Novel Red Light-Absorbing Organic Dyes Based on Indolo[3,2-b]carbazole as the Donor Applied in Co-Sensitizer-Free Dye-Sensitized Solar Cells.

Zhanhai Xiao,Bing Chen,Xudong Cheng

doi:10.3390/ma14071716

Abstract

Three novel organic dyes (D6, D7 and D8), based on indolo[3,2-b]carbazole as the donor and different types of electron-withdrawing groups as the acceptors, were synthesized and successfully applied in dye-sensitized solar cells (DSSCs). Their molecular structures were fully characterized by 1H NMR, 13C NMR and mass spectroscopy. The density functional theory (DFT) calculations, electrochemical impedance spectroscopy analysis, UV–Vis absorption characterization and tests of the solar cells were used to investigate the photophysical/electrochemical properties as well as DSSCs’ performances based on the dyes. Dye D8 showed the broadest light-response range (300–770 nm) in the incident monochromatic photo-to-electron conversion efficiency (IPCE) curve, due to its narrow bandgap (1.95 eV). However, dye D6 exhibited the best device performance among the three dyes, with power conversion efficiency of 5.41%, Jsc of 12.55 mA cm−2, Voc of 745 mV and fill factor (FF) of 0.59. We also found that dye aggregation was efficiently suppressed by the introduction of alkylated indolo[3,2-b]carbazole, and, hence, better power conversion efficiencies were observed for all the three dyes, compared to the devices of co-sensitization with chenodeoxycholic acid (CDCA). It was unnecessary to add adsorbents to suppress the dye aggregation.

Highlights

IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The systematic study of their photophysical and electrochains of indolo[3,2-b]carbazole, demonstrating better power conversion efficiencies (PCEs) even in the co-sensitizer-free chemical properties, as well as the resulting dye-sensitized solar cells (DSSCs) performances based on the three dyes, DSSCs
Dye D6, containing thiophene cyanoacetic acid acceptor, exhibits much higher ε and dye loading amount than the other two dyes, which indicates that dye D6 possesses better light-harvesting capability

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. DSSCs based on metal-free organic dyes have achieved a very high PCE of 14% [9]. Those dyes have complex structures and are difficult to synthesize. The dye aggregation was results show, of thedyes introduction of benzothiadiazole effectively expanded thesuppressed light absorption theto two of indolo[3,2-b]carbazole, demonstrating better PCE by even the alkyl of by dyes. The systematic study of their photophysical and electrochains of indolo[3,2-b]carbazole, demonstrating better PCE even in the co-sensitizer-free chemical properties, as well as the resulting DSSCs performances based on the three dyes, the systematic study of their photophysical and electrochemical properties, was reported.

Materials and Methods

Fabrication and Characterization of DSSCs

Synthesis

Photophysical

Theoretical Calculations

Conclusions