| The depletion of fossil energy and the severe situation at home and abroad have made the energy crisis more serious,and the overexploitation of traditional fossil energy and the emission of secondary organisms have also caused serious environmental and social problems,and the development of clean energy has become more and more important.Among them,solar cells have attracted widespread attention because of their advantages of no pollution,no noise,low maintenance cost and long service life,and related industries have also flourished,among which the most concerned is perovskite solar cells(PSCs).The battery has high efficiency(single-layer battery exceeds 25%,tandem cell can even reach 30%),low cost of use(perovskite raw material resources are abundant,cheap),easy processing and preparation,simple process(low temperature processing,solution processing,spraying printing),rich use scenarios(can prepare flexible batteries,etc.),if reasonable design technology upgrade will have high economic value,it is expected to replace the subversion of the current crystalline silicon solar cells.There are two main problems in the development of PSC,one is the cost of power generation,whether the photoelectric conversion efficiency can continue to improve,which is the foundation of solar cells;One is whether the stability can be guaranteed,and the short life of water and oxygen is also the biggest disadvantage of PSC now.After the solar cell is illuminated,holes and free electrons will be generated inside it,and the free electrons flow due to the potential difference to generate current.In PSC,the work of the electron transport layer(ETL)is,as the name implies,to transmit mobile electrons,which plays an important role in the photoelectric conversion efficiency and stability of the device.At present,the mainstream ETL material in trans structure PSC is fullerene and its derivatives,but there are also many shortcomings in its use,such as high cost of use,difficult to optimize energy level,short service life,etc.,which determine that it is difficult to apply and actuallyVII produce at present,and is one of the industrialization bottlenecks of trans structure PSC in the future.In order to solve the above problems and achieve commercial application as soon as possible,relevant practitioners have set their sights on the development of high-performance non-fullerene electronic transport materials.At present,non-fullerene electron transport materials are mainly divided into colimide,naphthimide,and polycyclic aromatic hydrocarbons,of which the synthesis cost of polycyclic aromatic hydrocarbons is high,and the current development of colimide,naphthimide HTM in trans PSC application effect is not ideal.Acetylimide HTM has poor solubility,and it is easy to aggregate disorderly during spin coating,reducing electron mobility.In the existing research,it has been found that naphthimide(NDI)molecules have the advantages of easy to design and modify the structure,adjustable and optimized energy level,low price,and good processing performance,which is very promising.In this paper,for the purpose of improving the work efficiency,reducing production and use costs and improving the working stability of perovskite solar cells,a series of small molecule electron transport layer materials based on ring sides replaced by NDI units are designed and synthesized: NDI-N,NDI-N,NDI-N,and NDI-NN.and small molecules based on NDI-thiophene units: NDI-OL,NDI-N-OL,NDI-NN-OL,prepared into ETL for trans perovskite solar cells.Synthesis and device application of nanomolecular electron transport layer based on bay nitrogen-containing group substitute for naphthimide With naphthimide small molecules(NDAs)as the matrix,ndi-n,ndi-NH and NDI-NN with three different nitrogen-containing substituents and different chain length substituents on three sides were designed and synthesized,and the photophysical and electrochemical properties of these molecules were characterized by ultraviolet(UV-Vis)and cyclic voltammetry(CV),and the relevant parameters were calculated and analyzed.The results showed that NDI-N,NDI-NH and NDI-NN all had high solubility in commonly used organic solvents,and were easy to process and spin coating into films.The lowest unoccupied orbitals(LUMO)of the three molecules of NDI-N,NDI-NH and ndi-NN were obtained by ultraviolet absorption edge and cyclic voltammetry redox potential,which were-3.49,-3.76 and-3.86 e V,respectively,and the highest occupied orbital(HOMO)energy levels were-5.40,-6.44 and-5.74 e V,respectively,among which the conduction band(-3.80)of NDI-NH,NDI-NN and typical perovskite materials(CH3NH3Pb I3)were obtained e V)matches the valence band(-5.40 e V).The NDI-N,NDI-N,and NDI-NN molecules were filmed by solution spin-coating as a single-layer electron transport layer(ETL),and the structure was constructed as ITO/Ni Ox/MAPb I3-x Clx/ETL/Ag reverse planar perovskite solar cell devices,and the photoelectric conversion efficiencies of 8.58%,5.91% and 7.77%were initially obtained,respectively.Synthesis and device application of naphthimide-bithiophene small molecule electron transport materials Three small molecule electron transport materials based on naphthimide-bithiophene NDI-OL,NDI-NH-OL and NDI-NN-OL were designed and synthesized.The NDI-NN-OL and NDI-OL small molecules were characterized by ultraviolet(UV-Vis)and cyclic voltammetry(CV),and the LUMO and HOMO energy levels of NDI-NN-OL molecules were calculated to be-4.26 and-5.95 e V,respectively,while the LUMO and HOMO energy levels of NDI-OL were-4.5 e V and-6.34 e V.The NDI-NN-OL molecular energy level is more closely matched to the conduction band(-3.80 e V)and valence band(-5.40 e V)of typical perovskite CH3NH3 Pb I3,which can effectively transport perovskite layer electrons and block holes.The NDI-NN-OL molecules were filmed by solution spin-coating and used as a single-layer electron transport layer to construct planar trans-ITO/Ni Ox/MAPb I3-x Clx/ETL/Ag perovskite solar cell devices,and a photoelectric conversion efficiency of 5.99% was initially achieved. |
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