Thermomechanical Cleave of Polycrystalline CdTe Solar Cells and its Applications: A Review

One of the primary research challenges for cadmium telluride (CdTe) solar cells is addressing its open-circuit voltage (V-OC) deficit. While theoretical studies and single crystal work show V-OC > 1 V is possible, devices remain stubbornly low at approximate to 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.

Automated summary

One of the main challenges in the research of cadmium telluride (CdTe) solar cells is their low open-circuit voltage (V-OC) of approximately 800-900 mV, despite the theoretical possibility of V-OC > 1 V. Improvements in the opto-electronic properties of the absorber material suggest that the interfaces become limiting factors. NREL has developed a novel technique to cleave polycrystalline CdTe device stacks at the front interface, allowing for characterization and manipulation of this important region. This technique has led to key scientific discoveries and practical applications in flexible, low-cost solar cells with a high power-to-weight ratio.