Improving Hole Densities and Minority Carrier Lifetimes of Cadmium Telluride Solar Cells

The objective of this thesis is to address two of the main components that affect the VOC of polycrystalline cadmium telluride (CdTe) thin-film solar cells, namely improving the carrier lifetime and carrier concentration (doping). In order to reduce carrier recombination and increase carrier lifetimes in the device, strategies with and without Cl and Se are developed, to reduce and passivate the inherent recombination centers (grain boundaries, interfaces, intra-grain defects) in polycrystalline CdTe devices. Grain sizes in the order of 1 mm are achieved and mechanisms driving lifetimes exceeding 1 µs are discussed. Moreover, hole concentrations that are orders of magnitude higher than the standard 1014 cm-3 values (seen for traditional Cu doping), are achieved with Group-V dopants like P, As, and Sb. In the future, non-Cl methods would need to be developed not only for dopant activation but defect passivation and grain growth to overcome current material and device limitations