Solar Cell Devices Research Articles

Synthesis and Processing Strategy for High-Bandgap PbS Quantum Dots: A Promising Candidate for Harvesting High-Energy Photons in Solar Cells.

The wide tunability of the energy bandgap of colloidal lead sulfide (PbS) quantum dots (QDs) has uniquely positioned them for the development of single junction and tandem solar cells. While there have been substantial advancements in moderate and narrow bandgap PbS QDs-ideal for single junction solar cells and the bottom cell in tandem solar cells, respectively; progress has been limited in high-bandgap PbS QDs that are ideally suited for the formation of the top cell in tandem solar cells. The development of appropriate high bandgap PbS QDs would be a major advancement toward realizing efficient all-QD tandem solar cells utilizing different sizes of PbS QDs. Here, we report a comprehensive approach encompassing synthetic strategy, ligand engineering, and hole transport layer (HTL) modification to implement high-bandgap PbS QDs into solar cell devices. We achieved a greater degree of size homogeneity in high-bandgap PbS QDs through the use of a growth retarding agent and a partial passivation strategy. By adjusting the ligand polarity, we successfully grow HTL over the QD film to fabricate solar cells. With the aid of an interface modifying layer, we incorporated an organic HTL for the realization of high-performance solar cells. These solar cells exhibited an impressive open-circuit voltage of 0.824 V and a power conversion efficiency of 10.7%, marking a 360% improvement over previous results.

(Sm3+/Eu3+/Tm3+)-TiO2 heterostructures for electrochemical and photovoltaic applications

This study reports on the synthesis of lanthanide oxides triply doped titania, forming a novel hetero-system known as (Sm3+/Eu3+/Tm3+)-TiO2. An environmentally friendly sol gel method was used to synthesize the energy-efficient (Sm3+/Eu3+/Tm3+)-TiO2, and thin films were deposited by spin coating. Electrode and solar cell devices were fabricated under ambient conditions, and rare earth doping enhanced the opto-electronic aspects of the host by narrowing the band gap up to 3.92, 3.85, and 3.56 eV. Particle sizes for the pure and doped materials were 85.15 and 82.72 nm, respectively. With a specific capacitance of 667.34 F g−1, the lanthanide-doped ornamented nickel foam electrode outperformed the pristine electrode, which had a specific capacitance of 169.59 F g−1. Moreover, this electrode exhibited tiny equivalent series resistance (Rs) of 0.13 Ω, indicating quicker response kinetics at the interface, in addition to its electrical double layer capacitance behavior. Electrochemical studies revealed that (Sm3+/Eu3+/Tm3+)-TiO2 semiconductor has a high specific power density of 8157.03 W kg−1, compared to 4079.73 W kg−1 for undoped titania. This improved specific power density demonstrates its suitability for practical scale applications. The produced materials were an excellent HER electro-catalyst with remarkably lower overpotential and Tafel slopes i.e., of 137 mV and 87.6 mV dec−1, in a respective manner, in comparison to the reference TiO2 with 147 mV and 104.5 mV dec−1, respectively. The electro-catalyst's response to the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was enhanced upon lanthanide doping. Additionally, this substance successfully retrieved electrons from a perovskite solar cell device, achieving efficiency levels of 16.49 and 16.75 % in both forward and reverse bias with fill factor increase.

Tuning of Optoelectronic Characteristics of Quinoxalineimide-based Novel Non-Fullerene Acceptors for Organic Photovoltaic Applications

Organic solar cells (OSCs) have made remarkable progress due to developing novel materials and device architectures. Herein, we designed six new non-fullerene acceptors (QM1–QM6) having a quinoxalineimide (QI) as the central-building-block. We aimed to explore the potential of QI-containing structures for developing high-performance acceptors for OSCs. These designed molecules possess a fusion of the QI unit with a thienylthiophene backbone and are equipped with various efficient end-capping groups. Extensive theoretical calculations were carried out to evaluate the structural and charge distribution characteristics, including the optical, optoelectronics, density of states, transition density matrix, molecular electrostatic potential (ESP), reorganization energies, and photovoltaic properties. The results revealed that the designed series exhibited improved electron–hole pair coherences, efficient charge transportation, and favorable ESP patterns, suggesting their suitability for enhanced optical and electronic characteristics. Furthermore, the hole and electron overlap analyses demonstrated significant overlap in QM1–QM6, indicating efficient charge transfer and higher charge mobilities. Additionally, the analysis of reorganization energies showed low reorganization energy values, indicating favorable charge mobility rates and potential for high-efficiency solar cell devices. This research establishes a strong foundation for utilizing QI-containing fused units as central building blocks for designing high-performance acceptors, opening up new avenues for advancements in OSCs technology.

