Thermomechanical Cleave of Polycrystalline CdTe Solar Cells and its Applications: A Review: Article No. 2300074

One of the primary research challenges for cadmium telluride (CdTe) solar cells is addressing its open-circuit voltage (VOC) deficit. While theoretical studies and single crystal work show VOC > 1 V is possible, devices remain stubbornly low at approximately 800-900 mV. As absorber opto-electronic properties (e.g., hole density, carrier lifetime) are improved, device modeling suggests that interfaces become limiting. Because CdTe-based devices are typically grown in the superstrate configuration, the back interface is relatively accessible for manipulation and study, while the front interface (i.e., the heterojunction region) is buried under microns of material and inaccessible. NREL has developed a novel technique to thermomechanically cleave polycrystalline CdTe device stacks directly at the front interface, enabling characterization and controlled manipulation of this important region. Herein, recent work, primarily from NREL, will be reviewed, including considerations for achieving successful delamination; key scientific discoveries about the front interface that have been enabled by this technique; and practical applications, such as flexible, low-cost solar with high power-to-weight ratio.