In this work, the effects of the metal cations and halide anions on the performance of thylammonium-based perovskite solar cells (PSCs) were investigated. For this purpose, hole transfer material (HTM) and EABX⁠3 (EA=ethylammonium, B=Pb, Sn, Ge, X=Cl, Br, I) perovskite structures were considered from the theoretical viewpoint. Time-dependent density functional theory (TD-DFT) and natural bond orbital (NBO) analysis were applied. The molecular orbitals energy alignment of the materials involved in these PSCs as well as the negative values of Gibbs energies of the electron injection (ΔG⁠inj.) at the EABX⁠3/TiO⁠2 interface and hole transfer (ΔG⁠reg.) at the EABX⁠3/HTM interface show that the studied structures can guarantee the basic photovoltaic processes in this type of solar cells. Based on the results, the coupling constant of EABX⁠3/TiO⁠2 (|V⁠RP|) is the most important parameter that affects the photovoltaic properties of the PSCs and an increase in the size of the halides elevates the electron driving force (eV⁠OC) and decreases |V⁠RP|. A different behavior for the electron transfer rate constant (k⁠inj.) against to the dynamic parameters of eV⁠OC and exciton binding energy (EBE) of the photosensitizers was found. Moreover, the perovskites having a higher electric dipole moment (r⁠k,k?) are able to harvest the incident photon and show a stronger dependence of the light harvesting efficiency (LHE) to r⁠k,k?. Finally, on the basis of the analyses of LHE and the incident photon to current conversion efficiency (IPCE), EAGeCl⁠3 was proposed as a more efficient compound to be used in the PSCs.

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