Dr. Ajith Thomas
Research
My research focuses on advancing the performance and scalability of next-generation solar cell technologies through material innovation, device engineering, and interface optimization. I explore organic and hybrid photovoltaic systems using nanomaterials such as quantum dots, conjugated polymers, and tailored interfacial layers. My work bridges fundamental materials science with real-world energy applications, aiming to improve efficiency, stability, and cost-effectiveness.
Keywords
Quantum dot solar cells, hybrid photovoltaics, bulk heterojunctions, ligand exchange, interface engineering, device architecture, CdSe, PbS, P3HT, nanomaterials, spin coating, QDSSCs, inverted solar cells.
Key Areas of Research
1. Quantum Dot-Enhanced Hybrid Solar Cells
One of my primary research directions involves replacing traditional fullerene derivatives like PCBM with semiconductor quantum dots to improve light absorption and charge dynamics. In a notable study, I introduced a CdSe QD-based interfacial buffer layer in an inverted P3HT:CdSe bulk heterojunction (BHJ) solar cell. This innovation led to a record open-circuit voltage of 0.96 V for this material system by effectively reducing interface recombination. By forming a quantum junction using differently passivated QDs, I further improved charge extraction and device efficiency.
2. Inverted Architectures with Engineered Interfaces
I developed an inverted ZnO/P3HT:PbS hybrid solar cell where the introduction of a CdSe QD buffer layer between the ZnO and the active layer significantly enhanced performance. This interface engineering optimized charge extraction and minimized recombination, boosting efficiency from 1.7% to 2.4%.
3. Ligand Chemistry for Quantum Dot Devices
Efficient charge transport in QD-based solar cells depends heavily on surface chemistry. I proposed a hybrid solid-state ligand exchange strategy combining TBAI and EDT for PbS QD solar cells. This synergistic approach achieved improved packing and passivation, leading to a power conversion efficiency of 8.2%, one of the best for this class of devices.
In a related study, I optimized post-synthesis purification and ligand exchange processes, ensuring complete iodide exchange in thicker QD films. This simplification in device fabrication yielded reproducible efficiencies up to 5.55% while maintaining high-quality surface passivation and minimized trap states.
4. Solvent Engineering for Organic Solar Cells
I also explored how solvent polarity affects active layer morphology in organic BHJ solar cells. By incorporating trace amounts of nitrobenzene into chlorobenzene, I demonstrated improved P3HT domain ordering and interfacial area, which enhanced device performance. However, I also identified the detrimental effects of excessive polarity, providing valuable insights into solvent optimization.
5. Quantum Dot-Sensitized Solar Cells (QDSSCs)
My research extends to sensitized solar cells using type-II CdSe–Cu₂Se core–shell quantum dots, synthesized via high-temperature organometallic routes. When integrated with a ZnS-passivated TiO₂ photoanode and sulfide/polysulfide electrolyte system, these devices achieved up to 4.83% efficiency. This work highlights the potential of band-aligned heterostructures and interfacial engineering in enhancing QD-based solar energy conversion.
I have conducted my research in collaboration with esteemed institutions including the Indian Institute of Science (IISc), Bangalore, Cochin University of Science and Technology (CUSAT), Kerala, Mahatma Gandhi University, Kottayam, and St. Thomas College, Palai, Kerala, India.