Vyacheslav Diev - N,N-Diarylanilinosquaraines and their application to organic photovoltaics

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      Publication Details (including relevant citation   information):

      Chem.   Mater.   2011, 23, 4789-4798

      Abstract:

      We report new derivatives of symmetric squaraine dyes with   N,N-diarylanilino substituents that have high solubility   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 organic photovoltaics (OPVs). Unsymmetrical   N,N-diisobutylanilino- and   N,N-diphenylanilino(diphenylamino)squaraines have also been   prepared that give blue-shifted absorption spectra   (λmax = 529–535 nm) relative to their symmetric   counterparts. Compared to bis(N,N-diisobutylanilino)squaraine,   both symmetrical and unsymmetrical N,N-diarylanilino   squaraines show markedly broader absorption bands in solution   than their N,N-dialkylanilino squaraine counterparts:   the full width at half-maximum (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 (PL  = 0.02–0.66 and 0.80, respectively). OPVs were prepared with   solution 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 prepared 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%. Morphological   studies of thin films suggest that the solubility of   bis(N,N-diarylanilino)squaraines plays an important role   in controlling the optoelectronic properties of the OPVs.

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/cm2020803