Understanding Auger recombination in perovskite solar cells

Dynamic tuning of optoelectronic and mechanical properties in TlMCl3 (M = Ge, Sn) under pressure-induced phase transition

Recent advances in lead-free halide perovskites have expanded their potential use in solar panels and optoelectronic applications. Motivated by their excellent properties, we investigate the physical characteristics of two lead-free halide perovskites, TlMCl3 (M = Ge, Sn), under hydrostatic pressure. This paper explores the pressure-induced semiconductor-to-metal phase transition in halide perovskites TlMCl3 (M = Ge, Sn), focusing on their optoelectronic and mechanical properties. Using density functional theory (DFT), the study investigates structural, electronic, optical, and mechanical changes under hydrostatic pressures up to 6.5 GPa. Both TlGeCl3 and TlSnCl3 maintain a cubic perovskite structure, but exhibit decreasing lattice parameters and unit cell volumes with increased pressure. Electronic analyses reveal a transition from semiconducting to metallic states for both materials under pressure: TlGeCl3's band gap collapses to 0 eV at 6 GPa and TlSnCl3 at 6.5 GPa according to TB-mbj, with GGA-PBE predicting transitions at 5 GPa for TlGeCl3 and 3 GPa for TlSnCl3. This transition is confirmed through partial density of states (PDOS) and band structure calculations. The SOC effect reduces the bandgap in TlMCl3 (M = Ge, Sn), boosting their optoelectronic application potential. Enhanced dielectric constants and refractive indices under pressure improve their efficiency in solar cells and LEDs by reducing carrier recombination and strengthening photon-electron interactions. Their high transparency, UV reflectivity, and increased absorption and conductivity under pressure make them suitable for UV coatings, optical filters, and advanced optoelectronic devices. Mechanical analyses show improved stiffness and ductility, with TlSnCl3 demonstrating excellent machinability. The pressure-enhanced ductility of TlMCl3 (M = Ge, Sn) makes it suitable for flexible electronics, wearable devices, and robust solar cells. Furthermore, their outstanding photovoltaic potential is driven by large optical absorption and high charge carrier mobility, aided by their small effective masses.

Investigation of novel all-inorganic perovskites Ba3PX3 (X = F, Cl, Br, I) with efficiency above 29

Lead-free inorganic halide perovskites, specifically Ba3PX3 (X = Cl, F, I, Br) have gained attention in green photovoltaics due to their remarkable mechanical, optical, structural, and electronic properties. Using first-principles calculations, we investigated the mechanical, electronic, and optical characteristics of Ba3PX3, revealing direct band gaps at the Γ-symmetry point, assessed with the PBE and HSE functionals. The charge distribution analysis shows strong ionic bonding between Ba and halides and covalent bonding between P and halides. The perovskites exhibit desirable optical properties, including high absorption in the visible-UV range, making them ideal for optoelectronic devices. Furthermore, SCAPS-1D simulations on Ba3PF3, Ba3PCl3, Ba3PBr3, and Ba3PI3-based solar cells with the SnS2 ETL layer revealed power conversion efficiencies of 23.15%, 16.13%, 21.63%, and 29.89%, respectively. Consequently, the Ba3PI3 compound shows significant potential as an absorber in solar cells based on the SnS2 ETL layer in the near future.

Achieving efficiency above 30% with new inorganic cubic perovskites X2SnBr6 (X = Cs, Rb, K, Na) via DFT and SCAPS-1D

The solar sector is shifting towards lead-free, inorganic cubic halide perovskites due to their superior structural, electronic, and optoelectronic properties. This study uses density functional theory (DFT) to examine the structural, electronic, and optical properties of X2SnBr6 (X = Cs, Rb, K, Na) and assesses their photovoltaic performance through the Solar Cell Capacitance Simulator - One Dimensional (SCAPS-1D). The results show each material has a direct band gap at the Γ-point, low optical losses, and high absorption, making them promising for solar and optoelectronic applications. For Cs2SnBr6, Rb2SnBr6, K2SnBr6, and Na2SnBr6 absorbers with TiO2 electron transport layer (ETL), power conversion efficiencies (PCE) of 29.22%, 27.25%, 30.62%, and 29.51% were achieved, with open-circuit voltages (VOC) of 1.02, 0.87, 0.83, and 0.77 V, short-circuit currents (JSC) of 32.27, 36.72, 42.69, and 45.48 mA cm-2, and fill factors (FF) of 88.38, 85.18, 85.96, and 81.85%, respectively. Variations in X-cation size notably influence bandgap energy, band structure, and optoelectronic properties, impacting solar cell efficiency. This study supports the development of lead-free hybrid solar cells and other optoelectronic devices.

