An insight into atmospheric plasma jet modified ZnO quantum dots thin film for flexible perovskite solar cell: Optoelectronic transient and charge trapping studies

In this work, a new embodiment of flexible perovskite solar cell is based on graphene (Gr) as the barrier layer and the atmospheric plasma jet (APjet)-treated ZnO quantum dots (QDs) as the mesoscopic metal oxide layer on ITO-PET substrates. The ITO-PET flexible substrate was treated with oxygen (O₂) plasma before creating an efficient barrier layer of Gr, and thereafter as-synthesized ZnO QDs were deposited by spin coating on ITO-PET/Gr thin film. ITO-PET/Gr/ZnO-QDs thin film substrates were finally subjected to APjet treatment using RF power of ∼40 W with frequency of ∼13.56 MHz, which substantially improved the interfacial properties of the deposited layers. The fabricated ITO-PET/Gr/ZnO-QDs(APjet)/CH₃NH₃PbI₃/spiro-MeOTAD/Ag flexible perovskite solar cell obtained the high conversion efficiency of ∼9.73% along with high short circuit current (J_SC) of ∼16.8 mA/cm², open circuit voltage (V_OC) of ∼0.935 V, and high fill factor (FF) of ∼0.62. The APjet treatment on ITO-PET/Gr/ZnO QDs thin film enhanced the performances and the photocurrent density as compared to other solar cells fabricated without APjet treated ITO-PET/Gr/ZnO QDs thin film. By analyzing the intensity-modulated photocurrent (IMPS)/photovoltage spectroscopy (IMVS), the fabricated flexible perovskite solar cell exhibited a good charge transfer rate and a reduction in the recombination rate. The APjet treatment and the introduction of low-cost Gr barrier layer are promising prospects to approach low cost photovoltaic devices.