The electrical characteristics of ITO/CZTS/ZnO/Al and ITO/ZnO/CZTS/Al heterojunction diodes

In this study, ITO/a-CZTS/ZnO1/Al, ITO/ZnO2/a-CZTS/Al and ITO/ZnO2/c-CZTS/Al diode structures were produced by PLD technique and analysed, as well as data are presented. a-CZTS and ZnO thin films were grown as layer by layer thin films on ITO coated glass at room temperature and annealing process was not carried out for these samples. Morphologies and crystal structures of ZnO and a-CZTS thin films were analysed. ZnO thin films have been produced depending on an oxygen ambient gas pressure and a-CZTS thin film has been produced using low laser energies. While ZnO thin films exhibit crystal structure, a-CZTS has amorphous structure. In addition, c-CZTS thin film has also been annealed at 375 °C sulfurization temperature at which crystalline structure was obtained. Optical features of thin films were determined by UV–vis spectra and it was observed that a-CZTS and c-CZTS thin films have a high band gap and an ideal band gap, respectively. Diode structure of ITO/a-CZTS/ZnO1/Al has shown normal diode characteristics in dark environment and has different ideality factors for three regions in semi-logarithmic forward bias region. ITO/ZnO2/a-CZTS/Al diode structure has also shown a negative differential resistance and behaved like a tunnelling diode in dark environment exhibiting photoelectric effect under illuminated environment. Short circuit current density is very low, fill factor and open circuit voltage are quite high. In addition, ITO/ZnO2/c-CZTS/Al diode structure has shown some photo-electricity property under illumination conditions. The diode's short circuit current density was found to be higher and open circuit voltage was very low. Electrical characteristics of diodes have been described in some details in this work.