Development of a substrate configuration CdTe/CdS solar cell on flexible molybdenum substrate

CdTe is one of the leading thin film photovoltaic materials with an optimum band gap of 1.5 eV for the efficient photo conversion. The development of photovoltaic devices on metallic substrates is interesting due to the flexible nature of the devices. One of the hurdles in the development of CdTe devices on metallic substrates is that most of the metal foils do not form an ohmic contact with CdTe. We have used Au and Pd as the interlayer. The CdTe film was deposited onto the interlayer by close spaced sublimation. The CdS window layer was deposited by chemical bath deposition onto the CdTe surface and the devices were completed by sputter depositing In:SnO₂. We have studied the effect of post formation annealing treatments of the CdTe/CdS junction on the opto-electronic parameters of the device and correlated the opto-electronic properties with the interdiffusion of Te and S across the CdTe/CdS interface. It was observed that the devices annealed at 400°C show better photovoltaic properties. The Auger depth profile analysis of the CdTe/CdS interface showed that the inter diffusion of Te and S increases with annealing temperature.