Performance Analysis of Perovskite Solar Cells Using DFT-Extracted Parameters of Metal-Doped TiO2 Electron Transport Layer

The performance of perovskite solar cells (PSCs) depends heavily on the electronic and optical properties of the electron transport layer (ETL). Density functional theory (DFT) uses a quantum-mechanical approach to accurately predict the properties of different layers in PSCs, including the ETL. Titanium dioxide (TiO2) is a widely used material for the ETL in PSCs. In this work, we use first-principles calculations based on DFT to obtain the electronic and optical properties of pristine rutile TiO2 and TiO2 doped with tin (Sn) and zinc (Zn). DFT-extracted carrier mobility, band gap, and the absorption spectrum of TiO2 are used in the SCAPS-1D device simulator to evaluate the performance of the solar cell device, with respect to dopant concentration and thickness of TiO2. PSCs with 3.125 mol % Sn-doped TiO2 achieve a maximum power conversion efficiency (PCE) of 17.14 versus 13.70% with undoped TiO2. We have also compared the performance of PSCs with Sn-doped and Zn-doped TiO2. For the same dopant concentration, Sn-doped TiO2 offers 0.63% higher PCE than the Zn-doped counterpart. The results are in good agreement with reported experimental findings and provide a reliable means of evaluating PSC performance by combining first-principles (DFT) calculations with conventional device simulations

Performance Analysis of Perovskite Solar Cells Using Dft-Extracted Parameters of Metal-Doped Tio2 Electron Transport Layer

The performance of perovskite solar cells (PSCs) depends heavily on the electronic and optical properties of the electron transport layer (ETL). Density functional theory (DFT) uses a quantum-mechanical approach to accurately predict the properties of different layers in PSCs, including the ETL. Titanium dioxide (TiO2) is a widely used material for the ETL in PSCs. In this work, we use first-principles calculations based on DFT to obtain the electronic and optical properties of pristine rutile TiO2 and TiO2 doped with tin (Sn) and zinc (Zn). DFT-extracted carrier mobility, band gap, and the absorption spectrum of TiO2 are used in the SCAPS-1D device simulator to evaluate the performance of the solar cell device, with respect to dopant concentration and thickness of TiO2. PSCs with 3.125 mol % Sn-doped TiO2 achieve a maximum power conversion efficiency (PCE) of 17.14 versus 13.70% with undoped TiO2. We have also compared the performance of PSCs with Sn-doped and Zn-doped TiO2. For the same dopant concentration, Sn-doped TiO2 offers 0.63% higher PCE than the Zn-doped counterpart. The results are in good agreement with reported experimental findings and provide a reliable means of evaluating PSC performance by combining first-principles (DFT) calculations with conventional device simulations

Investigation of Cssn0.5ge0.5i3-On-Si Tandem Solar Device Utilizing SCAPS Simulation

With the perovskite-on-Si tandem solar technology at the onset of commercialization, it becomes imperative to tackle the toxicity concern of Pb in the perovskite structure. This study utilizes solar cell capacitance simulator (SCAPS) simulation software to investigate a tandem device with the crystalline Si (c-Si; bandgap: 1.12 eV) bottom cell in a mechanically stacked configuration with the stable and nontoxic CsSn0.55Ge0.55I3 (bandgap: 1.5 eV) as the top cell active layer. The device performance has been compared against that of a traditional tandem solar device setup utilizing MAPbI3 (bandgap: 1.55 eV) as the top cell active layer. Simulation results reveal power conversion efficiency (PCE) values of standalone CsSn0.55Ge0.55I3, MAPbI3, and c-Si cells to be 7.45%, 20.01%, and 25.95%, respectively, all in good agreement with published experimental results. The current matching condition between the top perovskite cell and the bottom c-Si cell has been probed through variation of perovskite layer thickness, yielding optimized thickness values for CsSn0.55Ge0.55I3 and,,,MAPbI3 to be 365 and 225 nm, respectively. A tandem device with CsSn0.55Ge0.55I3-on-Si showcases a PCE of 28.53% (Voc: 1.72 V; Jsc: 20.02 mA/cm²; and FF: 83.74%) compared with an MAPbI3-on-Si device yielding a PCE of 32.29% (Voc: 1.88 V; Jsc: 19.969 mA/cm²; and FF: 85.99%). The results and analyses of this study highlight the feasibility of utilizing nontoxic materials, such as CsSn0.55Ge0.55I3, to attain high tandem device PCE values

