Design Of Materials And Optimization Of Device For Polymer/Nanocrystals Hybrid Solar Cells

To relieve and ultimately solve the global energy shortage and environmental pollution,more and more attentions are paid to the research for clean and sustainable solar cells.Polymer/inorganic nanocrystals hybrid solar cells（HSCs）,which combining flexibility,light weight of polymers as well as the properties of adjustable absorption,high extinction coefficient and stability of nanocrystals,are of promising research and application prospects.Aqueous solution processed solar cells are more environmental-friendly and safe for production compared to the organic solvent ones.In this case,a series of innovative research on the materials design,mechanism investigation and preparation technics optimization is developed based on the aqueous solution processed HSCs and other device structures in this paper.There are several critical innovative points on solar cells in this paper:the functional mechanism and optimization methods of interfacial layers are investigated and the power conversion efficiency（PCE）is increased dramatically;a novel processing method to fabricate polymer/nanocrystals bulk heterojunction is constructed,breaking the bottleneck of low efficiencies of HSCs;dip-coating gold nanoparticles film from aqueous solution to fabricate the back electrode of solar cells is established,which can facilitate the cheap and clean production process.Specifically,the works in this paper are summarized as follows:1.In chapter II,the electron transfer layer and hole transfer layer are optimized respectively.For the hole transfer layer,evaporated MoO_x,which is recognized as n-type doped material,is replaced with spin-coated p-type doped organic molecule2,2’,7,7’-Tetrakis[N,N-di（4-methoxyphenyl）amino]-9,9’-spirobifluorene（spiro-OMeTA D）.Increased V_oc and J_scc are achieved attributing to fortified interfacial dipole effect and reduced back recombination loss.For the electron transfer layer,a quasi-bulkpolyporous tin oxide（SnO₂）film prepared from alcoholic solution is applied to replace the high-temperature annealed titanium dioxide（TiO₂）and aqueous SnO₂nanoparticles（NPs）.The fabrication conditions and reaction mechanism of the alcoholic solution processed SnO₂ film are studied in details and relatively high fill factor（FF）as well as PCE are obtained for HSCs.2.In chapter III,a post-permeation method is constructed for fabricating bulk-heterojunction hybrid solar cells.Firstly,polyporous CdTe film is prepared by annealing the mixture solution of aqueous CdTe nanocrystals and cetyltrimethyl ammonium bromide.Then the post-permeation of polymer is employed.By this method,the inorganic nanocrystals and the polymer can be treated under respective optimized annealing temperatures,which can guarantee the removal of ligands and the growth of nanocrystals without damaging the polymers.Additionally,kinds of polymers can be applied regardless of the intermiscibility with the nanoparticles.High PCE exceed 7%（champion one of 7.49%）in polymer/nanocrystals HSCs is achieved by systematical optimization.3.In chapter IV,we demonstrated dip-coated gold NPs films as the back electrode for large-area（50mm²）aqueous-solution-processed HSCs.A PCE of 1.71%of the corresponding all-clean-solution-processed HSC is achieved,which is comparable to its counterpart with vacuum evaporated gold back electrode.This back electrode processing method has great potential for the future mass production for its solution-processing and environmental-friendly properties.In summary,we fabricate efficient and environmental-friendly HSCs via designing and optimizing the interfacial layers and the processing method of active layer,and the working mechanism is researched further.Additionally,aqueous solution processed back electrode is prepared,which enabling the all-clean-solution-processed HSCs.Therefore,this paper is referential for the further optimization of interfacial layers in solar cells,and is instructive for the fabrication of organic/inorganic nanocrystals hybrid bulk-heterojunction as well as the future mass production of solar cells.