Stable WSeTe/PtTe2 van der Waals heterojunction: Excellent mechanical, electronic, and optical properties and device applications

Janus WSeTe and PtTe2 monolayers have attracted much attention due to their outstanding electronic properties. To explore their combined advantages and to find new physics, we construct WSeTe/PtTe2 vdW heterojunctions and use the most stable configurations A4 and B1 to explore their various physical properties and device applications. It is found that both A4 and B1 hold exceptional mechanical properties. They are type-II semiconductors, and types of band alignment and band gap size can be tuned flexibly by external electric field and vertical strain. Based on such a property, we design a strain-controlled high on–off-ratio mechanical switching device. They also show an excellent light response and high photoelectric power conversion efficiency (PCE), which can be tuned greatly by the external electric field and vertical strain as well. For example, light adsorption in visible and infrared region can be improved greatly by the compressive strain. Particularly, we find for B1 in the intrinsic state or with a small tensile strain of 0.3 Å, or for A4 with small electric field of −0.3 V/Å, they all hold type-II band alignment and have very high PCE and large visible light absorption, based on these results, we propose high-performance solar cell devices.

Ecodesign of Kesterite Nanoparticles for Thin Film Photovoltaics at Laboratory Scale.

This manuscript investigates the efficient synthesis of copper zinc tin sulfide (CZTS) nanoparticles for CZTS thin film solar cell applications with a primary focus on environmental sustainability. Underpinning the investigation is an initial life-cycle assessment (LCA) analysis. This LCA analysis is conducted to evaluate the environmental impact of different synthesis volumes, providing crucial insights into the sustainability of the synthesis process by considering the flows of material and energy associated with the process. Life-cycle assessment results demonstrate that significant reductions to the environmental impact can be made by increasing the synthesis volume of CZTS nanoparticle ink. Using a 5-fold increase in volume can reduce all 11 investigated environmental impacts by up to 35.6%, six of these impacts demonstrating reductions >10% and the amount of global warming potential is reduced by 21.4%. Motivated by the LCA results, COMSOL simulations are employed to understand the fluid flow patterns in large-scale fabrication. Various sizes and speeds of stirrer bars are investigated in these simulations, and it is determined that a 50 mm stir bar at 200 rpm represents the optimal configuration for the synthesis process in a 500 mL flask. Subsequently, large-batch CZTS nanoparticle inks are synthesized using these parameters and compared to small-batch samples. The light absorbers are characterized using Raman spectroscopy and X-ray diffraction, confirming favorable properties with close-to-ideal elemental ratios in large-batch synthesis. Finally, solar cell devices fabricated utilizing CZTSSe absorbers from the large volume synthesis process demonstrate comparable performance to those fabricated using small-batch synthesis, with uniform power conversion efficiencies of around 5% across the substrate. This study highlights the potential of large-volume CZTS nanoparticle synthesis for efficient and environmentally friendly CZTS solar cell fabrication, contributing to the advancement of sustainable renewable energy technologies.

Designing and simulating of new highly efficient ultra-thin CIGS solar cell device structure: Plan to minimize cost per watt price

