Photovoltaic Performance Investigation of Cs₃Bi₂I₉-Based Perovskite Solar Cells with Various Charge Transport Channels Using DFT and SCAPS-1D Frameworks

Cs3Bi2I9 as a solar absorber material is a strong contender for lead-free perovskite solar cells (PSCs). The presence of bismuth (Bi) in Cs3Bi2I9 leads to the origin of interesting optoelectronic properties along with a suitable optical band gap and high absorption coefficient. However, further analysis of the crystal structure, optical, and electronic properties of this material is required for efficient photovoltaic (PV) applications. The potential of Cs3Bi2I9 perovskite as an absorber layer for solar cells (SCs) was first analyzed by performing density functional theory (DFT) calculations to observe its structural, optical, and electronic properties. Band structure reveals an indirect band gap (2.42 eV), and density of states (DOS) data show good conductivity primarily contributed by the 5p and 6s orbital electrons of I and Bi atoms. Strong electronic charge buildup is seen in the electronic charge density map surrounding the I atom, as well as the covalent bonds between the I and Bi atoms. The frequency-dependent dielectric function and absorption calculations reveal that Cs3Bi2I9 might be a potential material in optoelectronic and photovoltaic systems. We also performed numerical simulations using the one-dimensional solar cell capacitance simulator (SCAPS-1D) for 49 different PSC configurations with Cs3Bi2I9 absorber, electron transport layers (ETLs) comprising WS2, indium–gallium–zinc oxide (IGZO), SnO2, ZnO, C60, TiO2, and phenyl-C61-butyric acid methyl ester (PCBM), and hole transport layers (HTLs) like Cu2O, CuSCN, NiO, poly(3-hexylthiophene) (P3HT), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), Spiro-MeOTAD, and CuI. Simulation results reveal that the Cu2O HTL exhibited the best power conversion efficiency (PCE) for all of the ETLs. Of the 49 configurations, the six best configurations with the Cu2O HTL and different ETLs were analyzed to study the effect of absorber and ETL thickness, series and shunt resistances, operating temperature, capacitance, Mott–Schottky, generation, and recombination rate on the PV performance. Current–voltage (J–V) characteristics and quantum efficiency (QE) were computed for all of these configurations to understand the impact of the absorber, ETL, and HTL on the PV parameters. This comprehensive simulation study will assist researchers in the fabrication of cheap and efficient PSCs without lead and open new horizons in the field of solar technology.