Investigation on Carrier Dynamics and Photovoltaic Performance of Czts Materials

The main objective of this project is to achieve the low-toxicity and high-efficiency photovoltaic devices. Cu2ZnSn(S,Se)4 (CZTS), having the kesterite structure, is one of the most promising absorber layer candidates for low cost thin film solar cells, because of its suitable direct band gap between 1.4 and 1.56 eV and large absorption coefficient, over 104 cm-1. Research categories include both fundamental physics and practical implementation. Improving CZTS device performance will require better understanding of the link between material properties and processing, and their influence on junction characteristics, carrier collection, and recombination mechanisms. Carrier dynamics will be examined using TRPL, CAFM, SCM, Raman spectra and discussed in detail. In phase-I stage, we use the thermal evaporation, sputtering and selenization systems to prepare high quality CZTS absorber layer. The aim of this stage is to develop pure CZTS thin films without secondary phases and realized the rectification characteristic. The conversion efficiency of 6% is expected to be demonstrated. In phase-Ⅱstage, the CZTS solar cells with Cd-free buffer layer will be the main mission, and we expect the conversion efficiency of Cd-free solar cells can exceed 8%. Meanwhile, a non-uniform layer of nanocrystal quantum dots aggregates is deposited between the transparent conductive oxide and a CdS/CZTS p-n junction using low cost pulsed-spray deposition. This work is important in developing non-toxic, Earth-abundant elements thin-film solar cell. In phase-III stage, an effective approach is demonstrated for enhancing photoelectric conversion of CZTS solar cells with three-dimensional ZnO-based nanostructures. Under a simulated one-sun condition, the conversion efficiency of cells with ZnO-based nanostructures can exceed 10%. This enhancement in light harvesting is attributable to the gradual refractive index profile between the ZnO nanostructures and air. The omnidirectional anti-reflection of CZTS solar cells with various ZnO-based nanostructures is also investigated. Meanwhile, we propose a nanostructured CZTS PV device based on Mo nanorods and thermal evaporation derived CZTS thin film. The advantages of nanostructure and conventional CZTS will be integrated in a single PV device. The achievements of this project can make substantial progress in developing CZTS solar cells providing environmental and manufacturing benefits.

Project ID:PA10408-0738
External Project ID:MOST104-2112-M182-005