Triphenylamine Groups Improve Blocking Behavior of Phenoxazine Dyes in Cobalt‐Electrolyte‐Based Dye‐Sensitized Solar Cells

Abstract

Novel phenoxazine dyes are successfully introduced as sensitizers into dye-sensitized solar cells (DSCs) with cobalt-based electrolyte. In sensitizers with triphenylamine (TPA) groups recombination from electrons in the TiO2 conduction band to the cobalt(III) species is suppressed. The effect of the steric properties of the phenoxazine sensitizers on the overall device performance and on recombination and regeneration processes is compared. Optimized DSCs sensitized with IB2 having two TPA groups in combination with tris(2,2'-bipyridyl) cobalt(II/III) yield efficiencies of 6.3%, similar to that of IB3, which is equipped with mutiple alkoxy groups. TH310 with only one TPA group gives lower efficiency and open circuit voltage, while IB1 without TPA groups performs even worse. These results demonstrate that both TPA groups on the IB2 are needed for an efficient blocking effect. These results reveal a possible new role for TPA units in DSC sensitizer design.

Effect of conjugated side groups on the photovoltaic performances of triphenylamine-based dyes sensitized solar cells

“…The PCEs of POZ-based dyes have achieved 7-8% [23][24][25]. It is a good method to modify the structures of the π-bridges at the molecular level to optimize the properties of organic dyes [26][27][28].…”

Peripheral Hole Acceptor Moieties on an Organic Dye Improve Dye‐Sensitized Solar Cell Performance

“…Such a blocking effect of TPA groups was also recently observed for a series of phenoxazinebased dyes. [ 15 ] Charge extraction measurements (Figure 9 b) were performed to assess the effect of the sensitizer on the energy levels of the mesoporous TiO 2 electrode. Since no signifi cant difference is found, it may be assumed that the conduction band edge position of TiO 2 is not changed when sensitized with either D49 or E6 dye.…”

“…Furthermore, we found that additional TPA groups on the donor part of a D-π-A dye gave good blocking effect on sensitizer. [ 12,15 ] Herein we design the synthesis and describe the utilization of a modifi ed triphenylamine (TPA) dye named E6 in which two external TPA donors via insulating aliphatic chains are introduced into donor part, in comparison to the parent dye molecule D49 , see Figure 1 . After photoinduced electron injection, positive charge from the center TPA group in E6 will move to an outer TPA unit, which will lead the charge further away from the TiO 2 surface.…”

Effects of Structural Modification on the Photoelectrical Properties of the D‐A‐π‐A‐Type Dyes in DSSCs: A Computational Investigation

“…In recent decades, abundant dyes with D‐π‐A configuration have been successfully designed and synthesized by the researchers . Haid et al .…”