TiO₂ Photoelectrode Band Gap Modification Using Carbon Quantum Dots (CQDs) for Dye-Sensitised Solar Cells (DSSCs)

Abstract:

In this study, a CQDs at different concentration is used to modify the TiO₂ photoelectrode band gap which can improve light absorption of DSSC. The photoelectrode is immersed in different CQDs concentration at 2.5, 5.0, 7.5 and 10 mg/ml to study the effect on TiO₂. It was found that photoelectrode with 7.5 mg/ml CQDs was successfully narrowing the TiO₂ band gap and generated the highest photocurrent and power conversion efficiency at 17.06 mA/cm² and 7.23% respectively, compared to pristine TiO₂ (PT) at 10.94 mA/cm² and 4.63% . The band gap narrowing mechanism for CQDs- TiO₂ is obtained from the Tauc’s plot method using absorption spectra. The result shows a pristine TiO₂ photoelectrode (PT) band gap is 3.38 eV, upon existing of CQDs, the band gap of all photoelectrodes with CQDs at 2.5, 5.0, 7.5 and 10 were reduced to 3.30 eV, 3.28 eV, 3.09 eV, and 3.29 eV respectively. PG 7.5 cell with lowest band gap at 3.09 eV generates effective electron transport from N719 dye to CQDs/ TiO₂ layer compared to other photoelectrodes. The band gap narrowing effect is attributed from chemical bonds of Ti-O-C molecules between CQDs/TiO_2. Thus, extra energy states are introduced between CQDs and TiO_2. The location of these energy will present a quantum confinement effect which narrow the CQDs-TiO₂ band gap which extend the light absorption to visible region.

• Periodical: Key Engineering Materials (Volume 908)
• Pages: 265-270
• DOI: https://doi.org/10.4028/p-577y33
• Online since: January 2022
• Authors: Noor Fadzilah Mohamed Sharif*, Suhaidi Shafie, Mohd Zainal Abidin Ab Kadir, Muhamad Faiz Md Din, Yusnita Yusuf, S. Shaban
• Keywords: Bandgap Narrowing, Carbon Quantum Dots (CQDs), Quantum Confinement Effect, TiO₂- CQDs Photoelectrode

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