Synthesis and Characterization of Diethylphosphonate and Carboxylate-appended Iridium Complexes for the Application on Dye-Sensitized Solar Cells

Abstract

In this work, cyclometalated iridium(III) complexes were synthesized, presenting a general formula [Ir(ppy)2(N N)]PF6, where ppy=2‐phenylpyridine or 2‐(2,4‐difluorophenyl)pyridine and N N=4,4′‐bis(diethylphosphonate)‐2,2′‐bipyridine or 4,4′‐bis(carboxy)‐2,2′‐bipyridine. The complexes were characterized by 1H‐NMR, 13C‐NMR 31P‐NMR and UV‐Vis spectroscopy. The assembled Dye Sensitized Solar Cells were characterized by current versus potential curves and by photon‐to‐current conversion efficiency measurements. The complexes present intense absorption bands in the UV region (250–350 nm), which are assigned to symmetry allowed singlet 1LC ππ* transitions involving both phenylpyridyl and bipyridyl ligands. At longer wavelengths (350‐450 nm) the weaker absorption bands are related to transitions with mixed metal‐to‐ligand and ligand‐to‐ligand charge transfer character. Dye desorption measurements revealed that the phosphonate group provide a more stable anchoring than the carboxylate. The most efficient devices were obtained by using iridium complexes with carboxylate anchoring groups.

“Iridium effect” in cyclometalated iridium complexes for p-type dye sensitized solar cells

“…There has been a growing interest in iridium(III) complexes, because they exhibit unique photophysical properties [1][2][3][4] that make them particularly well-suited for applications as dyes in organic light emitting devices (OLEDs), [2,5] biological labelling agents, [6][7][8][9][10] oxygen sensors, [11][12][13] photocatalysts for hydrogen evolution, [14][15][16][17] dye sensitized solar cells (DSSC), [18][19][20][21][22][23][24][25][26][27][28][29] as well as for the development of molecular photoactive arrays to attain longlived charge separated states. [30,31] Over the past few years, some of us [23] and others [20,24,25] have developed iridium(III) cyclometalated complexes for applications in NiO based ptype dye sensitized solar cells (p-DSSCs) and dye sensitized photoelectrosynthetic solar cells (p-DSPECs).…”

Exploration of the Structural and Photophysical Characteristics of Mono- and Binuclear Ir(III) Cyclometalated Complexes for Optoelectronic Applications

“…Dye-sensitized solar cells (DSSCs), being one of the alternative sources of electricity generation, for example, has gained prominent uptake in its usage worldwide over the last two decades due to their easy panel fabrication and cost-effective production when compared to the silicon-based photovoltaic devices [4,5,6]. Despite recent development and investigations in the molecule-based Ir(III) cyclometallated complexes as photosensitizers for DSSCs, the poor energy conversion efficiency originates from low molar extinction coefficient and a narrow absorption spectrum at relatively high energy, unlike those found for Ru(II) complexes [7], the efficiency of photosensitizers made from Ir(III) complexes can be improved by introducing better light-absorbing ligands [8,9,10,11,12].…”