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

Louis-Charl Cloete Coetzee, Adedapo Sunday Adeyinka and Nomampondo Magwa
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Louis-Charl Cloete Coetzee: Department of Chemistry, University of South Africa, Private Bag X6, Florida, Roodepoort, Johannesburg 1710, Gauteng, South Africa
Adedapo Sunday Adeyinka: Research Centre for Synthesis and Catalysis, Department of Chemical Sciences, University of Johannesburg, Auckland Park, Johannesburg 2006, Gauteng, South Africa
Nomampondo Magwa: Department of Chemistry, University of South Africa, Private Bag X6, Florida, Roodepoort, Johannesburg 1710, Gauteng, South Africa

Energies, 2022, vol. 15, issue 13, 1-23

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 (Δ r ) 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 ( Φ inj ), and charge collection efficiency ( n collect ) were then compared to Δ r to determine whether the expected relationships hold. Moreover, parameters such as diffusion constant ( D π ) 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.

Keywords: DFT; TD-DFT; DSSCs; donor; ?-spacer; acceptor (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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