چكيده به لاتين
In this thesis, practical designs have been provided to overcome the low efficiency and VOC deficit in kesterite based solar cells by several proposing practical structures, changing buffer layer, inserting p+-CZTSSe ultrathin layer between Mo and p-CZTS layer, and using dual absorber layer. The effect of various layers and interface parameters such as thickness, carrier concentration, defect density and current recombination are studied, carefully. First, the results of the structure with 12.03% efficiency are reproduced to verify the validity of the simulation. Then, the results of the five efficient CZTS/CdS-based solar cell experimental structures are scrutinized and two CZTS solar cells with 8.4% and 11% efficiency reproduced, and validated. Additionally, a p+pn structure (p+-CZTSxSe(1-x)/p-CZTS/n-CdS) has been designed to improve simultaneous of the efficiency, open-circuit voltage and short-current density of the solar cell. In CZTSe/CZTS-based structure, the device conversion efficiency is increased to 15.98% at the condition of the 50 nm CZTSe thickness and the carrier concentrations of 1×1017cm-3 and 1×1018cm-3 for CZTSe and CZTS layers, respectively. In addition, the best band alignment in CZTSxSe1-x/CZTS-based structure leads to an efficiency of 17.22% by selecting x=0.2 as CZTS0.2Se0.8, with a band gap of 1.09eV. Furthermore, the device conversion efficiency is enhanced to 17.81% at the condition of the 50 nm CZTS0.2Se0.8 thickness and the carrier concentrations of 1×1018cm-3 and 5×1016cm-3 for CZTS0.2Se0.8 and CZTS layers, respectively. In continue, it is shown that it is possible to increase the efficiency and open circuit voltage of kesterite solar cell to respectively 15.62% and 919 mV through inserting CZTS as a BSF layer with a thickness of 200 nm and carrier concentration of 1×1018 cm-3. Moreover, dual CZTS absorber layer with p+pn structure is proposed to enhance the photovoltaic parameters. In this dual absorber-based structure, the device conversion efficiency increases to 17.05% by selecting the thickness of 1 µm and the carrier concentration of 1×1018 cm-3 for the p+-CZTS layer and choosing the carrier concentration of 5×1015 cm-3 for the p-CZTS. In addition, the efficiency of this structure with 5.1 eV work function of back-contact is 19.08%.
