Synthesis And Application Of Nanocarbon Materials In Novel Solar Cells

Dye-sensitized solar cells(DSCs)and perovskite solar cells(PSCs)regarded as the third generation solar cells are promising due to their low cost and high conversion efficiencies.Precious metals such as Pt or Au are usually used as counter electrode for DSCs and back contact for PSCs.However,the high cost and limited availability of precious metals is very likely to hamper the industrial deployment of PSCs and PSCs.Compared to precious metals,carbon materials such as carbon nanotubes and graphene have unique properties such as excellent conductivity,high transparency,ease of modification and low cost,which make them promising candidates for DSCs and PSCs.In this thesis,carbon materials were prepared and applied as highly efficient counter electrode for DSCs,and as hole extraction material and conductive back contact as well as transparent electrode for PSCs.Firstly,nitrogen and sulfur dual-doped reduced graphene oxide was synthesized by using DL-penicillamine as nitrogen and sulfur sources and introduced into DSCs in conjunction with disulfide/thiolate,triiodide/iodide and cobalt-polypyridine redox mediators and quantum-dots sensitized solar cells(QDSCs)coupled with aqueous polysulfide electrolyte as counter electrode catalytic material for the first time.Nitrogen and sulfur dual-doped reduced graphene oxide showed not only similar catalytic activity to Pt in conjunction with triiodide/iodide mediator,but also superior catalytic activity in conjunction with the disulfide/thiolate,cobalt-polypyridine and polysulfide mediators,making it a high catalytic and versatile counter electrode for the low-cost manufacture of high efficiency DSCs and QDSCs.Secondly,reduced graphene oxide was prepared by reducing the graphene oxide with ferrous iodide acid solution and the as-prepared highly conductive reduced graphene oxide was combined with dopant-free spiro-OMe TAD as hole extraction and transport material in PSCs.The results showed that the higher of the conductivity and hole mobility of reduced graphene oxide,the higher of power conversion of the PSCs.Furthermore,PSCs based on reduced graphene oxide greatly outperformed the reference PSCs based on pure dopant-free spiro-OMe TAD.Impressively,PSCs with reduced graphene oxide showed significantly improved air stability compared to the device with Li-TSFI and pyridine doped spiro-OMe TAD,remained above 85% of the initial value even after 500 h of storage in air.Thirdly,cross-stacked superaligned carbon nanotubes was applied as back contact in hole conductor-free PSCs for the first time.The influence of layer numbers of carbon nanotubes on the photovoltaic performance of PSCs was investigated.Moreover,by doping the cross-stacked superaligned carbon nanotubes with iodine,the power conversion efficiency of the hole conductor-free PSCs can be further improved resulting from the increased grain size and improved crystallinity of perovskite in the carbon nanotube films as well as the enhanced conductivity of the iodine doped cross-stacked superaligned carbon nanotubes.Additionally,PSCs encapsulated with PMMA show outstanding ambient stability in the dark and highly humid conditions.Finally,flexible PSCs based on graphene transparent electrode and cross-stacked superaligned carbon nanotubes back contact were fabricated for the first time.By using PCBM modified low-temperature synthesized Ti O2 as selective electron contact and spiro-OMe TAD as the hole collecting material,a power conversion efficiency of 4.12 % for the all carbon-electrode-based PSC was obtained.Furthermore,the flexible PSCs exhibited excellent mechanical flexibility,retaining 89% of the original power conversion efficiency even after 500 bending cycles.