Abstract:
In renewable energy, solar cell is very actively investigated topic now a days because of sun as limitless source of energy. Among solar cells, organic solar cells are of major focus because of their future possibilities and potential towards cheap and efficient solar devices. Organic photovoltaic (OPV) are devices based on the organic-inorganic interface which use P3HT: PCBM as active layer and metal oxides as electron transport layer. The materials selected are because of the good optical properties, good extinction coefficient, chemical stability, charge mobility and nontoxicity.
ZnO a wide band gap semiconductor is used as electron transport layer due to its good electron mobility. Its band gap lies in ultra violet range which if further reduced the material will fall in the higher wavelength visible range effecting both light harvesting by the devices and enhancing exciton disassociation and extraction. In this work Molybdenum di-sulphide MoS2, a low band gap two dimensional material is used for the band gap engineering of ZnO and its effects are studied on the current Isc, current density Jsc and fill factor.
Band gap of ZnO was reduced from 3.34eV to 2.92 eV. UV-Vis spectroscopy and cyclic voltammetry techniques were used to verify the reduction in band gap, results obtained by both techniques in agreement with each other with in the limits of experimental errors. XRD results confirmed the imbedding of MoS2 in ZnO thin films. Also SEM and AFM images of ZnO films verified very fine nano-particles, and images of exfoliated MoS2 showed very few layers of MoS2 of thickness 0.939 nm. The Fill factor and short circuit current showed increasing trends due to increasing MoS2 concentration in ZnO thin films reflective of increase in electron mobility due to incorporation of MoS2. Based on these results ZnO-MoS2 composite can be an efficient electron transport material for use in thin film photovoltaics.
