Publication
The earth-abundant and non-toxic material Zinc phosphide (Zn3P2) is a promising candidate for solar cell applications. However, growth of defect-free, high-quality thin films on substrates that can integrate with current technology (e.g. silicon) remains challenging. The use of buffer layers, such as graphene, have emerged as promising methods for growth and device fabrication, yet a comprehensive understanding of its optoelectronic properties of the Zn3P2 thin film within these architectures is essential. Terahertz spectroscopy is a powerful, contact-free and non-invasive characterisation tool with high precision in time domain which has been widely employed for investigating the carrier dynamic and electronic properties of the material. In this work, we operate the optical-pump terahertz probe (OPTP) spectroscopy and terahertz time-domain spectroscopy (THz-TDS) on Zn3P2-based samples grown on both InP and Si substrates and with an incorporated graphene buffer layer engineered for solar cell devices. From the experimental response, the carrier lifetime, carrier mobility and dielectric function of the corresponding samples are extracted for enhancing the device performance. We also discuss challenges with analysing the response and extracting key device parameters, for the case where the buffer layer is included. These results open up pathway for utilizing terahertz spectroscopy on device architectures in future.