Laser-induced graphene electrode based flexible heterojunction photovoltaic cells

Graphene based nanomaterials have attracted significant research interest due to their unique optoelectronic properties which can be tuned to tailor the functionalization in various photovoltaic (PV) applications. These PVs are capable of powering various wearable and flexible electronic devices such as touch-panels, light-emitting diodes (LEDs), sensors, high speed field effect transistors (FETs), etc., which can be a low-cost alternative to traditionally employed silicon solar cells. However, in terms of processing performance and electrical properties, current methods of manufacturing graphene-based PVs have numerous drawbacks. Therefore, there is a need for more effective fabrication methods with commercial feasibility and roll-to-roll processing of graphene-based PVs. This article is the first to present a laser-based patterning technique for fabricating graphene electrodes from polyimide that are compatible with flexible and thermally sensitive substrates for solar cell applications. A heterojunction PV, with ferroelectric Cr-doped BiFeO3 (BFCrO), was deposited on the flexible graphene as the energy harvesting layer sandwiched between p-NiO and n-WS2 window layers. Subsequently, its PV performance was compared with the similar multi-junction PV built on the Indium‑tin Oxide (ITO) one. The LIG electrode outperformed the ITO with its excellent stability, flexibility, and conductivity. The maximum power conversion efficiency (PCE) culminated was 5.20% which is around 5 folds enhancement when compared to the ITO based PV. Furthermore, after bending graphene electrode to 130°, the sheet resistance returned to its original value, while the resistance of ITO increased due to the cracking effect. With these unique properties, LIG electrodes can be promising for the development of flexible ferroelectric BFO based heterojunction PV devices.