Download or read book Characterization of Electrical Properties of Thin-film Solar Cells written by Rasha A. Awni and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic (PV) solar cells have attracted great attention because of the demand for low cost renewable energy sources. Detailed information on electronic properties, such as doping, defects, gap states...etc, must be fully understood to develop the technology of solar cells. Here, we report the fundamental electronic properties of two distinct materials systems, one is based on polycrystalline cadmium telluride (CdTe) and the other is lead-halide perovskite solar cells. This investigation provides useful information to understand the fundamental nature of single junction solar cell device and material. First, we investigate the impact of back surface treatment method for cadmium sulfide (CdS)/CdTe solar cells using hydroiodic acid (HI) etching to provide an appropriate electrical back contact. The structural properties of CdTe films and electrical properties of the CdTe absorber and interfaces are characterized. Using capacitance-based techniques with the support of current-voltage measurements, we show that the barrier height of the back contact is reduced, apparent doping concentration is increased, and a defect level at 0.409eV is eliminated after the HI-treatment. More importantly, the CdTe device performance is improved. This improvement is still limited by many factors. One factor is the device window layer that limits the current generation. Therefore, we replaced CdS layer by wide bandgap material, ZnMgO (ZMO). We noticed that the electrical properties of CdS/CdTe and ZMO/CdTe solar cells depend on both buffer material and the fabrication atmosphere. Using capacitance spectroscopy-based techniques, we show that CdS/CdTe solar cells have negligible front contact barriers regardless of the fabrication atmospher, while ZMO/CdTe devices show obvious front barriers are dependent on the fabrication atmosphere. Both CdS/CdTe and ZMO/CdTe solar cells have significant back contact barriers. Additionally, we find that the energy level of defects in CdS/CdTe cells is shallower than in ZMO/CdTe cells. These results provide deep insights for understanding and optimizing the performance of CdTe thin-film solar cells. Then, we explored the electrical properties of halide perovskite solar cells (PSCs) that can be deduced by capacitance-based techniques, such as defect activation energy and density, carrier concentration, and dielectric constant. However, we find that these techniques cannot reliably be used to characterize the properties of the defects in the perovskite layer or at its interface. We find that the high-frequency capacitance signature is due to the response of charge carriers in the hole-transport layer (HTL), not in the perovskite layer. In HTL-free PSCs, from the capacitance spectra at high-frequency, the geometric capacitance can be determined and can be used to calculate the dielectric constant of perovskite layers. We also find an overlapping effect with the charge transport layers at the low-frequency capacitance signature in planner PSCs, thus, it cannot be used to analyze the defect properties. However, in the inverted structure PSCs, the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer.