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[摘要]：We report new derivatives of symmetric squaraine dyes with N,N-diarylanilino substituents that have high solubility and high absorptivity (epsilon = 0.71-4.1 x 10(5) M(-1) cm(-1)) in the red solar spectral region (lambda(max) = 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 (lambda(max) = 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-diary/anilino 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 (phi(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 angstrom)/C(60) (400 angstrom)/BCP (100 angstrom)/Al (1000 angstrom), 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 V(oc) = 0.59 +/- 0.05 V, short-circuit current J(sc) = 5.58 +/- 0.16 mA/cm(2), fill factor FF = 0.56 +/- 0.03, and power conversion efficiency eta = 1.8 +/- 0.2% under 1 sun, AM1.5G simulated illumination, compared with bis(N,N-diphenylanilino)squaraine: V(oc) = 0.82 +/- 0.02 V, J(sc) = 6.71 +/- 0.10 rnA/cm(2), FF = 0.59 +/- 0.01, and eta = 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. |
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