Work

Sterically Controlled Interfacial Charge‐Transfer Mechanisms in Unsymmetrical Squaraine Dyes for Suppressed Aggregation and Enhanced Performance in High‐Efficiency Dye‐Sensitized Solar Cells

Year: 2026

Type: article

Abstract: Steric regulation at the dye/semiconductor interface critically governs charge recombination and interfacial energetics in dye‐sensitized solar cells (DSSCs) but remains poorly defined for unsymmetrical squaraine sensitizers. Here, two π‐extended unsymmetrical squaraine dyes (AQ1 and AQ2) are designed to clarify how alkyl‐chain‐induced steric modulation influences aggregation, surface packing, and intramolecular charge‐transfer (ICT) dynamics. Both dyes show strong visible–near‐infrared absorption and suitable the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO) alignment for electron injection into TiO 2 . In AQ2, branched alkyl substituents provide enhanced steric shielding at the TiO 2 interface, suppressing aggregation, modifying interfacial dipoles, and increasing R rec . Importantly, efficiency gains arise mainly from steric control of interfacial energetics and recombination kinetics rather than aggregation suppression alone. Consequently, AQ2‐based DSSCs deliver 7.41% power conversion efficiency with higher R rec = 11.64 Ω and longer electron lifetime ( τ = 8.58 ms) than AQ1, despite lower dye loading. Electrochemical impedance spectroscopy (EIS) and density functional theory (DFT) corroborate suppressed back‐electron transfer.

Source: ChemistryOpen

DOI: 10.1002/open.70199

Authors: Abdullah N. Alotaibi, Sultan A. Al‐horaibi, Yaaser Q. Almulaiky, Ali Arabie

Institutions: Imam Mohammad ibn Saud Islamic University, Albaydha University, University of Jeddah

Language: English

Topic: TiO2 Photocatalysis and Solar Cells

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

SDG: Affordable and clean energy

Open Access status: gold

Estimated APC paid: $2,790