1,2,5]Thiadiazolo[3,4-d]Pyridazine as an Internal Acceptor in the D-A-π-A Organic Sensitizers for Dye-Sensitized Solar Cells.

Chmovzh Chmovzh,Popov Popov,Knyazeva Knyazeva,Mikhalchenko Mikhalchenko,Rakitin Rakitin,Robertson Robertson,Mlv@Ioc.Ac.Ru Tanaka

doi:10.3390/molecules24081588

Abstract

Four new D-A-π-A metal-free organic sensitizers for dye-sensitized solar cells (DSSCs), with [1,2,5]thiadiazolo[3,4-d]pyridazine as internal acceptor, thiophene unit as π-spacer and cyanoacrylate as anchoring electron acceptor, have been synthesized. The donor moiety was introduced into [1,2,5]thiadiazolo[3,4-d]pyridazine by nucleophilic aromatic substitution and Suzuki cross-coupling reactions, allowing design of D-A-π-A sensitizers with the donor attached to the internal heterocyclic acceptor not only by the carbon atom, as it is in a majority of DSSCs, but by the nitrogen atom also. Although low values of power conversion efficiency (PCE) were found, a few important consequences were identified: (i) poor PCE data can be attributed to high electron deficiency of the internal [1,2,5]thiadiazolo[3,4-d]pyridazine acceptor due to lower light harvesting by the dye; (ii) the manner in which the donor was attached to the internal acceptor (by carbon or nitrogen) did not play an essential role in the photovoltaic properties of the dyes; (iii) dyes based on the novel donor 2,3,4,4a,9,9a-hexahydro-1H-1,4-methanocarbazolyl and 9-(p-tolyl)-2,3,4,4a,9,9a-hexahydro-1H- carbazole moieties showed similar photovoltaic properties to dyes based on the well-known 4-(p-tolyl)-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indolyl building block, which opens the door for further optimization potential of new dye families.

Highlights

In the recent years, solution processable solar cells, including dye-sensitized solar cells (DSSCs) [1,2,3,4], bulk heterojunction donor-acceptor blends [5,6], quantum dot solar cells [7,8], organic–inorganic hybrid perovskite solar cells [9,10,11], and tandem solar cells [12,13] have attracted much attention to in the search to produce low-cost electricity and portable energy
Compared to D-π-A dyes, D-A-π-A sensitizers, where the auxiliary acceptor is inserted between the donor and the π-bridge, showed broadened absorption, optimized energy levels, enhanced stability, and efficient intramolecular charge transfer for high performance DSSCs [23]
Taking into account the ease of introduction of N-nucleophiles into [1,2,5]thiadiazolo[3,4-d]pyridazine by nucleophilic aromatic substitution, we aimed to design and prepare D-A-π-A sensitizers with the donor attached to the internal heterocyclic acceptor by the carbon atom, as it is in a majority of DSSCs, but by the nitrogen atom

Summary

Introduction

Solution processable solar cells, including dye-sensitized solar cells (DSSCs) [1,2,3,4], bulk heterojunction donor-acceptor blends [5,6], quantum dot solar cells [7,8], organic–inorganic hybrid perovskite solar cells [9,10,11], and tandem solar cells [12,13] have attracted much attention to in the search to produce low-cost electricity and portable energy. DSSCs, as a new kind of green energy device, display important properties such as easy fabrication, relatively low production cost, low toxicity, and good flexibility of molecular design [14,15,16]. Compared to D-π-A dyes, D-A-π-A sensitizers, where the auxiliary acceptor is inserted between the donor and the π-bridge, showed broadened absorption, optimized energy levels, enhanced stability, and efficient intramolecular charge transfer for high performance DSSCs [23]. Some electron-withdrawing groups, such as diketopyrrolopyrrole [24], benzothiadiazole [25], selenadiazolopyridine [26], benzotriazole [27], quinoxaline [28], isoindigo [29], and many others, have been inserted into the D-A-π-A framework

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Conclusion