A Theoretical Evaluation of the Efficiencies of Metal-Free 1,3,4-Oxadiazole Dye-Sensitized Solar Cells: Insights from Electron–Hole Separation Distance Analysis

Abstract

Herein, some novel metal-free 1,3,4-oxadiazole compounds O1–O7 were evaluated for their photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to determine if they can serve as metal-free organic dyes in the use of dye-sensitized solar cells (DSSCs). To understand the trends in the relative efficiencies of the investigated compounds as dyes in DSSCs, their electron contributions, hole contributions, and electron–hole overlaps for each respective atom and fragment within the molecule were analyzed with a particular focus on the electron densities on the anchoring segments. As transition density matrices (TDM) provide details about the departure of each electron from its corresponding hole during excitations, which results in charge transfer (CT), the charge separation distance (Δr) between the electron and its corresponding hole was studied, in addition to the degree of electron–hole overlap (Λ). The latter, single-point excitation energy of each electron, the percentage electron contribution to the anchoring segments of each compound, the incident-photon-conversion-efficiency (IPCE), charge recombination, light harvesting efficiency (LHE), electron injection (Φinj), and charge collection efficiency (ncollect) were then compared to Δr to determine whether the expected relationships hold. Moreover, parameters such as diffusion constant (Dπ) and electron lifetime (t), amongst others, were also used to describe electron excitation processes. Since IPCE is the key parameter in determining the efficiency, O3 was found to be the best dye due to its highest value.

Synthesis, characterization, biological evaluation, DFT and molecular docking studies of (Z)-2-((2-bromo-4-chlorophenyl)imino)methyl)-4-chlorophenol and its Co(ii), Ni(ii), Cu(ii), and Zn(ii) complexes

“…92 A study by Bulat et al , debunked previous studies that suggested that an electron that occupies the HOMO level will automatically be excited to the LUMO level as this study revealed that an electron's position in atomic space and the contour of the molecule also play a role in excitations. 93 Nevertheless, it is still widely accepted that HOMO–LUMO energy gaps play a significant role in electron excitations. 94 Comparing the ligand to the complexes, we observe greater stability, larger IP, lower EA, larger η , lower δ and ω indices in the former.…”

Molecular engineering of inorganic halide perovskites and HTMs for photovoltaic applications

“…The perovskite regeneration process is related to Gibbs energy change of the hole transport from the perovskite to the HTM and can be expressed by Equation () [45]. …”