N,N-Diarylanilinosquaraines and Their Application to Organic Photovoltaics

Abstract

We report new derivatives of symmetric squaraine dyes with N,N-diarylanilino substituents that have high solubility and high absorptivity (e = 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-Di...