Nanoscale investigation of grain boundary characteristics of single-crystalline-like GaAs films and solar cells on flexible metal substrates

High-resolution imaging with nanometer spatial resolution was carried out to unravel the grain and grain boundary (GB) properties of single-crystalline-like n-type GaAs films and single-junction solar cells on epi-ready flexible metal substrates. Electron Back Scattered Diffraction studies revealed ultra-low angle GBs with the presence of twin boundaries. The pn junction carrier collection properties were directly imaged using cross-sectional Electron Beam Induced Current measurements. Low-temperature Cathodoluminescence imaging indicated a strong component of optical emission from the GBs. Comprehensive studies of the structural, chemical, optical and electrical properties were carried out to unravel the fundamental GB properties of flexible GaAs films on metal substrates.