Boosting Efficiency in Carbon Nanotube-Integrated Perovskite Photovoltaics

Carbon nanomaterials (graphene, carbon nanotubes, and graphene oxide) have potential applications for optoelectronics, thanks to their superior electronic and optical characteristics. The remarkable stability of carbon-based perovskite solar cells (PSCs) has attracted significant attention. Herein, a fluorine-doped carbon nanotube (F-CNT) is incorporated into the PSCs as a hole-transporting layer (HTL) in between methylammonium lead iodide (MAPbI3) and the rear electrode to develop an effective MAPbI3/HTL interface. The F-CNT bridges both the MAPbI3 film and the Au electrode and promotes photocarrier extraction and transportation between the two layers. The article presents a simulation-driven optimization approach for the development of efficient CNT-based PSCs. Many factors, such as the total defect density of the perovskite, the shallow acceptor density of the F-CNTs film thickness, the perovskite thickness, parasitic resistances, and temperature, have been studied using SCAPS-1D simulations. Utilizing the photovoltaic software SCAPS-1D, we simulated defect states and interfaces to approximate a realistic perovskite device in our analyses. The CNT-based PSC with an architecture of FTO/TiO2/MAPbI3/F-CNTs/Au achieved an outstanding power conversion efficiency (PCE) of 26.91%, with a fill factor (FF) of 84.23%.

Modelling and Numerical Evaluation of Photovoltaic Parameters of a Highly Efficient Perovskite Solar Cell Based on Methylammonium Tin Iodide

Designing a high-performance solar cell structure requires the understanding of material innovation, device engineering, charge behavior, operation characteristics and efficient photoconversion of light to generate electricity. This study offers a detailed numerical evaluation of the device physics in a highly efficient methylammonium-based perovskite solar cell (PSC) of the configuration, FTO/WO3/CH₃NH₃SnI₃/GO/Fe. Utilizing the SCAPS-1D device simulator, an impressive open-circuit voltage (Voc) of 1.3184 V, short-circuit current density (Jsc) of 35.10 mA/cm2, Fill factor (FF) of 78.38 %, and power conversion efficiency (PCE) of 36.24 % were achieved. The model cell exhibits a robust photon capture of 100 % quantum efficiency between 360 and 750 nm. The study also presents a temperature-dependent band alignment diagram which posted a built-in potential (Vbi) of 0.62 eV. The Vbi at 400 K was found to be 0.58 eV indicating that the model cell exhibits a decent temperature tolerance, and can retain approximately 93 % of its power at 400 K. Through Mott-Schottky capacitance analysis, deeper insights into the space-charge region are inferred, while recombination-generation investigations emphasize the significance of electronic properties in optimizing device performance. This paper, therefore, lays the foundation for future studies, offering clear pathways for device optimization and identifying key areas that require further investigation.

Effects of adjusting nickel pulse count on NiOx films prepared by atomic layer deposition

The paper describes the preparation of NiOx films using atomic layer deposition (ALD) and analyzes their hole transport properties. During the ALD process, NiOx films with varying properties were fabricated by adjusting the number of nickel pulses in the reaction. Various characterization techniques were employed to investigate the morphology, composition, optical, and electrical properties of the films prepared with different numbers of nickel pulses. The study reveals that as the number of Ni pulses increases, the content of Ni metal and Ni(OH)2 in the NiOx films changes, and post-annealing treatment can significantly enhance the performance of the NiOx films. Finally, NiOx was used as a hole transport layer to successfully fabricate silicon solar cells, resulting in an increase in power conversion efficiency (PCE) from 17.89% to 18.89% compared to untreated cells.

Design and Simulation for Minimizing Non-Radiative Recombination Losses in CsGeI2Br Perovskite Solar Cells

CsGeI2Br-based perovskites, with their favorable band gap and high absorption coefficient, are promising candidates for the development of efficient lead-free perovskite solar cells (PSCs). However, bulk and interfacial carrier non-radiative recombination losses hinder the further improvement of power conversion efficiency and stability in PSCs. To overcome this challenge, the photovoltaic potential of the device is unlocked by optimizing the optical and electronic parameters through rigorous numerical simulation, which include tuning perovskite thickness, bulk defect density, and series and shunt resistance. Additionally, to make the simulation data as realistic as possible, recombination processes, such as Auger recombination, must be considered. In this simulation, when the Auger capture coefficient is increased to 10-29 cm6 s-1, the efficiency drops from 31.62% (without taking Auger recombination into account) to 29.10%. Since Auger recombination is unavoidable in experiments, carrier losses due to Auger recombination should be included in the analysis of the efficiency limit to avoid significantly overestimating the simulated device performance. Therefore, this paper provides valuable insights for designing realistic and efficient lead-free PSCs.

