Optical and structural engineering of CH3NH3PbI3 film via CB-antisolvent for efficient and stable perovskite solar cells

Herein, we investigated details in the effect of using chlorobenzene (CB) antisolvent on the structural and optical properties of CH₃NH₃PbI₃ perovskite films such as surface roughness, crystallite size, lattice constants, micro-strain, dislocation density, direct and indirect optical bandgap, refractive index, extinction coefficient, dielectric constant, optical conductivity, and Urbach energy (Eu) for achieving efficient and stable perovskite solar cells (PSCs). The RMS roughnesses of the perovskite films with and without CB were 8.32 and 150.63 nm, respectively. The use of CB during the deposition process of CH₃NH₃PbI₃ film caused the shrinkage of the perovskite lattice and the size of the crystallite was larger than the sample without CB (56. 99 nm and 44.99 nm for samples with and without CB, respectively). The direct optical band-gap for samples with and without CB was 1.61 and 1.51 eV, respectively, and their indirect band-gap was 1.54 and 1.45 eV, respectively. The difference between the direct and indirect optical band gap for both samples was 60 meV (Rashba splitting effect). Eu values for perovskite films with and without CB were 0.04 and 0.22 eV, respectively. The efficiency of PSCs with and without CB was ~ 14% and ~ 6%, respectively. The solar cell related to the sample with and without CB maintained 84 and 18% of its initial efficiency after 60 days, respectively (environmental conditions: 40% RH and 30 ˚C). This comparative study of the structural and optical properties of the perovskite film provides the basis for future enhancements to the efficiency and stability of PSCs.