This research paper examines the execution of ultra-thin solar cells made from chalcopyrite copper indium gallium diselenide (CIGS). The study presents a new CIGS heterojunction solar cell structure, which includes a Cd-free tungsten disulfide (WS2) buffer layer and poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) passivation layer. The performance of the solar cell is raised by a back surface field (BSF). A highly recombining rear surface is kept away from minority carriers by a field created by further strong doping at the back. The structure is Ni/PEDOT:PSS/CIGS/WS2/ZnO/Al and has been estimated numerically using the Opto-electrical stimulation of semiconductor layers simulator SCAPS-1D. A high efficiency with a Back surface passivated layer of 25.70 % with Voc of 0.81 V, Jsc of 39.33 mA/cm2, and FF of 79.89 % and without passivated layer efficiency of 17.58 % with Voc of 0.73 V, Jsc of 32.18 mA/cm2, and FF of 74.78 % is found for the intended CIGS-based solar cell with WS2 buffer. The interface between CIGS and WS2 forms a band structure that resembles spikes. This structure is crucial in enhancing the outputs by reducing carrier recombination. The optimal thicknesses for the buffer and CIGS absorber layers are 0.02 μm and 0.2 μm, respectively. These findings help reduce the cost per watt of the solar cell. Fabrication at a mass production scale, minimizing the thickness will have a significant impact on reducing cost.

Factors influencing charge transport at perovskite–charge transport layer interfaces: current strategies, challenges, and perspectives based on first-principles studies

Charge transport at the interface between a perovskite absorbing layer and the charge transport layer (CTL) has a major role in determining perovskite solar cell device efficiency and long-term stability. Hence, a detailed operando characterization of the factors influencing charge transport at perovskite/CTL interfaces needs to be discussed. This perspective summarizes recent studies involving charge transport through perovskite and CTL interfaces. An overview is provided of the recent advances in the fundamental understanding of how these interfaces influence device performance. Based on recently reported articles, some of the crucial factors such as energy-level alignment, defects, and non-radiative recombination are identified. The identification is made from an atomistic point of view as these factors have a strong influence on charge transport at perovskite/CTL interfaces. Furthermore, we share our perspective on calculating said factors influencing interfacial charge transport from different approaches using density functional theory (DFT) and beyond.

Advances and challenges in molecular engineering of 2D/3D perovskite heterostructures.

Organic-inorganic hybrid perovskites have been intensively studied in past decades due to their outstanding performance in solar cells and other optoelectronic devices. Recently, the emergence of two-dimensional/three-dimensional (2D/3D) heterojunctions have enabled many solar cell devices with >25% power conversion efficiency, driven by advances in our understanding of the structural and photophysical properties of the heterojunctions and our ability to control these properties through organic cation configuration in 2D perovskites. In this feature article, we discuss a fundamental understanding of structural characteristics and the carrier dynamics in the 2D/3D heterojunctions and their impact factors. We further elaborate the design strategies for the molecular configuration of organic cations to achieve thorough management of these properties. Finally, recent advances in 2D/3D heterostructures in solar cells, light-emitting devices and photodetectors are highlighted, which translate fundamental understandings to device applications and also reveal the remaining challenges in ligand design for the next generation of stable devices. Future development prospects and related challenges are also provided, with wide perspectives and insightful thoughts.

Innovative surface passivation of CZTSSe thin films: Ammonium sulfide treatment with plasma etching

For CZTS(e) solar cells, the passivation of interfacial defects is crucial for effectively reducing carrier recombination at the interface. This study examined the combined impact of plasma etching and surface sulfuration on the passivation of interface defects in CZTSSe thin films. The results indicated that plasma etching could improve the surface quality of the thin films and passivate surface defects. The (NH4)2S vapor had a significant sulfuration effect on the surface of the CZTSSe thin films post-etching. The surface defects of the CZTSSe film were passivated by the sulfur element entering the film by sulfuration. Moreover, the bandgap of the CZTSSe thin films was improved. The efficiency of the solar cell device increased by 1.72 % with a plasma etching duration of 5 min and (NH4)2S vaporization treatment of 15 min. This study proposes a novel approach that employs surface passivation techniques to enhance the efficiency of CZTSSe thin film solar cells.

