Elsevier

Optical Materials

Volume 109, November 2020, 110198
Optical Materials

High stability photosensitizers for dye-sensitized solar cells: Synthesis, characterization and optical performance

https://doi.org/10.1016/j.optmat.2020.110198Get rights and content

Highlights

  • Six new metal free organic dyes with D-π-A structure were synthesized.

  • Use of thioindoxyl as well as a stable light fast base.

  • Two types of TiO2 and ZnO nanopartical were used to prepare of photoanode.

  • The highest photocurrent was achieved for individual DSSC based on Dye contain thioindigo and cyanoacrylic acid.

Abstract

The output of various donating substituents on the optical behavior of new photosensitizers in the solar cells was investigated. The pure intermediates and dyes were identified via an analytical procedure and confirmed the chemical structure. Zinc oxide and titanium dioxide were operated to fabricate the nanocrystalline layer of the solar cells. The UV–Visible spectra of all synthesized dyes on ZnO and TiO2 illustrated blue shift due to the J-aggregation of organic dyes on the semiconductor substrate. To predict the usability of dyes in the structure of the solar cells, two methods, DFT and CV were employed. Finally, the DSSCs devices were prepared based on synthesized dyes and ZnO or TiO2. The highest photocurrent was achieved for individual device-TiO2 sensitized with Dye 2 containing thioindigo and cyanoacrylic acid. The operation of photovoltaic device based on zinc oxide was lower than that of titanium dioxide.

Introduction

The progressive rise in energy needs and environmental interest have caused a focus on the production and development of green sources of energy [1]. The permanent and environmentally friendly solar energy is the best alternative for this purpose [2]. Electric green energy is generated in solar cells using sunlight. In this regard, the third generation of technology includes: BHJ, DSSCs, and perovskite solar cells [3,4]. Considerable research has been done on the DSSCs to optimize the efficiency and durability [5]. One of the major components of the DSSCs is photosensitizers (dyes), which have a direct impact on efficiency and durability. Thus, many studies have focused on developing an optimal metal-free structures [6,7].

Four new organic dyes based on born dipyrromethene as photosensitizers were synthesized by Zhang. These dyes were engineered using various triarylamine groups. The DSSC's performance prepared by these dyes was studied, where the highest efficiency was achieved as about 4.42% for these devices [8]. Elsewhere, four fluorescent sensitizers for DSSCs were prepared by Hosseinezhad and Rouhani. These dyes were prepared using D-π-A structure employing iminobenzyl and cyanoacrylic acid as π-conjugated bridge and electron groups, respectively. Incorporation of two heterocyclic substituents in Dye 4 resulted in the highest efficiency of about 5% [9]. Al-horaibi et al. [10] prepared two new squarine sensitizers based indoline for DSSCs devices. The theoretical studies indicated that both dyes are suitable for DSSCs preparation. To study the effect of reducing the aggregation of dyes on a nano layer, various concentrations of anti-aggregation were applied in the preparation of solar cells. The solar cell contain anti-aggregation agent showed the highest yield. Some new organic sensitizers were designed by methylcarbazole derivatives and cyanoacetic acid as donor and acceptor groups, respectively. All dyes with small molecular weight had a planar structure. The DFT results showed that these dyes had a good performance in photovoltaic devices [11]. Hosseinnezhad et al. [12] synthesized two new dye as photosensitizers for three different orders of solar cells. The devices showed good photovoltaic performances about of 3–7%.

Here, the effect of various donating substituents was investigated on the photovoltaic performance of new photosensitizers (6 new dyes, Fig. 1) in the solar cells. The photosensitizers were refined and analyzed. The absorption behavior of all dyes in solution and applied on nano substrate were investigated. Then, dye sensitized solar cells were fabricated by these photosensitizers and DSSCs's optical properties were investigated.

Section snippets

Materials

All solvents and chemicals were sourced from Merck Company and consumed without refinements. The route of synthesis and characterization of component 1 have been described in the literature [13]. The raw materials for production of solar cells, including FTO, paste, electrolyte, and N719 were procured by the Sharif Solar Company. The FTIR, NMR, and absorption tests were done by PerkinElmer, 500 MHz Joel and Cecil 9200 double beam instrument, respectively.

Synthesis of 2-thiophene thioindoxyl (2)

To 0.194 mmol of [Pd(PPh3)4] was

Synthesis of dyes

The route of photosensitizer's synthesis was illustrated in Fig. 1. 2-Bromothiophene was commercially available as a raw material. This component reacted with bromothioindoxyl to give 2-thiophene thioindoxyl. The carbon-carbon bonding between two aromatic nuclei was prepared using Ullman coupling reaction [4]. 2-thiophene thioindigo reacted with n-BuLi/BuSnCl2 in THF media, with the reaction being followed by adding 5′-iodo-2,2′-bithiophene-5-carbaldehyde in the presence of (pph3)2pdCl2 as

Conclusion

Six organic photosensitizers containing different anchoring groups were engineered and prepared for DSSCs. The analytical methods were employed to identify organic dyes. Zinc oxide and titanium dioxide were operated to fabricate the nanocrystalline layer of the solar cells. The blue shift was observed in the UV–Visible test of the coated dyes on nanoparticles due to the J-type aggregation. The CV results showed that all synthesized dyes can transfer the excited electron to the photoelectrode

CRediT authorship contribution statement

Mozhgan Hosseinnezhad: Writing - original draft, Conceptualization, Visualization, Writing - review & editing, Project administration.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The authors sincerely thank the Center of Excellence for Color Science and Technology for making this investigation possible.

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