Tabitha A. Amollo
Egerton University, Njoro Campus, Department of Physics,
P.O Box 536, Egerton 20115, Kenya. +254 722 70 79 15
Bulk heterojunction (BHJ) device structure is one of the most promising approaches towards high efficiency thin film polymer solar cells (TFPSCs). The conjugated polymer, poly-3-hexylthiophene (P3HT), is the commonly used electron donor while the fullerene, (6-6) phenyl-C61-butyric acid methyl ester (PCBM), forms the electron acceptor in the photoactive layer. This study reports the effect of incorporating graphene derivatives viz graphene oxide (GO) and novel N-doped graphene-germanium quantum dots nanocomposite (NGr-Ge QDs) in the active layer of P3HT:PCBM based TFPSCs. The inclusion of GO and NGr-Ge QDs in the photoactive layer yields high short-circuit current densities (Jsc), which translates to high power conversion efficiencies (PCEs). Also, NGr-Ge QDs in the active layer results in enhanced fill factor (FF). The use of GO in the active layer remarkably improves the optical absorption leading to high charge carriers photogeneration requisite to high Jsc. On the other hand, the nanocomposite in the active layer blend serves to ensure effective charge separation and transportation to the respective electrodes. Consequently, an improvement of up to 120 and 183% in the PCE is achieved by inclusion of GO and NGr-Ge QDs in the active layer of TFPSCs, respectively.
Keywords: Bulk heterojunction, active layer, graphene oxide, N-doped graphene-germanium quantum dots nanocomposite