Experimental and computational DFT, drift-diffusion studies of cobalt-based hybrid perovskite crystals as absorbers in perovskite solar cells

The optimised designs of dimethyl ammonium cobalt formate-based perovskite crystals [(CH3)2NH2]Co(HCOO)3 were experimentally synthesized and computationally utilized as absorbers for perovskite solar cells (PSCs). Crystals were grown using solvothermal synthesis. Additive materials (Fe, Ni) are responsible for the growth and suppression of crystals in the micrometre range. Temperature and pressure were altered to obtain optimum growth conditions. Grown crystals were characterized by spectroscopy (XRD, FT-IR, UV-Vis) and optical microscopy. Combined density functional theory (DFT) and drift-diffusion modelling frameworks were simulated. These simulators were used to examine various perovskite absorbers for solar-cell configurations. Field calculations were used to examine the structural stability, band structure, and electronic contribution of the constituent elements in [(CH3)2NH2]Co1-nMn(HCOO)3 (M = Fe, Ni and n = 0, 0.1) as absorber material. Conventional TiO2 and spiro-OMeTAD were used as the electron-transport layer and hole-transport layer, respectively, and Pt was used as a back contact. Comprehensive analysis of the effects of several parameters (layer thickness, series and shunt resistances, temperature, generation-recombination rates, current-voltage density, quantum efficiency) was carried out using simulation. Our proposed strategy may pave the way for further design of new absorber materials for PSCs.

Improved eco-friendly CsSn0.5Ge0.5I3 perovskite photovoltaic efficiency beyond 20% with SMe-TATPyr hole-transporting layer

Perovskites composed of inorganic cesium (Cs) halide provide a route to thermally resistant solar cells. Nevertheless, the use of hole-transporting layers (HTLs) with hydrophobic additives is constrained by moisture-induced phase deterioration. Due to significant electrical loss, dopant-free HTLs are unable to produce practical solar cells. In this article, we designed a two-dimensional 1,3,6,8-tetrakis[5-(N,N-di(p-(methylthio)phenyl)amino-p-phenyl)-thiophen-2-yl]pyrene (termed SMe-TATPyr) molecule as a new HTL to regulate electrical loss in lead-free perovskite solar cells (PSCs). We optimized the power conversion efficiency (PCE) of PSCs based on mixed tin (Sn)/germanium (Ge) halide perovskite (CsSn0.5Ge0.5I3) by exploring different factors, such as the deep and shallow levels of defects, density of states at the valence band (NV), thickness of the perovskite film, p-type doping concentration (NA) of HTL, the series and shunt resistances, and so on. We carried out comparative research by employing the 1D-SCAPS (a solar cell capacitance simulator) analysis tool. Through optimization of the PSC, we obtained the highest parameters in the simulated solar cell structure of fluorine tin oxide (FTO)/titanium dioxide (TiO2)/CsSn0.5Ge0.5I3/SMe-TATPyr/gold (Au), and the PCE reached up to 20% with a fill factor (FF) of 81.89%.

Comparative study of distinct halide composites for highly efficient perovskite solar cells using a SCAPS-1D simulator

This research investigates the influence of halide-based methylammonium-based perovskites as the active absorber layer (PAL) in perovskite solar cells (PSCs). Using SCAPS-1D simulation software, the study optimizes PSC performance by analyzing PAL thickness, temperature, and defect density impact on output parameters. PAL thickness analysis reveals that increasing thickness enhances JSC for MAPbI3 and MAPbI2Br, while that of MAPbBr3 remains steady. VOC remains constant, and FF and PCE vary with thickness. MAPbI2Br exhibits the highest efficiency of 22.05% at 1.2 μm thickness. Temperature impact analysis shows JSC, VOC, FF, and PCE decrease with rising temperature. MAPbI2Br-based PSC achieves the highest efficiency of 22.05% at 300 K. Contour plots demonstrate that optimal PAL thickness for the MAPbI2Br-based PSC is 1.2 μm with a defect density of 1 × 1013 cm-3, resulting in a PCE of approximately 22.05%. Impedance analysis shows the MAPbBr3-based PSC has the highest impedance, followed by Cl2Br-based and I-based perovskite materials. A comparison of QE and J-V characteristics indicates MAPbI2Br offers the best combination of VOC and JSC, resulting in superior efficiency. Overall, this study enhances PSC performance with MAPbI2Br-based devices, achieving an improved power conversion efficiency of 22.05%. These findings contribute to developing more efficient perovskite solar cells using distinct halide-based perovskite materials.

