Synthesis And Photovoltaic Properties Of Triphenylamine-thiophene Based Hole Transport Molecules For Perovskite Solar Cells

Hole transport material（HTM）is a very important part of organic-inorganic hybrid perovskite solar cells（PSCs）.Due to its relatively simple synthesis,easy purification,low cost,relatively high photoelectric conversion efficiency and other advantages,organic small HTMs become a research focus in the field of organic optoelectronic materials.Therefore,this thesis is devoted to the design and synthesis of low cost,easy purification and high efficiency of organic small molecule hole material,and its application in perovskite solar cell devices so as to obtain higher photoelectric conversion efficiency.The main research work of this thesis is as follows:1.Triphenylthiophene compounds M101-108 were synthesized as doped hole materials by a series of organic chemical reactions.First the intermediates and final products were structurally characterized.The results show that the compounds synthesized are the correct compounds required.Second,the compounds M101-108 were characterized by photophysical and electrochemical tests.The results showed that the oligothiophene can increase the conjugation of the molecule,which leads to the red shift of the spectrum.At the same time,oligothiophenes have a good regulation on the energy level of the molecule.Finally,we focused on the study of compounds M101-104.The results show that with the increase of intermediate thiophene groups,the thermal stability of the molecule is enhanced,the hole mobility and conductivity are also increased,and the conductivity of compound M104 is up to 6.73×10^-4 S.cm^-1,the hole mobility of M103reached 1.63×10^-4 cm².V^-1.S^-1.As a consequence,M103 and M104 based PSCs achieve a photoelectric conversion efficiency up to 14.78%and 13.02%.In order to further study the photovoltaic performance of the battery device,we carried out IPCE,electrochemical impedance test and SEM test on the battery device.The results further demonstrate that the compounds M103 and M104,due to its good solubility,film-forming properties,high conductivity and hole mobility,these achieve better photovoltaic performance.In addition,this paper also investigated the effect of additives such as phosphoric acid and cobalt salts on the performance of PSCs.This provides a new idea and direction for the design of high efficiency and low cost organic small molecule holes in the future.The compounds M105-108,did not achieve good photovoltaic performance mainly due to poor stability.2)Based on the high planarity and high electron cloud density of spirofluorene（SFX）and azolylthiophene（DTP）,we designed and synthesized the compounds HW7-10 with SFX and DTP as the parent nucleus of the hole material,also structurally characterizing their intermediates and final products.PSCs based on HW7-10 show low efficiency due to the undesirable film formability as result of low solubility.3)HW1-5 featuring D-A structure have been synthesized through the C-C coupling,C-N coupling and other organic reactions.This type of compound could be employed as doped-free HTMs for PSCs since they have good conductivity and strong conjugation.HW1-3 uses the 3-ethyl rhodanine as the electron-withdrawing group,while HW4-5 uses the dicyano group as the electron-withdrawing group.Preliminary tests show that the photovoltaic device based on HW1-5 does not achieve the desired photovoltaic performance.Further exploration and research are need in order to improve the performance of these HTMs.