| Solar energy as one of the renewable energies is clean, and could be used in most regions on the surface of Earth. Among those devices that can convert solar energy into electricity, polymer soalr cells and dye-sensitized solar cells (DSSCs) have attracted considerable attention because they are cost-effective and easy to produce. Porphyrins possess a strong absorption band at around 425nm, and weak Q-bands at around 600 nm. To match well with the solar spectrum, investigators have been aiming to red-shift the Soret-band and broaden the Q-bands of the spectra of the porphyrins. In this paper, we designed and synthesized polymers and orgnic dyes based on porphyrin and modified by benzothiadiazole and thiophenes applied in bulk hetero-junction soalr cells and DSSCs. The structures of the as-synthesized copolymers and organic dyes were confirmed by FT-IR,1H-NMR,13C-NMR, Element Analysis and MALDI-TOF. The photophysical, electrochemical and photovoltaic properties of the copolymers and organic dyes have been investigated by UV-visible spectra, PL spectra and cyclic voltammetry. At last, the photovoltaic performances of solar cells based on the as-synthesized copolymers and organic dyes were measured. The main results are as follows:1. We synthesized two novel low band gap conjugated copolymers P1 and P2, containing porphyrins, thiophenes and 2,1,3-benzothiadiazole (BTZ) moieties for bulk-heteroj unction solar cells. The thermal, optical, electrochemical, and photovoltaic properties of the two copolymers were examined. The study results showed that the introduction of BTZ moiety in the backbone of the porphyrin polymers could broaden the Soret band and Q-bands, lower the band gap of the porphyrin polymer. The bulk hetero-j unction solar cells were fabricated based on the blend of the copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) in a 1:2 weight ratio. The maximum power conversion efficiency of 0.91%was obtained by using P2 as the electron donor under the illumination of AM 1.5,100 mW-cm-2.2. Two novel porphyrin dyes (PMBTZ and PHBTZ) modified with alkyl-thiophene and 2,1,3-benzothiadiazole(BTZ) moieties were designed and synthesized. The optical and electrochemical properties were characterized by UV-visible, fluorescence spectroscopy and cyclic voltammetry. The study results showed that with the introduction of the low-band-gap chromophore onto the porphyrins, the absorption spectra of the two porphyrin dyes were broadened and red-shifted and the first oxidation potentials (Eox1) were altered to the negative significantly Under standard global AM 1.5 solar condition, the dye-sensitized solar cell (DSSC) based on the dye PMBTZ showed the best photovoltaic performance:a short-circuit photocurrent density (Jsc) of 14.11 mA-cm-2, an open-circuit photovoltage (Voc) of 0.59 V, and a fill factor (ff) of 0.66, corresponding to solar-to-electric power conversion efficiency (η) of 5.46%.3. Four porphyrin dyes (Zl, Z2, Z3 and Z4), incorporating multi-alkylthienyl appended porphyrins as the electron donor, the 2-cyanoacrylic acid as the electron acceptor, and differentπ-conjugated spacer, were synthesized. All the porphyrin dyes studied in this work exhibit red-shifted and broadened electronic spectra respect to the reference Pzn as expected. By the introduction of thienyl groups at the meso-positions, the energy level of Eox* (excited-state oxidation potentials) is significantly shifted to the positive compared with the reference Pzn without modified, thus indicating a decreased HOMO (highest unoccupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) gap. The highest power conversion efficiency of the four dyes based on DSSCs of Z2 reached efficiency of 5.71% under AM 1.5 G irradiation. |
PDF Full Text Request