximum Efficiency (SLME) to test the theoretical power conversion efficiency of the proposed materials. Eventually, it is clear that these materials are extremely stable and have substantial absorption in the VIS, UV, and NIR bands, which is a commendable attribute gained by a variety of optoelectronic devices. The proposed antiperovskite SbPMg3 with SLME 15.8%, is expected to be a stable yet efficient photovoltaic absorber material. Since the figure of merit of the suggested materials approaches unity, they can also be employed in thermoelectric generators.

Cs2TiI6 (Cs2TiIxBr6-x) Halide Perovskite Solar Cell and Its Point Defect Analysis.

This work presents a comprehensive numerical study for designing a lead-free, all-inorganic, and high-performance solar cell based on Cs2TiI6 halide perovskite with all-inorganic carrier transport layers. A rigorous ab initio density-functional theory (DFT) calculation is performed to identify the electronic and optical properties of Cs2TiI6 and, upon extraction of the existing experimental data of the material, the cell is designed and optimized to the degree of practical feasibility. Consequently, a theoretical power conversion efficiency (PCE) of 21.17% is reported with inorganic TiO2 and CuI as carrier transport layers. The calculated absorption coefficient of Cs2TiI6 reveals its enormous potential as an alternative low-bandgap material for different solar cell applications. Furthermore, the role of different point defects and the corresponding defect densities on cell performance are investigated. It is found that the possible point defects in Cs2TiI6 can form both the shallow and deep defect states, with deep defect states having a prominent effect on cell performance. For both defect states, the cell performance deteriorates significantly as the defect density increases, which signifies the importance of high-quality material processing for the success of Cs2TiI6-based perovskite solar cell technology.

Performance Optimization of Inorganic Cs2TiBr6 Based Perovskite Solar Cell via Numerical Simulation

Perovskite solar cells (PSCs) are considered highly efficient and hold great potential for next‐generation photovoltaic devices due to their excellent properties. However, there are some challenges that hinder their mass production, such as toxicity in lead‐based PSCs, nonstability, and high manufacturing costs. This study aims to address these challenges by proposing a device modeling approach to optimize the design of highly efficient lead‐free cesium titanium bromide (Cs2TiBr6) perovskite solar cells. Cs2TiBr6‐based perovskite solar cells have low performance due to the lack of suitable electron and hole transport layers. Therefore, this study utilizes numerical simulations in SCAPS‐1D to investigate the effect of different parameters, including the doping density of optimized hole and electron transport layers, the thickness of the absorber layer, the NA/ND of the absorption layer, and the defect concentration. The study models six different device structures with different hole transport layerss. However, an optimized novel structure device Se/CuSbS2/Cs2TiBr6/IZGO/FTO/Glass has been proposed, with a theoretical power conversion efficiency of 29.19%. This device has a VOC of 1.33 V, JSC of 24.28 mA cm−2, and FF of 90.46%. Overall, this study demonstrates the potential of Cs2TiBr6 as a promising material for perovskite solar cells, providing a nontoxic, green renewable energy solution for the future.

Collaborative interfacial modification and surficial passivation for high-efficiency MA-free wide-bandgap perovskite solar cells

The wide-bandgap (WBG) perovskite solar cells (PSCs) are the pivotal component for the tandem solar cells, which provides a potential for exceeding the theoretical power conversion efficiency (PCE) limit of the single-junction solar cells. However, the improvement of PCE for perovskite/silicon tandem solar cells is restricted by the interfacial transport barrier loss and the nonradiative recombination loss of the WBG-PSC top cell. Herein, we applied methylammonium-free (MA-free) WBG perovskite for achieving an excellent stability light absorber. This work offers a simultaneous interfacial modification and surficial passivation strategy for suppressing the losses of interfacial barrier and recombination. The mixture of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) and [2-(3,6-dimeth oxy-9H-carbazol-9-yl)ethyl]phosphonic acid (Meo-2PACz) as a self-assembled monolayer (SAM) is employed to facilitate the carrier transport from the perovskite to the anode. 4-trifluoromethyl-phenylammonium iodine (CF3PhAI) is introduced to passivate the surface defect of perovskites. Therefore, the open circuit voltage and PCE of the WBG-PSC are significantly increased. The opaque and transparent electrode (TE) PSCs achieve PCEs of 20.11% and 17.80%, respectively, and the unencapsulated opaque PSC retains more than 85% of the initial efficiency after 1750 h in N2-glovebox. The four-terminal tandem solar cell with perovskite and silicon absorbers was fabricated and obtained 26.59% efficiency. This work provides a simple way to improve the PCE and stability of WBG-PSCs, facilitating the development of tandem solar cells.

Density functional theory study of structural, electronic, optical, mechanical, and thermodynamic properties of halide double perovskites Cs2AgBiX6 (X = Cl, Br, I) for photovoltaic applications

In recent years, double perovskite materials have been considered potential candidates for different applications. Therefore, in this study, we investigated the structural, electronic, optical, and mechanical properties of Cs2AgBiX6 (X = Cl, Br, I) double perovskite materials based on first-principles calculations. All properties were evaluated using the LDA + U technique in the CASTEP code. According to the values of the octahedral factor and tolerance factor, Cs2AgBiX6 (X = Cl, Br, I) possesses a cubic structure with the space group Fm3m (225). The lattice constants were evaluated as 7.7579 Å, 8.1264 Å, and 8.6814 Å for Cs2AgBiCl6, Cs2AgBiBr6, and Cs2AgBiI6, respectively. The tolerance factor and octahedral factor confirmed their structural stability. The electronic properties indicate that the double perovskite materials are semiconductors. The energy band gaps were calculated as 2.02 eV, 1.53 eV, and 1.00 eV for Cs2AgBiCl6, Cs2AgBiBr6, and Cs2AgBiI6, respectively. The optical properties of Cs2AgBiX6 (X = Cl, Br, I) were calculated and discussed in the photon energy range of 0–25 eV to explain the interaction between light and matter. Assessment of the mechanical properties showed that the materials are ductile in nature. The theoretical power conversion efficiencies were calculated as 21.74%, 30.95%, and 30.03% for Cs2AgBiCl6, Cs2AgBiBr6, and Cs2AgBiI6, respectively. Our analysis of the electronic and optical properties demonstrates that these double perovskite materials are suitable for photovoltaic and optoelectronics applications.