Enhancement in power conversion efficiency of edge-functionalized graphene quantum dot through adatoms for solar cell applications

Abstract

In search of novel, non-toxic and high performance materials for the use in quantum dot solar cells (QDSCs), we have investigated the effect of adatoms (nitrogen, boron and phosphorus) on carboxyl edge-functionalized graphene quantum dot (COOH-GQD) through the state-of-the-art first principles calculation based on density functional theory. The HOMO, LUMO and energy gaps are analysed in order to check the modulation in electronic properties by the foreign atom through hybrid functional B3LYP with 6-31G basis set. Binding mechanism, molecular electrostatic potential (MESP), and charge transfer are investigated to study the electron injection and charge separation in doped/undoped COOH-GQD. Optical properties show broad spectrum in the visible range favorable to harvest solar light. To envisage the application of adatom doped COOH-GQD in QDSC, the solar cell parameters such as open circuit voltage (Voc), Fill factor (FF), short circuit current density (Jsc) and efficiency (η) are presented. The efficiency of COOH-GQD increases by 22–30% after the substitutional doping of nitrogen, boron and phosphorus. Maximum efficiency is achieved in case of phosphorus doping due to its more electron donating nature which will inject more electrons in TiO2 surface. Our findings show that these new sensitizers based on GQD are promising candidates for QDSCs applications.