ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Impact of a twisted conformation in an indoleninyl-thiobarbiturate sensitizer on dye-sensitized solar cell performance

Abdul Qaiyum Ramle, Enis Nadia Md Yusof, M. H. Buraidah, Shameer Hisham, Wan Jefrey Basirun, Edward R. T. Tiekink, and M. F. Aziz

School of Chemical Sciences, Universiti Sains Malaysia, Gelugor, Malaysia

E-mail: qaiyum@usm.my

Received: 31 October 2025  Accepted: 13 March 2026

Abstract:

A new zwitterionic dye incorporating an indolenine core functionalized with thiobarbiturate was successfully synthesized in 45% yield. The molecular structure was confirmed by NMR, FT-IR, and HRMS analyses. Photophysical studies revealed two prominent absorption bands in the range 300 to 500 nm in up to 2.07 × 10⁴ M^− 1 cm^− 1. These peaks correspond to the π-π* transition and intramolecular charge transfer (ICT), respectively. Notably, both absorption peaks exhibited distinct hypsochromic and hyperchromic shifts in response to increasing solvent polarity. Electrochemical analysis indicated the HOMO (‒5.37 eV) and LUMO (‒2.96 eV) energy levels are well-aligned with the conduction band of TiO₂ and the redox potential of the I^‒/I₃^‒ electrolyte, fulfilling the requirements for a dye-sensitized solar cells (DSSC) sensitizer. DFT calculations provide valuable insights into the electronic structure and support the experimental energy levels. The fabricated device achieved a maximum efficiency of 0.33% under a light intensity of 30 mW/cm². The low photocurrent efficiency is attributed to restricted π-conjugation and inefficient charge transfer resulting from the twisted molecular geometry. This work highlights the potential of small organic molecule dyes as photosensitizers for DSSC applications.

Graphical abstract

Keywords: Indolenine dye; Thiobarbiturate; Photophysical attributes; DFT; Electrochemistry; DSSC

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04813-6

Chemical Papers 80 (6) 7019–7028 (2026)