Nitrogen-doped graphene quantum dots/ polyvinyl alcohol nanocomposite for photon management: Application in CIGS photovoltaic cells

The efficiency (η) of copper indium gallium selenide (CIGS) solar cells has been hampered by absorption losses that happen within the ZnO and CdS layers. A photon downconversion layer created from polyvinyl alcohol (PVA) and nitrogen-doped graphene quantum dots (NGQDs) composite (NGQDs/PVA) was implemented on the top of the cell to overcome this obstacle. Notably, the NGQDs/PVA layers, prepared at spin speeds of 3000, 4000, and 5000 rpm, exhibited optimal characteristics, demonstrating superior light absorption at low wavelengths along with elevated transmittance at longer wavelengths. The η was found to be highest for the layer prepared at 4000 rpm, accompanied by elevated values of short-circuit current (J_sc), open-circuit voltage (V_oc), and fill factor (FF). Consequently, Cell #2 incorporating the champion NGQDs/PVA layer outperformed all other CIGS photovoltaic cells, showcasing an impressive enhancement of 8.96 % in J_sc, 1.62 % in V_oc, 2.03 % in FF, and an overall η of 11.51 %. This champion cell significantly improves the performance of CIGS photovoltaics.