Development of hybrid solar cells based on TiO₂ or ZnO- graphene oxide heterojunctions

Nowadays it is becoming increasingly necessary to find alternatives to fossil fuels in order to produce energy from renewable sources that do not have a negative impact on the environment. In this work, two types of hybrid solar cells devices were produced, in which the photoactive layer is made of poly (allylamine chloride) (PAH) and graphene oxide (GO) organic films and titanium dioxide (TiO2) or zinc oxide (ZnO) inorganic films. These films were deposited on fluoride-doped tin oxide (FTO) glass substrates, being the organic layer deposited by the layer-by-layer (LbL) technique and the inorganic layer by DC-reactive magnetron sputtering. The aluminum electrodes were deposited by thermal evaporation. The final device configuration was FTO/(PAH/GO)x/TiO2/Al and FTO/(PAH/GO)x/ZnO/Al, where x is the number of bilayers deposited. (PAH/GO)x films were characterized by ultraviolet-visible spectrophotometry, which revealed a linearity in the growth of the films with the number of bilayers. Scanning electron microscopy (SEM) showed that the morphology of the inorganic layer is homogeneous and is dependent on the number of layers of the organic layer. The SEM cross section images further revealed the desired architecture. The electrical properties were characterized by constructing current-voltage curves. The FTO/(PAH/GO)50 /TiO2/Al, FTO/(PAH/GO)30/ZnO/Al and FTO/(PAH/GO)50/ZnO/Al devices were the only ones to exhibit a diode behavior, although they did not show any reaction when exposed to light. The FTO/ (PAH/GO)50/ZnO/Al cell experienced a decrease in current when characterized in a low humidity environment, revealing that humidity is a key factor in the conduction of the organic films.