Recent advances in transition metal dichalcogenides-based materials for fourth-generation perovskite solar cell devices

Recent advances in transition metal dichalcogenides-based materials for fourth-generation perovskite solar cell devices

Enhancement of Quantum Efficiency in Perovskite Solar Cells Through Whispering Gallery Modes from Titanium Oxide Micro‐Resonators

With the aid of 3D full‐field finite difference time–domain simulations, model configurations for thin‐film solar cell devices that include periodically arranged microspheres, exhibiting resonating whispering gallery modes (WGMs), are proposed. The microspheres present, either immersed in perovskite or coated with perovskite layer, between the electron‐ and hole‐transport layers show enhanced current‐conversion efficiency. The presence of WGMs lead to enhancement in the absorption of layer. The incoming electromagnetic wave couples with microsphere and forms confined resonating modes. Different designs are examined for deciding the appropriate position of WGM exhibiting spheres with respect to thin‐film perovskite solar cell (PSC) featuring back reflector and optimized antireflectance coating. Since the incoupling element is lossless, energy stored in microspheres is absorbed efficiently by the underlying active material. This directly contributes to the increment in the current density of the solar cell. Thus, the devices show a higher current density of 23.62 mA cm−1, while that in planar solar cell device shows current density of 13.68 mA cm−1, for the same thickness of perovskite layer. This leads to more than 70% enhancement in the short‐circuit current density than the conventional PSCs device of similar size.

Impact of nanoscale Cu (I) precursors prepared by solution process on large-area CdTe solar cells

In recent years, the study of Cu (Ӏ) precursors in high-performance CdTe thin-film solar cell devices has received increasing attention. However, few studies have been reported on nanoscale Cu (I) precursors in large-area CdTe devices (≥1 cm2). Here, three different Cu (Ӏ) nano precursors have been rapidly prepared by solution method (CuCl ethanol solution, CuI acetonitrile solution, and CuSCN aqueous ammonia solution) and their effects on the performance of commercial large-area CdTe thin-film solar cells have been investigated. The results show that the distribution amount and uniformity of the nano precursor particles on the CdTe back surface have a large impact on the device performance. The CuCl nanoparticles are more uniformly distributed and the device performance is more excellent. CuI nanoparticles easily formed clusters at grain boundaries. Denser distribution of CuSCN nanoparticles. The thermal diffusion conditions (temperature, time and precursor concentration) have a significant effect on the device performance, but the most reasonable thermal diffusion conditions tend to be the same for all devices. This suggests that the thermal diffusion conditions are determined by the nature of the CdTe absorber layer itself and are not interfered by different nano precursors.

Enhancing the stability of DSSC by Co-activation of microwave synthesized TiO2 with biomass derived carbon dots

Dye-sensitized solar cells (DSSCs) that utilize natural dyes have garnered interest due to their low cost, eco-friendly manufacturing process, and competitive photovoltaic performance. However, their efficiency and stability issues have hindered their widespread implementation. To enhance their performance, this paper proposes a novel approach of modifying the photoanode with carbon dots (CDs) to align the band gap for easier carrier collection. The material properties were thoroughly characterized by examining their structural, morphological, optical, and electrical properties. In this study, titanium dioxide (TiO2) was synthesized using the microwave-assisted solvothermal method, while nitrogen-doped CDs derived from Citrus medica fruit juice were prepared using a simple hydrothermal treatment. Three sets of Natural Dye Sensitized Solar Cells (NDSSC) devices were created using co-activated photoanode (CD/TiO2) and unmodified photoanode (TiO2) with Platisol T/sp coated ITO serving as the counter electrode. Hibiscus (Hibiscus rosa-sinensis) and Onion (Allium cepa) peel extracts were utilized as sensitizers and Iodolyte HI-30 as the electrolyte. The most efficient device attained an efficiency of 3.5 % with Voc = 0.81 V and Jsc = 6.57 mA/cm2. This marks the highest efficiency reported using Hibiscus as a sensitizer with the current configuration, accompanied by prolonged device stability. This study showcases the potential of Citrus medica-derived nitrogen-doped CDs in achieving durable device stability.

