Study On Electrochemical Properties Of Graphene Oxide

Graphene is a one-atom-thick planar sheet which consists of sp²-bonded carbon atoms densely packed in a honey comb crystal lattice.It exhibits exceptionally excellent optical,electrical,mechanical and morphological properties and could be an attractive choice of material for use in many fields such as supercapacitors,photonic and electronic devices,Li-ion batteries,and solar cells.In present dissertation,we developed a simple,facile,low-cost and green electro-reduced method to prepare highly quality graphene with excellent optical transparency,carrier mobility,and compatible work function level.The as-prepared graphene oxides?GO?and electrochemical reduced graphene oxides?ERGO?were employed as the hole transport layers?HTLs?for hybrid lead-halide perovskite solar cells?PSCs?.The inverted?p-i-n?thin-film perovskite solar cells with a planner heterojunction?PHJ?configuration were fabricated.The performances and charge-extraction behaviors of aforementioned PSC devices were investigated.?1?GO was synthesized according to a modified Hummers method and deposited on an In-doped SnO2?ITO?substrate that was prepared by magnetron sputtering technique through drop-casting.The ITO/GO substrate was used as working electrode to perform the electro-reduction experiments to give ITO/ERGO sample.The preparations of GO and ERGO were investigaed.The results indicated that the oxygen-containing functional groups?such as hydroxyl,epoxy group,and carbonyl?in GO could be removed effectively to give ERGO with improved conjugation properties.Both GO and ERGO exhibited continuously planner structures.However,the electrochemical reduction process would introduce defects into the structure of ERGO.The CV curves of ITO/ERGO electrode maintain a relatively rectangular shape under various potential scan rates,evidently indicating the excellent capability of ERGO.Besides,it was found that the conductivity was largely improved by the electrochemical reduction.?2?The PHJ PSC devices were fabricated with an inverted p-i-n configuration ITO/GO?ERGO?/CH₃NH₃PbI₃/PCBM/Ag.The GO/ERGO HTLs,perovskite CH₃NH₃PbI₃light harvesting layer and PCBM electron transport layer were spin-coated onto the ITO substrates to form a layer-by-layer struture.The silver back-contact electrode was eventually deposited via thermal evaporation in a vacuum chamber.The resultant PSC device with the architecture of ITO/ERGO/CH3NH3PbI3/PCBM/Ag provided excellent and reproducible power conversion efficiency of up to 9.26%,which was superior to the GO-based device.The investigation revealed that the improved performance of ERGO-based device was due to the facilitated charge collection with a retarded recombination and high conductivity of ERGO.Moerover,the ITO/ERGO/CH₃NH₃PbI₃/PCBM/Ag device maintained 60%of its initial efficiency after storage for 10 days,indicating the excellent long-term stability of the ERGO-based device.The observations demonstrated the realization of low cost,facile manufacturing PSC device along with the high performance and excellent stability.