Fine-tuning optical and electronic properties of graphene oxide for highly efficient perovskite solar cells.

Simplifying the process of fine-tuning the electronic and optical properties of graphene oxide (GO) is of importance in order to fully utilize it as the hole interfacial layer (HIL). We introduced silver trifluoromethanesulfonate (AgOTf), an inorganic chemical dopant, that tunes and controls the properties of single-layered GO films synthesized by chemical vapor deposition. The morphology, work function, mobility, sheet resistance, and transmittance of the GO film were systematically tuned by various doping concentrations. We further developed a solution-processable low-temperature hole interfacial layer (HIL) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PEDOT: PSS):AgOTf-doped GO HIL in highly efficient perovskite solar cells. The PEDOT: PSS:AgOTf-doped GO HIL grants the desirable charge-collection in the HIL allowing the entire device to be prepared at temperatures less than 120 °C. The fabricated perovskite solar cells utilize a rigid substrate and demonstrate compelling photovoltaic performance with a power conversion efficiency (PCE) of 11.90%. Moreover, flexible devices prepared using a polyethylene terephthalate (PET)/ITO demonstrate a PCE of 9.67%, while ITO-free flexible devices adopting PET/aluminum doped zinc oxide (AZO)/silver (Ag)/AZO demonstrate a PCE of 7.97%. This study shows that the PEDOT: PSS:AgOTf-doped GO HIL has significant potential to contribute to the development of low-cost solar cells.