Simulation Studies to Quantify the Impacts of Point Defects: an Investigation of Cs2agbibr6 Perovskite Solar Devices Utilizing Zno and Cu2o As the Charge Transport Layers

In this investigation, we have applied SCAPS and wxAMPS to simulate defects and probe a photovoltaic device utilizing Cs2AgBiBr6 as the active photovoltaic layer and ZnO and Cu2O as the electron transport layer (ETL) and hole transport layer (HTL) respectively. At the Cs2AgBiBr6 bulk we find that with increasing defect density, each defect level has increasing impact on all device performance parameters. At a given defect density however, we find that that deeper defects have more profound impacts on Jsc and FF, and minimal effects on Voc. Specific to the Cs2AgBiBr6 structure, we have investigated VAg (shallow defect), VBi (deep defect) and Bri (quasi-deep defect). Our results provide insight into the growth conditions of Cs2AgBiBr6, with a need to have both Br-poor and Bi-rich conditions, and a preference for the latter over the former to suppress the deeper defect. Exploring the performance kinetics at the ZnO/Cs2AgBiBr6 and Cs2AgBiBr6/Cu2O interfaces due to defect type, location and density, we showcase a remarkably stable behavior in both Voc and Jsc across both interfaces. We attribute this to much higher charge mobilities in the ZnO and Cu2O compared to the Cs2AgBiBr6 layer combined with similar defect densities across the layers, leading to effective charge extraction and minimal charge recombination

Exploring Solar Cell Performance of Inorganic Cs2tibr6 Halide Double Perovskite: A Numerical Study

With a high power-conversion efficiency (PCE) of over 23%, perovskite solar cell (PSC) technology holds a viable trajectory for commercialization. Despite its attractive features, the use of lead and degradable components in the device need to be addressed. To this end, we have carried out simulation studies to explore a non-toxic and inorganic device utilizing Cs2TiBr6 as the active layer and Cu2O as the hole transport layer (HTL). We have investigated a few of the most critical areas of device physics to glean insights into possible ways of improving the performance of such a viable technology. A PCE of 14.68% (open-circuit voltage Voc of 1.10 V, short-circuit current Jsc of 25.82 mA/cm2, and fill factor FF of 51.74%) was obtained at an optimal perovskite layer thickness of 800 nm. Our investigation further reveals that with increasing perovskite thickness, as J0 (saturation current) decreases, Voc increases. By varying the radiative recombination rate, we quantitatively demonstrate an inverse relationship with PCE, and report out a PCE of 20.49% at a 100X lower than usual recombination rate. A PCE of 14.68% was obtained with an optimal work function of 5.1 eV for the metal back contact. A conduction band offset of −0.1 eV between the TiO2 electron transport layer (ETL) and the active layer and a valence band offset of −0.4 eV between the active layer and the HTL produce optimal PCE values of 14.68% and 18.97% respectively. Lastly, we demonstrate that Cs2TiBr6 is more sensitive to defect density than the device HTL and ETL by a factor of 10

