Molecular Engineering Of Phenothiazine-based Hole Transport Materials And Their Application In Perovskite Solar Cells

The excellent photovoltaic performance and economic cost-effectiveness make perovskite solar cells(PSC)one of the most promising innovative photovoltaic technology for the future.As an important component in efficient PSC,hole transport materials(HTM)play a non-negligible role in the photoelectric conversion process by extracting and transporting photogenerated holes.However,the complex synthesis steps,high cost and poor stability of conventional HTM 2,2’,7,7’-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9’-spirobifluorene(Spiro-OMe TAD)are unfavorable for the commercialization of PSC.Therefore,the development of novel low cost and highly efficient HTM is of great importance for the preparation of efficient and stable PSC.In this thesis,we aimed to design and develop low-cost and highiy efficient HTM,through molecular engineering,a series of phenothiazine-based organic small molecules HTM are synthesized by carefully modulating the core backbone and peripheral substituents of HTM.The effects of molecular structure differences on the physicochemical properties and photovoltaic performance of HTM were systematically investigated.The detailed contents are listed below:1.Two phenothiazine-based HTM PTZT and D-PTZT in monomeric and dimeric configurations are designed and synthesized.It’s found that the dimer material D-PTZT has poor carrier transport efficiency due to the orthogonal conformation of the core unit,which weakens the intermolecular interactions;And the monomer PTZT exhibits excellent film formation and strong π-π stacking,which is more favorable for charge extraction and transport.The photovoltaic conversion efficiencies of 18.74% and 15.45% are obtained by applying PTZT and D-PTZT to the PSC,respectively.2.The HTM PTZT-MPF and PTZT-FF are further developed by molecular engineering optimization of the peripheral groups of PTZT using the fluorene substitution method.We found that the partial introduction of fluorene units can effectively improve the interfacial charge transfer ability of HTM and enhance the hydrophobicity of the films;The excessive introduction of fluorene units will lead to the aggregation of HTM in the thin film state,which is not conducive to the enhancement of device photovoltaic performance.The PTZT-MPF-based PSC achieves a20.15% photovoltaic conversion efficiency and better stability.3.HTM YT-PTPA,YT-KTPA and YT-KMPF are developed by replacing the core group as well as modulating the molecular conjugated bridge groups and peripheral substituents using DPTZT as reference material to investigate the effects of bridge groups and peripheral substituents on performance.It is shown that replacing phenothiazine with carbazole as the conjugated bridge group can significantly improve the structural planarity and charge delocalization of the molecule;the peripheral substituents mainly affect the film-forming and hydrophobic properties of the molecule.And the peripheral groups will affect the film-forming property and hydrophobicity of the molecule.After optimization,the high efficiency of 21.40% is obtained by applying YT-KMPF as the HTM of PSC.