  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.