A Dual‐Functional Molecule for Efficient and Stable CsPbI3‐Based 2D Dion–Jacobson Perovskite Solar Cells

Herein, a new type of CsPbI3‐based 2D Dion–Jacobson (DJ) perovskites is reported, featuring a general formula of (PDMA)Csn−1PbnI3n+1 (n = 1, 2, 3, 4) with 1,4‐phenylenedimethanammonium (PDMA) as the organic spacer cation. The crystal structure, optical and electric properties, and surface morphology of the perovskite films are fully surveyed. The solar cell device based on the n = 4 film delivers a champion power conversion efficiency (PCE) of 11.27%, further improved to 12.61% by treating with the PDMA molecules. The PDMA passivation suppresses non‐radiative recombination, extends charge‐carrier lifetime, and reduces open‐circuit voltage loss. A gradient energy level near the film surface facilitates electron extraction, alleviating charge accumulation. The PDMA molecules form a protective layer, inhibiting water infiltration and enhancing stability. The optimized device exhibits excellent shelf stability with no PCE decay after 110 days. In this study, a dual‐functional molecule is introduced as a new DJ‐type spacer and an effective passivation agent for efficient and stable CsPbI3‐based 2D perovskite solar cells.

Tunnel oxide thickness-dependent dominant carrier transport in crystalline silicon solar cells

Silver consumption reduction is a current development in commercial tunnel passivated contact (TOPCon) crystalline silicon solar cell devices aimed at lowering the entire production cost of photovoltaic energy sources. It depends on the number of fingers and/or finger spacing (SP) on a cell area. In this paper, we analyze the possibility of minimizing silver use with respect to the dominant carrier transport mechanism. The carrier transporting mechanism, such as “pinhole” and/or “tunnel” models, is identified by examining temperature-dependent I–V characteristics of polysilicon passivating contact as a function of tunnel oxide (TO) thickness from 0.6 to 2.2 nm. Thermal oxidation was used to produce ultrathin TO films (0.6–2.2 nm) with temperature and gas ratio controlled. We find that the “pinholes” transport mechanism prevails when the TO thickness exceeds 1.6 nm, whereas the “tunnel” mode dominates when the TO thickness is less than 1.4 nm. The pinhole density is critical in pinhole mode for increasing SP. It is found that low pinhole densities and thick TO thickness (more than 1.6 nm) are two of the primary causes of narrow SP in TOPCon devices, which need a considerable quantity of silver. The experimental TOPCon devices as a function of TO thickness show a considerable trade-off between open circuit voltage (Voc) and fill factor (FF). While Voc rises, FF drops as TO thickness increases. The mechanism is described.

Facile synthesis and characterization of PbS thin films doped with various aluminum concentrations for photovoltaic applications

In this study, aluminum doped lead sulfide (PbS:Al) thin films were deposited on soda lime glass substrates using chemical bath deposition (CBD) technique. The structural, morphological, optical and electrical properties of as-deposited PbS thin films were studied as a function of Al concentration (0, 2, 4, 6, 8 at. %). The deposited films can be analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), UV-Vis-NIR spectroscopy and Hall measurement. From SEM, it was evident that the thickness of the films decreased from 750 nm (0 at. %) to 280 nm (8 at. %) with increased Al concentration. XRD analysis revealed that the prepared films exhibited face centered cubic structure without any other binary phases. The average crystallite size of the films decreased from 33.71 to 20.45 nm. The direct optical band gap values were increased from 0.90 to 1.29 eV. The optical parameters such as refractive index (n), extinction coefficient (k), real (ɛ 1) and imaginary (ɛ 2) parts of the dielectric constant were 1.51–2.04, 0.0035–0.0075, 2.50–6.20 and 0.005–0.16 respectively. The absorption coefficient (α) of all the deposited films was in the range of ≈105 cm−1. The electrical resistivity of the deposited films was found in the range of 102–103 Ω·cm. The overall analysis indicate that the deposited PbS:Al thin film shows promise as an absorbing layer for heterojunction solar cell devices.

Reactive DC Sputtered TiO2 Electron Transport Layers for Cadmium‐Free Sb2Se3 Solar Cells

AbstractThe evolution of Sb2Se3 heterojunction devices away from CdS electron transport layers (ETL) to wide bandgap metal oxide alternatives is a critical target in the development of this emerging photovoltaic material. Metal oxide ETL/Sb2Se3 device performance has historically been limited by relatively low fill factors, despite offering clear advantages with regards to photocurrent collection. In this study, TiO2 ETLs are fabricated via direct current reactive sputtering and tested in complete Sb2Se3 devices. A strong correlation between TiO2 ETL processing conditions and the Sb2Se3 solar cell device response under forward bias conditions is observed and optimized. Numerical device models support experimental evidence of a spike‐like conduction band offset, which can be mediated, provided a sufficiently high conductivity and low interfacial defect density can be achieved in the TiO2 ETL. Ultimately, a SnO2:F/TiO2/Sb2Se3/P3HT/Au device with the reactively sputtered TiO2 ETL delivers an 8.12% power conversion efficiency (η), the highest TiO2/Sb2Se3 device reported to‐date. This is achieved by a substantial reduction in series resistance, driven by improved crystallinity of the reactively sputtered anatase‐TiO2 ETL, whilst maintaining almost maximum current collection for this device architecture.

