Studies of compositional dependent CZTS thin film solar cells by pulsed laser deposition technique: An attempt to improve the efficiency

摘要

The performance of CZTS thin films deposited by using pulsed laser deposition technique is investigated as a function of target composition. The chemical composition ratio a = Cu/(Zn + Sn) of the target material has been varied from 0.8 to 1.2 in step of 0.1 by keeping Zn/Sn constant. The effect of the chemical composition in the precursor thin films on the structural, morphological, chemical and optical properties of the CZTS thin films has been investigated. X-ray diffraction and X-ray photoelectron spectroscopy studies showed that the annealed CZTS thin films are of a single kesterite ciystal structure without any other secondary phases. The direct band gap energy of the CZTS thin films is found to decrease from 1.72-1.53 eV with increase of 'a'. The estimated band-gap energy from the quantum efficiency measurements is about 1.54 eV. The solar cell fabricated with Glass/Mo/CZTS/CdS/ZnO:Al/Al structure grown using [a = Cu/ (Zn + Sn) = l.l] showed the best conversion efficiency of 4.13% with V_(oc)- 700mV, J_(sc)= 10.01 mA/cm~2 and FF = 0.59.