Improving the photovoltaic parameters in CdS quantum dot sensitized SnO2 based solar cells through incorporation of chemically deposited compact SnO2 layer

Abstract

Mitigation of the recombination of electrons within the quantum dot sensitized solar cells (QDSSCs) and hence the improvement in the performances of the devices can be achieved by incorporation of a compact layer in between the transparent conducting substrate and the semiconducting materials used in these devices. In this work, a facile and cost-effective method of incorporation of a compact layer of SnO2 over the Fluorine doped Tin oxide (FTO) substrate and its effect on the efficiency enhancement of the CdS sensitized SnO2 QDSSCs have been studied by means of current-voltage characteristics, Electrochemical Impedance Spectroscopy, and electron lifetime estimation. The incorporation of the SnO2 compact layer improved the overall efficiency of the device by 250% as compared with the devices fabricated with no compact layer under the illumination of 100 mWcm-2. The improvement in the open-circuit voltage and the significant enhancement in the short circuit current density (~200%) together with the increase in the electron lifetime in the QDSSC with the compact layer suggested that the compact layer has acted as a weak energy barrier, which increased the electron density in the mesoporous SnO2 film. The enhancement in the short circuit current density and the efficiency mainly stems due to the decrease in the series resistance and the increase in the recombination resistance of the device fabricated with the compact layer.