Novel branched coumarin dyes for dye-sensitized solar cells: significant improvement in photovoltaic performance by simple structure modification

Abstract

The construction of branched coumarin dyes based on a 2D-p-A system is focused to optimize the light-harvesting capability and enhance the photovoltaic performance. Three novel coumarin dyes, coded as MS-C, MS-F, and MS-M, respectively, were obtained by incorporating different units (carbazole, fluorene and methyl groups) with different molecular volume and degrees of electrondonating capability into the p-conjugation linker. Through molecular engineering, their lightharvesting capabilities, energy levels and photovoltaic performance were studied systematically. As expected, with the additional donor, especially utilizing strong electron-donating carbazole unit, the IPCE action spectrum of MS-C keeps a high plateau from 390 nm to 580 nm with nearly unity values. Along with the improvement of IPCE, the J sc values of the three dyes were increased by 77% from 7.61 (MS-M) to 13.47 mA cm À2 (MS-C). Using DCA as the co-adsorbed material, the J sc of MS-M was increased while these values were decreased in the cases of branched MS-C and MS-F. This means that the twist structure arising from the branched donors could prevent p-aggregation effectively. More importantly, the V oc was also improved significantly by introducing the additional donor. While the branched 2D-p-A system was constructed, the V oc was sharply increased from 508 (MS-M) to 610 mV (MS-C). Comprehensively, a more than 100% enhancement in overall conversion efficiency (5.53%) was realized by branched MS-C compared to the linear MS-M (2.74%). Although the overall conversion efficiencies of these dyes are not very high, these results will still afford significant value for future development of efficient coumarin sensitizers with high open-circuit voltage.

Review on polymer electrolyte in dye-sensitized solar cells (DSSCs)

“…Many different types of dyes have been extensively studied for DSSCs application and it can be classified into two main types; organic dyes and inorganic dyes according to the structure (Kong et al, 2007). Organic dyes include natural organic dyes such as coumarin (Hara et al, 2003a(Hara et al, , 2003bLiu et al, 2012), perylene (Cappel et al, 2009;Zafer et al, 2007) and synthetic dyes. While, inorganic complexes dyes includes metal complex, such as polypyridyl complexes of transition metals, metalloporphyrins, metallo-phathalocyanines and inorganic quantum dots (CdS, CdSe, CZTS, ZnTe) which has high thermal stability and chemical stability as compared to organic dyes (Giribabu and Kanaparthi, 2013;Hagfeldt et al, 2010;Kalyanasundaram and Grätzel, 2009;Yella et al, 2011).…”

AIE Based Coumarin Chromophore - Evaluation and Correlation Between Solvatochromism and Solvent Polarity Parameters

“…Coumarin constitute the largest class of laser dyes in the 'blue-green' region [21][22][23][24][25]. Coumarin dyes have also been used as blue, green and red dopants in organic light-emitting diodes (OLEDs) [26][27][28], in dye-sensitized solar cells (DSSC) [29][30][31] and tailored to in vivo imaging applications [32][33][34][35]. In recent years Wang and co-workers report AIE active coumarin-based Schiff bases and successively put into applications in cell imaging [36].…”

Novel coumarin sensitizers based on 2-(thiophen-2-yl)thiazole π-bridge for dye-sensitized solar cells

“…19 Since introduction of additional donor or acceptor is a better choice to optimize the absorption spectrum than a flexible extended πbridge, Kim reported novel D-A-π-A coumarin dye containing benzothiadiazole chromophore 20 and Yu et al synthesized branched coumarin dyes based on a 2D-π-A system to prevent π-aggregation and improve the photovoltaic performance. 21 However, those coumarin sensitizers feature the coumarin donors substituted by rigid nitrogen-containing cycle which are prepared through redundant synthetic process. In our previous work, we have reported several coumarin sensitizers characteristic of easily available 7-diethylamine coumarin donor.…”