Combined experimental and first principles look into (Ce, Mo) doped BiVO4

Here we investigated the effects of Ce and Mo doping on hydrothermally synthesized bismuth vanadate BiVO4 nanoparticles (NPs). The existence of monoclinic scheelite and tetragonal zircon phases of NPs was validated from Rietveld refinement of the powdered X-ray diffraction, room temperature Raman, and Fourier-transform infrared spectroscopy. The co-doping of Bi and V sites with respective Ce and Mo dopants in a mixed tetragonal zircon and monoclinic scheelite phases of BiVO4 lattice was corroborated from high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The photoluminescence measurements revealed enhancement of photo-generated carrier recombination in (Ce, Mo) co-doped BiVO4 NPs which may have hampered its photocatalytic efficiency in degrading the methylene blue dye. The simulations based on Hubbard U corrected density functional theory (DFT+U) suggest that Mo and Ce co-doping introduced deep impurity states which may have facilitated the photo-generated carrier recombination detrimental to photocatalytic performance. The UV-vis diffuse reflectance measurements provided evidence for the presence of these defect states. In summary, this work may have presented a comprehensive experimental analysis of (Ce, Mo) doped BiVO4 supported by DFT simulations

Unconventional Rapid Synthesis of Layered Manganese Dioxide Nanostructures for Selective Oxidation of 5‑Hydroxymethylfurfural to 2,5-Diformylfuran

Nanostructured first row transition metal (Mn, Fe, Co, Ni, and Cu) oxides (TMOs) have shown promise as catalysts for creation of new and ransformative technologies for manufacturing value-added chemicals that are energy- and atom-efficient. Most of the synthesis routes to TMOs involve harsh reaction conditions or prolonged preparation times. Herein, we use potassium superoxide (KO2), a commercially available stable salt of superoxide, as a viable oxidant for rapid but mild redox synthesis of birnessite type layered manganese dioxide (δ-MnO2) nanomaterials. These δ-MnO2 materials are synthesized in a fast (as fast as 5 min), ambient (room temperature), and convenient condition, employing a simple laboratory apparatus (grinding with mortar and pestle followed by washing with water). Characterization studies reveal a hierarchical porosity and sponge-like morphology for the δ-MnO2 nanomaterial, whereas the surface area of the material is tunable as a function of the adopted synthetic aspects. The δ-MnO2 materials deliver promising catalytic activity in the selective aerobic oxidation of 5-hydroxymethylfurfural alcohol (HMF) to 3,5-diformylfuran (DFF), an important probe reaction to transform biomass-derived feedstocks to useful chemicals. Density functional theory (DFT) is used to investigate the interaction of HMF with the catalyst surface and to chart out the energetics pathway of system relaxation, together showcasing various bond dissociations, intermediate steps, and rate limiting kinetics

Exploring solar cell performance of inorganic Cs2TiBr6 halide double perovskite: A numerical study

With a high power-conversion efficiency (PCE) of over 23%, perovskite solar cell (PSC) technology holds a viable trajectory for commercialization. Despite its attractive features, the use of lead and degradable components in the device need to be addressed. To this end, we have carried out simulation studies to explore a non-toxic and inorganic device utilizing Cs2TiBr6 as the active layer and Cu2O as the hole transport layer (HTL). We have investigated a few of the most critical areas of device physics to glean insights into possible ways of improving the performance of such a viable technology. A PCE of 14.68% (open-circuit voltage Voc of 1.10 V, short-circuit current Jsc of 25.82 mA/cm2, and fill factor FF of 51.74%) was obtained at an optimal perovskite layer thickness of 800 nm. Our investigation further reveals that with increasing perovskite thickness, as J0 (saturation current) decreases, Voc increases. By varying the radiative recombination rate, we quantitatively demonstrate an inverse relationship with PCE, and report out a PCE of 20.49% at a 100X lower than usual recombination rate. A PCE of 14.68% was obtained with an optimal work function of 5.1 eV for the metal back contact. A conduction band offset of −0.1 eV between the TiO2 electron transport layer (ETL) and the active layer and a valence band offset of −0.4 eV between the active layer and the HTL produce optimal PCE values of 14.68% and 18.97% respectively. Lastly, we demonstrate that Cs2TiBr6 is more sensitive to defect density than the device HTL and ETL by a factor of 10