Grain-to-Grain Epitaxy of Polycrystal CdTe Thin Film via Molecular Beam Epitaxy

Even though the recent record of Group-V doped cadmium telluride (CdTe) photovoltaics (PV) is reaching 23% efficiency, a lack of understanding of fundamental materials science of Group-V doped CdTe is limiting dopant activations, open circuit voltage (VOC) gains, and improved device performance. The ability to synthesize high-quality polycrystalline (pX) CdTe thin films under a highly controlled environment is thus crucial for scientific inquiries and for improving our understanding of Group-V doping in pX CdTe thin films. In this work, we present MBE-grown pX CdTe thin film on a variety of pX templates with different grain sizes. This material platform fill in the current research and engineering gap between a high-quality single-crystal (sX) MBE CdTe study and manufacturing setting vapor transport deposition (VTD) pX CdTe development. We present a collection of successful pX CdTe thin films and their arsenic incorporations with no strain or structural interruption between the MBE layer and pX templates. Characterization techniques, including electron backscatter diffraction (EBSD) and secondary ion mass spectrometry (SIMS), are employed to evaluate the structure and dopant incorporations of the resulting films. By leveraging the advantages of MBE and pX templates, the findings of this work introduce a new angle and platform to study the fundamentals of pX CdTe materials and the current limitations of the CdTe PV manufacturing process.