Zu-Sheng Huang

Phenothiazine-based dyes for efficient dye-sensitized solar cells

As an emerging photovoltaic technology, dye-sensitized solar cells (DSSCs) have attracted a great deal of academic and industrial interest due to their reasonably high power conversion efficiency, low material cost and facile fabrication process. Metal-free organic dyes, as one of the key components of DSSCs, play a pivotal role in light harvesting and electron injection. Among the various species of organic dyes, easily tunable 10H-phenothiazine-based dyes hold a large proportion. The electron-rich nitrogen and sulfur atoms render 10H-phenothiazine a stronger donor character than other amines, even better than triphenylamine, tetrahydroquinoline, carbazole and iminodibenzyl. On the other hand, the unique non-planar butterfly conformation of the 10H-phenothiazine ring can sufficiently suppress molecular aggregation and the formation of excimers. The positions N-10, C-3 and C-7 of the 10H-phenothiazine ring system can easily be furnished with electron-donating or electron-withdrawing groups. Thus, the structural features of 10H-phenothiazine-based dyes guarantee the fabrication of efficient DSSCs. Some 10H-phenothiazine-based dyes show high photovoltaic performance, even better than the commercial ruthenium complex (N719). This paper reviews the recent significant scientific progress in 10H-phenothiazine-based DSSCs and focuses especially on the relationship between the molecular structure and the photoelectric conversion properties.

Dithienopyrrolobenzothiadiazole-based organic dyes for efficient dye-sensitized solar cells

Four novel D–π–A metal-free organic dyes DTP1–4 containing a dithienopyrrolobenzothiadiazole (DTPBT) unit were synthesized and applied in dye-sensitized solar cells, where DTPBT was employed as a π-spacer for the first time. The photophysical, electrochemical and photovoltaic properties of the dyes were systematically investigated. The dyes DTP1–4 showed broad absorption spectra and high molar extinction coefficient, resulting in high light harvesting efficiency. In addition, the impacts of donors and the thiophene unit as an additional π-spacer were also studied. The results showed that the dye DTP4 with triphenylamine as the donor exhibited better photovoltaic performance than DTP1–3 with phenothiazine as the donor. The linking position of the thiophene unit to the DTPBT unit significantly influenced the photovoltaic performance. A power conversion efficiency of 7.55% with 1 mM CDCA as the co-adsorbent under simulated AM 1.5 G illumination was reached by the DSSC sensitized by the dye DTP4. These results indicate that the DTPBT-based organic dye is a promising candidate for efficient DSSCs.

Effect of the linkage location in double branched organic dyes on the photovoltaic performance of DSSCs

Two novel double branched D–π–A organic dyes (DB dyes) are synthesized to investigate the influence of the linkage location in DB dyes on the performance of dye-sensitized solar cells (DSSCs), where phenothiazine is introduced as a donor, thiophene–benzotriazole unit as the π-bridge and cyanoacrylic acid as the electron-acceptor. The photophysical, electrochemical and photovoltaic properties of the dyes are systematically investigated. The results show that the location of the linkage unit has a small effect on the physical and electrochemical properties of the dyes. However, when the dyes are applied in DSSCs, an obvious decline of short-circuit current (Jsc) and open-circuit voltage (Voc) is found by moving the linkage unit from the donor part to the π-bridge part. The DSSC based on the dye DB-D with the linkage unit in the donor obtains an overall power conversion efficiency of 6.13%, which is about 68% higher than that (3.65%) of the DSSC based on the dye DB-B with the linkage unit in the π-bridge. The DB-B based device exhibits a lower efficiency due to its serious aggregation and short electron lifetime. The results indicate that the linkage location of the dyes has a big effect on the performance of the DSSCs.

Preparation of manganese dioxide using Ag+ ions as an electrocatalyst

Abstract The production of manganese dioxide by the conventional electrolytic process is based on the direct oxidation of Mn 2+ ions on an anode in sulfuric acid solution. The process is complicated. A new method for the preparation of manganese dioxide has been reported recently by the authors. This method uses Ag + ions to electrocatalyze the anodic oxidation of Mn 2+ ions. To show the difficulty in the direct anodic oxidation of Mn 2+ ion and the electrocatalytic mechanism of Ag + ions, the anodic oxidation behaviour of Mn 2+ and Ag + ions and the electrocatalytic behaviour of Ag + ions on the anodic oxidation of Mn 2+ ion are studied using a rotating ring disc electrode, a.c. impedance and voltammetry techniques. Mn 3+ ion or MnO 2 will be formed when Mn 2+ ion is oxidized on an anode, as determined by the sulfuric acid concentration. Mn 2+ ion is oxidized on the surface with OH groups and some compounds with Mn 2+ or Mn 3+ are formed before Mn 3+ ions or MnO 2 are produced. This causes difficulties in the preparation of Mn 3+ ions or MnO 2 . Ag + ions can be oxidized easily on an anode to form Ag 2+ ions. In turn, Mn 2+ ions can be oxidized easily by the Ag 2+ ions. Thus, the anodic oxidation of Mn 2+ ions can be e electrocatalyzed by using Ag 2+ ions. This is a homogeneous electrocatalysis and allows MnO 2 to be prepared in a convenient process.

Correction: Phenothiazine-based dyes for efficient dye-sensitized solar cells

Correction for ‘Phenothiazine-based dyes for efficient dye-sensitized solar cells’ by Zu-Sheng Huang et al., J. Mater. Chem. C, 2016, 4, 2404–2426.