Optoelectrical Properties and the Study of Thickness and Annealing in Poly-3-hexylthiophene Based ITO Free Organic Solar Cells with TiO2 and MoO3 as Transport Layers

Inverted organic photovoltaic solar cells were fabricated with the configuration of FTO/TiO2/P3HT:PC61BM/MoO3/Ag. Besides, the influence of transport layers, titanium dioxide and molybdenum trioxide, on the performance of solar cells were investigated. These compounds showed excellent optical (around 80% for molybdenum trioxide and 95% for titanium dioxide), electrical (like charge carrier density of 3.3 x1015 cm-3 and 2.5 x1014 cm-3 for titanium and molybdenum, respectively) and structural (anatase and amorphous hexagonal phase for titanium and molybdenum, respectively) properties to be used as transport layers. Also the influence of the thickness of the electron transport layer is studied, as well as the thickness, temperature and heat treatment time of the active layer. The correct selection of TiO2's thickness (70 nm) and active layer's thickness (250 nm) and annealing (at 100 degrees for 8 minutes) can increase the power conversion efficiency. Moreover, the cell fabricated with transport layers and the best conditions found showed a maximum efficiency of 3.3%, which indicates that the titanium dioxide and molybdenum trioxide played a determining role in the solar cell performance.