| Nowadays energy crisis and environmental pollution are hot topics of the world.Developing safe,environmentally friendly and sustainable energy is one of the major issues of the mankind.Solar energy,as one of the clean and renewable energy,has attracted widerspread attention in academia and industry.Solar cells,exploiting the photovoltaic effects,transform solar energy directly into electricity.Among them,thin-film solar cells have the advantages of low production cost,high power conversion efficiency and good device stability.What is more,they could be processed into flexible modules for a wide range of applications.Compared with vacuum deposition techniques,solution process for thin-film solar cells has many advantages.It requires significantly lower capital cost of the manufacturing equipment and enables fast deposition rates analogous to paper printing.What is more,solution-based deposition can realize uniform doping and composition uniformity over large area,and enable high utilization of raw materials.Based on these advantages and prospects,this paper focuses on solution-processed thin film solar cells.The research goal is to produce stable and efficient solar cells through a simple,reproducible,low-cost and environmentally benign strategy.Spefically,we developed a general strategy to use water as the only solvent to obtain a series of metal chalcogines complexes(MCCs)solution,and then applied these solutions to construct metal chalcogenide thin films and eventually we achieved stable and high-efficiency thin film solar cells.In this paper,the following work has been carried out:(1)We innovatively explored a general method to fabricate a series of metal chalcogenide complexes(MCCs)aqueous solution,denoted as water-MCCs.Using water as the only solvent and(NH4)2S as the additive,we synthesized large-scale V2VI3(V= As,Sb;VI=S,Se,Te)solution.Based on solution's Raman analysis,V2VI3(V= As,Sb;VI=S,Se,Te)exists as long-chain Mx(S,Se)Yn-(M=As,Sb)in the solution.The accomplished results in this part of the work has laid a solid foundation for the follow-up film preparation,exploration of new materials and synthesis of nano-ink for solar cells.(2)Fabrication of MCC thin films and solar cells.Taking advantages of Sb-based MCC,we employed spray pyrolysis to fabricate Sb2(S1-x,Sex)3 thin films with ajustable band gaps.What is more,combined with TiO2 thin film prepared by sol-gel method,the device generated a power conversion efficiency of 1.43%.(3)Based on MCCs aqueous solution,new materials for photovoltaic application were emplored.NaSbS2 possesses the mixed ionic and covalent bonding nature,in analogy to the high-efficiency halide perovskites.We explored the charateristics and photovoltaic applications of NaSbS2.Phase pure NaSbS2 thin film was successfully fabricated using spray-pyrolysis method,and its optical and electrical properties were studied.Finally,a prototype NaSbS2-based thin-film solar cell has been successfully demonstrated,yielding a power conversion efficiency of 0.13%.(4)Preparation of aqueous MCCs,specifically Sb4S72-,which can serve as ligands for in-situ synthesis of water-based PbS quantum dots(QDs).We achieved a homogeneous and stable aqueous QDs solution without further conventional secondary ligand exchange,laying a solid foundation for the follow-up synthesis of multi-compound nano-ink.(5)Utilize water-MCCs to produce self-stabilized Cu2ZnSnS4 nano ink and high-efficiency Cu2ZnSn(S,Se)4 solar cells.Solution-processed MCC Sn2S64-and Sn2S76-were employed as the self-component ligands to in-situ cap the Cu/Zn sulfide nanoparticles,resulting in homogeneous and stable nano ink.Then the solvent and impurity removal process and the film forming mechanism were studied in detail.Finally,after applying post-sintering procedure and adjusting film doping,the power conversion efficiency of 8.48%has been achieved for CZTSSe solar cell,demonstrating the potential of aqueous MCCs for fabrication of efficient thin film solar cells. |
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