IEEE PVSC 49
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SPLTRAK Abstract Submission
Use of a Selenium-Telluride Alloy as a Back Interface for CdTe-Based Cells
Daniel Z. Shaw, Camden L. Kasik, Andrew C. Treglia, James R. Sites
Colorado State University, Fort Collins, CO, United States

Use of a Selenium-Telluride Alloy as a Back Interface for CdTe-Based Cells
Daniel Z. Shaw, Camden L. Kasik, Andrew C. Treglia, and James R. Sites
Colorado State University, Fort Collins, CO 80523, United States

Cadmium telluride (CdTe) based thin-film photovoltaics have proven to be a viable and cost-effective solution energy solution.  While advancements have been made thanks to the high current density of the devices, a limiting factor has proven to be the difficulty in raising the open-circuit voltage.  One approach is to use band bending at the back of the device and create an “electron reflector”.  The theory behind this layer is that the photo-generated holes will be more easily extracted via the back contact and reduce recombination with the created photoelectrons.  This reduces the impact of the Schottky barrier formed by metal back contacts with lower work functions.  For this to be effective, the back layer should have a higher band gap and an intermediary valance band maximum (VBM) between CdTe (5.8 eV below the vacuum level) and the work function of the back contact (5.2 eV for Ni).
 
A variable tellurium content in a selenium telluride alloy (Se1-xTex) was applied to thin film CdTe based photovoltaic devices as an electron-reflector layer.  Comparing tellurium contents of 10%, 50%, and 70%, and varying the thickness of the layer between 15 and 30nm; led to an initial optimization of the layer.  The resulting devices showed that a thicker SeTe layer would result in lower efficiencies, and a lower tellurium content (10%) performed better in terms of Voc and fill factor most notably. These selenium rich devices show great initial promise, reaching efficiencies of 19.1%.