Jiaqiang Zhang

Influence of the antennas in starburst triphenylamine-based organic dye-sensitized solar cells: phenothiazine versus carbazole

A new starburst triphenylamine-based organic dye (WD-1) with phenothiazine units as antenna groups was designed and synthesized and the corresponding dye (WD-4) containing carbazole antennas for the purpose of comparison was also synthesized. They were successfully applied in dye-sensitized solar cells (DSSCs). The photophysical and electrochemical properties of the dyes were investigated by UV-vis spectrometry and cyclic voltammetry. Under standard global AM 1.5 solar conditions, the WD-1 sensitized solar cell gave a short circuit photocurrent density (Jsc) of 9.2 mA cm−2, an open circuit voltage (Voc) of 625 mV, a fill factor (ff) of 0.79, corresponding to an overall conversion efficiency η of 4.54%. Under the same conditions, the WD-4 sensitized cell gave a Jsc of 7.3 mA cm−2, an Voc of 603 mV, and a ff of 0.74, corresponding to an overall conversion efficiency of 3.26%. An increase in η of about 39% was obtained from WD-4 to WD-1. Our findings demonstrate that the introduction of phenothiazine units as antennas in triphenylamine-based dyes could improve photovoltaic performance compared with carbazole units as antennas in DSSCs.

Theoretical study of carbazole–triphenylamine-based dyes for dye-sensitized solar cells

Three carbazole-triphenylamine-based dyes (D1, D2, D3) are designed. The geometries, electronic structures, and electronic absorption spectra of these dyes are studied by DFT and TD-DFT. The calculated geometries indicate that these dyes are all noncoplanar, which can help to inhibit the close intermolecular π-π aggregation effectively. The LUMO and HOMO energy levels of these dyes can be ensuring positive effect on the process of electron injection and dye regeneration. The trend of the calculated HOMO-LUMO gaps nicely compares with the spectral data. The calculated results of these dyes demonstrate that these dyes can be used as potential sensitizers for TiO(2) nanocrystalline solar cells.

Theoretical investigation of phenothiazine–triphenylamine-based organic dyes with different π spacers for dye-sensitized solar cells

Three phenothiazine-triphenylamine-based organic dyes (CD-1, CD-2 and CD-3) are designed based on the dye WD-8. The geometries, electronic structures, and electronic absorption spectra of these dyes before and after binding to TiO2 are studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The calculated geometries indicate that these dyes show good steric hindrance effect which is advantage to inhibit the close intermolecular π-π aggregation effectively. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of these dyes could ensure positive effect on the process of electron injection and dye regeneration. The simulated spectra of CD-1∼3 show better absorption than that of WD-8 in the low energy zone. All the calculated results demonstrate that these dyes could be used as potential sensitizers for DSSCs and show better performances than WD-8.

Structure-property relationships in conjugated donor–acceptor systems functionalized with tetrathiafulvalene

The properties of two donor–acceptor compounds tetrathiafulvalene-acenaphtho[1,2-b] quinoxaline (1) and tetrathiafulvalene-3-nitro-acenaphtho[1,2-b]quinoxaline (2) have been investigated by solution-state studies (electrochemistry, absorption, self-assembly) and theoretical calculations (DFT, TD-DFT). The electrochemical studies indicate the nitro-substituted effect on their redox properties is negligible. Both compounds show effective intramolecular charge transfer (ICT) transitions in the UV-Visible range in solution. Compared with compound 1, compound 2 has a bathochromic shift in the absorption spectra, the λmax−ICT has been extended from 20 800 cm−1 to 19 700 cm−1 (480 nm to 507 nm). In addition, when the nitro group is employed, the self-assembly characteristics of the two compounds are substantially changed from ribbon-like nanostructures to root-like nanostructures. Density functional theory (DFT) calculations provide insights into their molecular geometries, electronic structures, and physico-chemical properties.

A novel self-healing electrochromic film based on a triphenylamine cross-linked polymer

The cracking of electrochromic materials due to aging or reiterative bending is a major problem which noticeably degrades the performance of electrochromic devices. In the present research, we successfully induced a triphenylamine derivative into furfuryl glycidyl ether, and further by a DA cross-linking polymerization reaction with maleimide (MA) to yield polymer DATPFMA. The color of the polymer film could be switched from faint yellow to green grey to dark blue. The observed coloration efficiency values of the polymer for the electrochromic process were 82.2 and 175.3 cm2 C−1 at 580 and 1060 nm, and the coloring and bleaching response times were 4.1 and 11.0 s, respectively. The self-healing process of the polymer film at 110 °C was observed by optical microscopy and the self-healing rate was about 80%. The results indicate that the polymer DATPFMA is a novel electrochromic material with noteworthy self-healing properties.