Achieving above 24% efficiency with non-toxic CsSnI3 perovskite solar cells by harnessing the potential of the absorber and charge transport layers

Lead toxicity is a barrier to the widespread commercial manufacture of lead halide perovskites and their use in solar photovoltaic (PV) devices. Eco-friendly lead-free perovskite solar cells (PSCs) have been developed using certain unique non- or low-toxic perovskite materials. In this context, Sn-based perovskites have been identified as promising substitutes for Pb-based perovskites due to their similar characteristics. However, Sn-based perovskites suffer from chemical instability, which affects their performance in PSCs. This study employs theoretical simulations to identify ways to improve the efficiency of Sn-based PSCs. The simulations were conducted using the SCAPS-1D software, and a lead-free, non-toxic, and inorganic perovskite absorber layer (PAL), i.e. CsSnI3 was used in the PSC design. The properties of the hole transport layer (HTL) and electron transport layer (ETL) were tuned to optimize the performance of the device. Apart from this, seven different combinations of HTLs were studied, and the best-performing combination was found to be ITO/PCBM/CsSnI3/CFTS/Se, which achieved a power conversion efficiency (PCE) of 24.73%, an open-circuit voltage (VOC) of 0.872 V, a short-circuit current density (JSC) of 33.99 mA cm-2 and a fill factor (FF) of 83.46%. The second highest PCE of 18.41% was achieved by the ITO/PCBM/CsSnI3/CuSCN/Se structure. In addition to optimizing the structure of the PSC, this study also analyzes the current density-voltage (J-V) along with quantum efficiency (QE), as well as the impact of series resistance, shunt resistance, and working temperature, on PV performance. The results demonstrate the potential of the optimized structure identified in this study to enhance the standard PCE of PSCs. Overall, this study provides important insights into the development of lead-free absorber materials and highlights the potential of using CsSnI3 as the PAL in PSCs. The optimized structure identified in this study can be used as a base for further research to improve the efficiency of Sn-based PSCs.

Harnessing the potential of CsPbBr3-based perovskite solar cells using efficient charge transport materials and global optimization

Perovskite solar cells (PSCs) have become a possible alternative to traditional photovoltaic devices for their high performance, low cost, and ease of fabrication. Here in this study, the SCAPS-1D simulator numerically simulates and optimizes CsPbBr3-based PSCs under the optimum illumination situation. We explore the impact of different back metal contacts (BMCs), including Cu, Ag, Fe, C, Au, W, Pt, Se, Ni, and Pd combined with the TiO2 electron transport layer (ETL) and CFTS hole transport layer (HTL), on the performance of the devices. After optimization, the ITO/TiO2/CsPbBr3/CFTS/Ni structure showed a maximum power conversion efficiency (PCE or η) of 13.86%, with Ni as a more cost-effective alternative to Au. After the optimization of the BMC the rest of the investigation is conducted both with and without HTL mode. We investigate the impact of changing the thickness and the comparison with acceptor and defect densities (with and without HTL) of the CsPbBr3 perovskite absorber layer on the PSC performance. Finally, we optimized the thickness, charge carrier densities, and defect densities of the absorber, ETL, and HTL, along with the interfacial defect densities at HTL/absorber and absorber/ETL interfaces to improve the PCE of the device; and the effect of variation of these parameters is also investigated both with and without HTL connected. The final optimized configuration achieved a VOC of 0.87 V, JSC of 27.57 mA cm-2, FF of 85.93%, and PCE of 20.73%. To further investigate the performance of the optimized device, we explore the impact of the temperature, shunt resistance, series resistance, capacitance, generation rate, recombination rate, Mott-Schottky, JV, and QE features of both with and without HTL connected. The optimized device offers the best thermal stability at a temperature of 300 K. Our study highlights the potential of CsPbBr3-based PSCs and provides valuable insights for their optimization and future development.