Unveiling the potential of graphene and S-doped graphene nanostructures for toxic gas sensing and solar sensitizer cell devices: insights from DFT calculations.

In this work, we explore the potential of 2D materials, particularly graphene and its derivatives, for eco-friendly electricity generation and air pollution reduction. Leveraging the significant surface area of graphene nanomaterials, the susceptibility of these graphene-based nanostructures to hazardous substances and their applicability in clean solar cell (SSC) devices were systematically investigated using density functional theory (DFT), as implemented within Gaussian 5.0 code. Time-dependent DFT (TD-DFT) was employed to characterize the UV-visible spectrum of unstrained nanostructures. Herein, we considered three potentially harmful gases-CO, NH3, and Br2. Adsorption calculations revealed a notable interaction between the pure graphene nanostructure and Br2 gas, while the S-doped counterpart exhibited reduced interaction. Saturated S-doped nanostructures demonstrated an enhanced affinity for NH3 and CO gases compared to their pure S-doped counterparts, attributed to the sulfur (S) atom facilitating gas molecule binding to the nanostructure's surface. Furthermore, simulations of the SSC device architecture indicated the superior performance of the pure graphene nanostructure in terms of light-harvesting efficiency, injection energy, and electron injection into the lower conduction band of CBM titanium dioxide (TiO2). These findings suggest a potential avenue for developing nanostructures tailored for SSC devices and gas sensors, offering a dual solution to address air pollution concerns. Density function theory was used to compute the ground and excited state properties for pure and sulfur-doped graphene nanostructures. The hybrid function B3LYP with a 6-31G* basis set was utilized to describe the exchange correlation. Gauss Sum 2.2 software is used to estimate the density of state (DOS) for all structures under investigation.

Strain Heterogeneity and Extended Defects in Halide Perovskite Devices.

Strain is an important property in halide perovskite semiconductors used for optoelectronic applications because of its ability to influence device efficiency and stability. However, descriptions of strain in these materials are generally limited to bulk averages of bare films, which miss important property-determining heterogeneities that occur on the nanoscale and at interfaces in multilayer device stacks. Here, we present three-dimensional nanoscale strain mapping using Bragg coherent diffraction imaging of individual grains in Cs0.1FA0.9Pb(I0.95Br0.05)3 and Cs0.15FA0.85SnI3 (FA = formamidinium) halide perovskite absorbers buried in full solar cell devices. We discover large local strains and striking intragrain and grain-to-grain strain heterogeneity, identifying distinct islands of tensile and compressive strain inside grains. Additionally, we directly image dislocations with surprising regularity in Cs0.15FA0.85SnI3 grains and find evidence for dislocation-induced antiphase boundary formation. Our results shine a rare light on the nanoscale strains in these materials in their technologically relevant device setting.

Synergetic Triple Absorber Based High‐Efficiency Solar Cell Design

AbstractComputational analysis of triple absorber‐based solar cell structure is undertaken. This solar cell device configuration allows better utilization of the incident solar spectrum. Three different absorbers with a band gap in the range 1–1.5 eV are sandwiched between high‐doped p+ and n+ regions in descending order of electron affinity to form an energy‐matched multiple absorber device. A comprehensive analysis of key device parameters influencing performance, including band gap, conduction band alignment, interfacial defects, and thickness, is presented. The optimized triple absorber device shows beyond Shockley–Queisser limit (SQ limit) performance under the constraint of passivated interfaces with defect density below 1013 cm−2. Wide spectrum coverage leads to high short circuit current and an efficiency of 40.3%, which is higher than the SQ limit for single band gap solar cell.