SPLTRAK Abstract Submission
Tellurium Oxide as a Back-Contact Buffer layer for CdTe Solar Cells
Camden L Kasik, Ramesh Pandey, Akash Shah, James R Sites
Colorado State University, Fort Collins, CO, United States

The open circuit voltage (Voc) for CdTe based photovoltaic devices is still well below the Schockley-Queisser limit, and is the major issue limiting device performance. One way of improving the Voc  is by reducing recombination at the back contact. In this work we discuss the use of a thin buffer layer of tellurium oxide () at the back of the cell to passivate defects, bend bands upwards, and eliminate the need for copper doping. The effects of  on device performance are characterized by current-voltage measurements, showing efficiencies and open-circuit voltages up to 17.5% and 829 mV without external doping. Admittance and capacitance voltage measurements are used to study the depletion width and carrier concentration, while time resolved photoluminescence measurements are used to explore the effects on recombination. Temperature dependent current-voltage measurements were used to inspect the back barrier. We found  cells with carrier densities up to 1e15 carriers per cubic centimeter and carrier lifetimes up to 160 ns. Our results demonstrate the viability of  as a buffer layer to improve passivation in CdTe solar cells. An added benefit of  is the ability to utilize an undoped absorber, which is crucial to reduce degradation in CdTe solar cells.