Synthesis And Applications Of Novel Hole Transport Materials For Perovskite Solar Cells

The hole transport material is one of the most important organic electroluminescent materials,which could effectively improve the injection efficiency and the transmission efficiency of the holes in the devices,and has been widely used in organic electronic devices such as organic light-emitting diodes(OLED),organic solar cells,organic phtoconductor(OPC),organic field-effect transistors(OFETs),and so on.In recent yeas,organic-inorganic halide perovskite solar cells(PSCs)have attracted increasing attention due to their simple structure,easy preparation,higher molar extinction coefficient and open circuit voltage.Organic solid hole transport materials applied in perovskite-based solar cells,which not only improves the power conversion efficiency(PCE)but also enhances the cell stability.Distinctly,HTMs are now an indispensable integral part of PSCs.In order to further improve the performance of perovskite solar cells,seeking novel hole transporting materials has become a hot spot in this field.In this thesis,six kinds of HTMs including the triphenylamine derivatives,spiro-OMeTAD derivatives and carbazole-based derivatives were designed,synthesized,and utilized in perovskite solar cells.On the one hand,the reaction mechanisms were discussed and their structures and properties were characterized by proton nuclear magnetic resonance(1H NMR)echnology,UV,fluorescence and cyclic voltammetry.Moreover,the compounds show good solubility in common solvents.On the other hand,the photovoltaic performances of the PSCs were characterized by measuring the current-voltage(J-V)traces and the incident photon-to-current efficiencies(IPCE).The main tasks as follows:Ground and excited state time dependent DFT(TD-DFT)calculations were loaded at B3LYP/6-31G(d)levels.The calculation results illustrated that the highest occupied molecular orbital(HOMO)of all HTMs could match with the work function of double-mixed perovskite,which is suitable to the hole injection.The UV/vis absorption spectra of the six newly synthesized HTMs were recorded in DCM and they showed a intense absorption in the visible region.Cyclic voltammetry measurement showed that HOMO levels of these compounds were in the range of-5.20eV?-5.33 eV,which coincide well with the trends of experimental data.Moreover,the reaction of the compound on the electrode surface is reversible.The lifetime values increased in the order of ?p+SYN1<?P+PARA1<?P+2,4-spiro-OMeTAD<TP+3,4-spiro-OMeTAD<TP+spiro<?P+TDT-OMeTPA<TP+TTPA-OMeTPA<?Perovskite,which is in good agreement with the variation trend of photovoltaic efficiency.The perovskite solar cells with different HTMs were fabricated.The device with 2,4-spiro-OMeTAD shows the highest short-circuit current density JSC=21.57 mA/cm2.The device with SYN1 shows the highest open-circuit voltage Voc=1.01 V and leading to a PCE of 13.1%.Under the same optimal conditions,the devices based on SYN1 exhibits higher photoelectric conversion efficiency than that of spiro-OMeTAD(?=12.0%).The results show that using molecular engineering to develop new efficient HTMs with high hole mobility and high conductivity is a feasible strategy for the PSCs.