Performance efficiency of an organic solar cell FTO:PTB7:PC70BM free of ITO and its degradation

Abstract

The expensive ITO has widely been used as an electrode for fabricating organic photovoltaic solar cells (OPV), which turns out to be an obstacle to the commercialization of solar cells. Therefore, in this work, we aim to replace the ITO with fluorine-doped tin oxide (FTO), which is 40 times cheaper than ITO. Besides, titanium dioxide is used as an electron transport layer instead of zinc oxide (ZnO). The active layer comprises the conductive polymer PTB7 as a donor and the fullerene derivative of PC70BM as an acceptor. The inverted OPV is fabricated with FTO/TiO2/PTB7:PC70BM/MoO3/Ag device structure. The fabricated OPV showed a power conversion efficiency (PCE) of 0.48%. Therefore, to enhance the PCE of the OPV, the device parameters such as the thickness of each layer, thermal treatment of the active layer and the OPV are optimized. As a result, the PCE is greatly enhanced from 0.48% to 2.88%. Furthermore, the open-circuit voltage, short circuit current density, and fill factor are significantly improved. The degradation efficiency measurements are reported. Hence, this research demonstrates a new pathway towards enhancing the OPV with stable, non-toxic and low-cost materials.