Effect of various electron and hole transport layers on the performance of CsPbI3-based perovskite solar cells: A numerical investigation in DFT, SCAPS-1D, and wxAMPS frameworks (2211.02968v1)

Abstract: CsPbI3 has recently received tremendous attention as a possible absorber of perovskite solar cells (PSCs). However, CsPbI3-based PSCs have yet to achieve the high performance of the hybrid PSCs. In this work, we performed a density functional theory (DFT) study using the Cambridge Serial Total Energy Package (CASTEP) code for the cubic CsPbI3 absorber to compare and evaluate its structural, electronic, and optical properties. The calculated electronic band gap (Eg) using the GGA-PBE approach of CASTEP was 1.483 eV for this CsPbI3 absorber. Moreover, the computed density of states (DOS) exhibited the dominant contribution from the Pb-5d orbital, and most charge also accumulated for the Pb atom as seen from the electronic charge density map. Fermi surface calculation showed multiband character, and optical properties were computed to investigate the optical response of CsPbI3. Furthermore, we used IGZO, SnO2, WS2, CeO2, PCBM, TiO2, ZnO, and C60 as the electron transport layers (ETLs), and Cu2O, CuSCN, CuSbS2, Spiro-MeOTAD, V2O5, CBTS, CFTS, P3HT, PEDOT: PSS, NiO, CuO, and CuI as the hole transport layers (HTLs) to identify the best HTL/CsPbI3/ETL combinations using the SCAPS-1D solar cell simulation software. Among 96 device structures, the best-optimized device structure, ITO/TiO2/CsPbI3/CBTS/Au was identified, which exhibited an efficiency of 17.9%. The effect of absorber and ETL thickness, series resistance, shunt resistance, and operating temperature was also evaluated for the six best devices along with their corresponding generation rate, recombination rate, capacitance-voltage, current density-voltage, and quantum efficiency characteristics. The obtained results from SCAPS-1D were also compared with wxAMPS simulation software.

• The paper reveals that the optimal ITO/TiO2/CsPbI3/CBTS/Au configuration achieves a PCE of 17.9%, marking a significant performance improvement.
• The paper employs DFT to uncover CsPbI3's structural and electronic properties, determining a 1.483 eV bandgap and highlighting the critical role of Pb-5d orbitals.
• The paper cross-validates SCAPS-1D and wxAMPS simulations to provide actionable insights for device optimization and guide future experimental research in perovskite solar cells.

Insights into the CsPbI₃-Based Perovskite Solar Cells: Numerical Investigations with DFT, SCAPS-1D, and wxAMPS Frameworks

Perovskite solar cells (PSCs) are at the forefront of photovoltaic research due to their potential for high efficiency and low-cost fabrication. The present paper focuses on CsPbI₃-based PSCs, which have been shown to offer improved thermal stability compared to hybrid perovskites, albeit with challenges in achieving competitive power conversion efficiencies (PCEs). This research employs Density Functional Theory (DFT), SCAPS-1D, and wxAMPS simulations to explore and optimize the structural, electronic, and optical properties of CsPbI₃, alongside various electron and hole transport layers (ETLs and HTLs).

Computational Evaluations of CsPbI₃

The paper begins with a fundamental investigation of CsPbI₃ using DFT to elucidate its structural and electronic characteristics. The calculated electronic bandgap (Eg) is 1.483 eV, slightly lower than previously reported values, attributed to the GGA-PBE potential typically underestimating semiconductor bandgaps. The density of states (DOS) analysis highlights the significant role of the Pb-5d orbital in electronic properties, substantiating the material's n-type behavior. The Fermi surface topology further underscores CsPbI₃'s multiband character, crucial for its functionality in PSCs.

Optimization of ETL/HTL Combinations

A pivotal aspect of the paper is the search for optimal ETL/HTL configurations to maximize PCE. Utilizing the SCAPS-1D simulator, 96 potential device structures were examined, yielding the best structure in ITO/TiO₂/CsPbI₃/CBTS/Au, achieving a PCE of 17.9%. This surpasses previous simulations, marking a notable improvement. The paper underscores the significance of effective band alignment at ETL/HTL interfaces, with TiO₂, ZnO, and WS₂ showing superior photovoltaic parameters.

Device Performance Analysis

The paper provides an extensive examination of how device parameters influence CsPbI₃-based PSC performance. Notably, both the thicknesses of absorber and ETL, as well as series and shunt resistances, are shown to significantly affect device metrics such as Voc, Jsc, FF, and overall PCE. The intricate interactions revealed by the simulations contribute to the understanding of charge transport and recombination dynamics in these devices.

Comparison with wxAMPS and Prior Work

The paper aligns its SCAPS-1D findings with those from wxAMPS simulations, bolstering the credibility of the results with cross-validation. The comparative analysis accentuates the accuracy of these simulations, portraying SCAPS-1D as a reliable tool for solar cell performance prediction. Furthermore, the paper contrasts its findings with prior experimental and theoretical work, demonstrating that the simulation approach provides a valuable predictive model, particularly due to the constraints of experimental exploration.

Implications and Future Directions

The implications of this research are twofold: practically, it guides the experimental fabrication of CsPbI₃-based PSCs towards optimized configurations; theoretically, it enriches the understanding of perovskite material properties and device physics. Potential future developments could include the integration of machine learning techniques to expedite the discovery of efficient material combinations. Additionally, expanding the paper to other perovskite compositions and device architectures may unlock further efficiency improvements.

In conclusion, the paper offers a comprehensive evaluation of CsPbI₃-based PSCs through advanced numerical approaches, pushing the boundaries towards higher PCEs. Such research is pivotal in the ongoing quest to develop sustainable and cost-effective solar energy solutions.