Synthesis Of Spiro Type Hole-transporting Materials With Linear Structure And Their Applications

Among many new clean energy,the Perovskite Solar Cells(PSCs)have attracted much attention in the field of solar energy after more than decades of research,and their Photoelectric Conversion Efficiency(PCE)had exceeded over 25%.Hole-Transporting material(HTM)is an important part of PSCs,Spiro-OMe TAD,as the most widely used HTM,has defects such as high cost and poor stability,which makes it difficult to carry out commercial application.Therefore,developing new HTMs to replace spiro-OMe TAD is the goal of researchers.The central core of spiro HTM is three-dimensional symmetrical structure,with poor molecular stacking and low hole-mobility.Doping is needed to improve its hole transport performance,but the use of dopant will degrade the accelerator.Therefore,the development of new spiro HTMs is of great significance for the preparation of stable and efficient PSCs.In this thesis,linear structure was introduced into spiro compounds.Through the regulation of molecular linear structure and spiro structure,two kinds of linear spiro HTMs were designed,synthesized and studied.Firstly,taking diarylamine substituted spirofluorene as the central core,four linear spiro molecules(Q11,Q12,Q01-1 and Q01-2)were constructed by introducing thiophene and its derivative conjugate groups.These molecules contain diarylamine substituted spirofluorene,which have large rigid structure,high hole-mobility and film-forming property,which can be used in doped devices;Through a series of tests,by introducing thiophene conjugated units with linear structure,the hole-mobility of HTMs is significantly improved,which are higher than Spiro-OMe TAD,and have good film-forming property.Among them,Q01-1 with nitrogen pyrrolothiophene(DTP)as conjugated unit performs best;After using hole molecules to prepare PSCs with ITO/Sn O₂/KCl/PVSK/HTM/Au structure,the doped device based on Q01-1 has the highest PCE of 19.14%,which is higher than Spiro-OMe TAD(18.57%)in the same batch;After the device stability test,the stability performance of doped devices based on Q01-1 is also better than Spiro-OMe TAD.Secondly,two linear spiro molecules Q20 and Q21 were constructed with linear thiophene-3,4-ethylene dioxythiophene(EDOT)-thiophene as the central core and dimethylfluorene substituted aromatic amine and spirofluorene oxaanthracene(SFX)substituted aromatic amine as the power supply group,respectively.In this kind of molecules,the spiro rigid structure is lower,and the linearity of the central core thiophene-EDOT-thiophene is higher.Therefore,this molecule has high intrinsic hole-mobility and can be used in dopant-free devices.In this paper,the effect of peripheral aromatic amines on molecular hole transporting performance was studied.The optimum PCE of the doping-free device based on Q21 is 17.60%,which is close to Spiro-OMe TAD under doped conditions;After being tested in 1000 h natural environment,200 h heating condition and 200 h illumination condition respectively,the doping-free device based on Q21 can still maintain more than 90%,80%and 95%of the initial PCE,showing very great device stability;By adjusting the rigid spiro and linear structure,this paper explored the combination of linear structure and spiro structure to construct a new type of organic small molecule hole-transporting materials,which provided a rich theoretical and data basis for the design of stable and efficient spiro hole-transporting materials.