Ralf Haiges - N,N-diarylanilinosquaraines and their application to organic photovoltaics.

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      Publication Details (including relevant citation   information): Wang, Siyi, Hall, Lincoln, Diev,   Vyacheslav V., Haiges, Ralf, Wei, Guodan, Xiao, Xin, Djurovich,   Peter I., Forrest, Stephen R., Thompson, Mark E., Chem.   Mater., 2011, 23 (21), pp   4789-4798

      Abstract: We report new derivs. of sym.   squaraine dyes with N,N-diarylanilino substituents that have high   soly. and high absorptivity (ε = 0.71-4.1 × 105 M-1 cm-1) in the   red solar spectral region (λmax = 645-694 nm) making them   promising candidates for application in org. photovoltaics   (OPVs). Unsym. N,N-diisobutylanilino- and   N,N-diphenylanilino(diphenylamino)squaraines have also been   prepd. that give blue-shifted absorption spectra (λmax = 529-535   nm) relative to their sym. counterparts. Compared to   bis(N,N-diisobutylanilino)squaraine, both sym. and unsym.   N,N-diarylanilino squaraines show markedly broader absorption   bands in soln. than their N,N-dialkylanilino squaraine   counterparts: the full width at half-max. (fwhm) for   N,N-diarylanilino squaraines range from 1280-1980 cm-1, while the   fwhm value for the N,N-diisobutylanilino squarine is only 630   cm-1. The absorption bands for thin films of N,N-diarylanilino   squaraines broaden further to 2500-3300 cm-1. N,N-Diarylanilino   squaraines are fluorescent, albeit with lower quantum yields than   bis(N,N-diisobutylanilino)squaraine (ϕPL = 0.02-0.66 and 0.80,   resp.). OPVs were prepd. with soln. processed squaraine layers   using the following structure: ITO/squaraine (66-85 Å)/C60 (400   Å)/BCP (100 Å)/Al (1000 Å), BCP = bathocuproine. Devices using   thin films of the bis(N,N-diarylanilino)squaraines as donor   layers show improved performance relative to OPVs prepd. with   bis(N,N-dialkylanilino)squaraines, i.e.   bis(N,N-diisobutylanilino)squaraine: open-circuit voltage Voc =   0.59 ± 0.05 V, short-circuit current Jsc = 5.58 ± 0.16 mA/cm2,   fill factor FF = 0.56 ± 0.03, and power conversion efficiency η =   1.8 ± 0.2% under 1 sun, AM1.5G simulated illumination, compared   with bis(N,N-diphenylanilino)squaraine: Voc = 0.82 ± 0.02 V, Jsc   = 6.71 ± 0.10 mA/cm2, FF = 0.59 ± 0.01, and η = 3.2 ± 0.1%.   Morphol. studies of thin films suggest that the soly. of   bis(N,N-diarylanilino)squaraines plays an important role in   controlling the optoelectronic properties of the OPVs. [on   SciFinder(R)]

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