Study On The Linking Donor Dyes As Photosensitizers For Dye-Sensitized Solar Cells

In this thesis,two series of the linking donor dyes have been designed and synthesized as sensitizers for the application in the dye-sensitized nanocrystalline solar cell(DSSC).The linking donor are dimethylamine-triphenylamine and carbazole(triphenylamine)-carbazole. The structures of the dyes have been characterized by mass spectra(MS)and proton nuclear magnetic resonance(1H NMR)technology.The photophysical,photoelectrocheimical properties and the performance on DSSC of the dyes are studied.Dimethylamine-triphenylamine dyes are used in DSSC.Under simulated AM 1.5 (100mW cm-2)irradiation,a solar energy-to-electricity conversion efficiency(η)of 2.06%is obtained based on N-TPA1 with introducing a dimethylamine moiety,which has an decrease 0.13%inη,compared with triphenylamine dye.Under the same experimental conditions, N-TPA2 givesηof 1.60%with introducing rhodanine-3-acetic acid as electron-withdrawing part.Dimethylamine will enhance aggregation of a dye on TiO₂ surface.Density functional theory(DFT)calculations are performed for geometry optimization.The LUMO electron density geometry distribution of N-TPA1 is located on the cyanoacrylic group which favour electron injection,but for N-TPA2 it is mainly concentrated on the rhodanine framework,and resulting in the position of LUMO isolated from the -COOH anchoring group due to the presence of the -CH₂- group.Consequently,the N-TPA2 dye prevents electrons from effectively injecting into the TiO₂ conduction band via the carboxyl group.This is an important reason for the photoelectro peoperties of N-TPA2 inferior to N-TPA1.Carbazole(triphenylamine)-carbazole dyes are used in DSSC.Under simulated AM 1.5 (100mW cm-2)irradiation,the highest IPCE value for DSSC based on TCB with introducing a triphenylamine moiety is 60%at 460 nm and the IPCE value is over 50%from 400 to 500 nm.TCB givesηof 2.47%,which is up to half of N719 measured in the similar condition. Density functional theory(DFT)calculations are conducted and prove that the position of the LUMO is close to the anchoring groups(-COOH)which can enhance the orbital overlap with the 3d orbitals of TiO₂ and favour electron injection.Compared to 0.65 V with I₃^-/I^-,an open-circuit voltage(V_oc)of 1.03 V is obtained for CCB dye-sensitized solar cell with Br₃^-/ Br^- electrolyte under the same conditions,which is the highest open-circuit voltage known currently.This series of dyes have narrow absorption spectra in the visible region,from 350 to 500 nm,resulting in the weak use of solar energy,which is an important reason for the photoelectro peoperties of the dyes inferior to N719.