"2D-Transition Metal Dichalcogenides (TMDCs) for High-Efficiency Thin-Film CdTe Solar Cells" 

Karthika Haridas, MSE PhD Candidate 

Advisor: Professor Shubhra Bansal

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ABSTRACT

Cadmium telluride (CdTe) has long stood as a mature and commercially successful thin-film photovoltaic technology due to its near-optimal bandgap (~1.45 eV), high absorption coefficient (~105 cm-1), compatibility with large-area manufacturing, and low-cost production. However, despite recent advances that have increased efficiencies to 23.1 %, CdTe solar cells are still limited by an open-circuit voltage (VOC) deficit of over 400 mV compared to their radiative limit. This loss mainly comes from non-radiative recombination at the back contact, caused by Fermi-level pinning and interface defect states. Traditional methods, such as CdSeTe alloying, Cu-based doping, and ZnTe:Cu back contacts, have provided small improvements but still face issues with chemical stability and limited control over band alignment. Recent developments in two-dimensional (2D) transition metal dichalcogenides (TMDCs), like MoS2 solar cells, open new possibilities for interface engineering in CdTe devices. Due to their tunable electronic structures, high carrier mobility, and van der Waals (vdW) bonding, TMDCs can form atomically sharp, lattice-mismatch-free heterojunctions that facilitate carrier extraction. This review covers the progress of CdTe solar cell efficiencies, the main cause of the VOC deficit, and extensive efforts in material modification, doping, and tandem integration to address these challenges. Additionally, it will also discuss the emergence, properties, and photovoltaic applications of TMDCs