Highly Conjugated, Fused-Ring, Quadrupolar Organic Chromophores with Large Two-Photon Absorption Cross-Sections in the Near-Infrared

Abstract

The two-photon absorption (2PA) properties are investigated for two series of organic, π-conjugated, fused-ring, quadrupolar A-π-D-π-A chromophores of the type originally developed as nonfullerene acceptors for organic photovoltaics. These molecules are found to exhibit large nondegenerate two-photon absorption (ND2PA) cross-sections (ca. 6−27 × 10 3 GM) in the near-infrared (NIR). In the first series, involving molecules of varying core size, ND2PA spectra and cross-sections characterized by femtosecond ND2PA spectroscopy in chloroform solutions reveal that increases in core size, and thus conjugation length, leads to substantially redshifted and enhanced 2PA. In a second series, variation of the strength of the terminal acceptor (A) with constant core size (seven rings, indacene-based) led to less dramatic variation in the 2PA properties. Among the two core types studied, compounds in which the donor has a thieno[3,2-b]thiophene center demonstrate larger 2PA cross-sections than their indacene-centered counterparts, due to the greater electron-richness of their cores amplifying intramolecular charge transfer. Excited-state absorption (ESA) contributions to nonlinear absorption measured by open-aperture Z-scans are deduced for some of the compounds by analyzing the spectral overlap between 2PA bands and NIR ESA transitions obtained by ND2PA and transient absorption measurements, respectively. ESA cross-sections extracted from transient absorption and irradiance-dependent open-aperture Z-scans are in reasonable agreement, and their moderate magnitudes (ca. 10 −21 m 2 ) suggest that, although ESA contributions are non-negligible, the effective response is predominantly instantaneous 2PA.

Synthesis, Characterization, and Photophysical Properties of a New Indolizine Pyridine Complex with a Large Two‐Photon Absorption Cross‐Section

“…Comparing the β and δ of compound 1 with those reported earlier for organic compounds ( δ max =5180 GM, [27] δ max =6700 GM, [23] δ max =8100 GM, [22] δ max =17400 GM, [28] δ max =6∼27×10 3 GM [29] ), we find that the compound ( 1 ) has remarkable and very strong nonlinear optical absorption, and exhibit the very large TPA cross‐section. Compared with the three organic compounds with the largest two‐photon absorption cross‐section area reported in literature (their structures see SI on page S‐16∼S‐17) ), the structure of compound 1 reported in this paper is very simple, and the synthesis method is also very simple, which can be completed by one‐pot method.…”

“…2020, Taylor Allen et al . reported a series of highly conjugated, fused‐ring quadrupolar organic chromophores with large TPA cross‐sections (6000‐27000 GM) [29] . By comparing organic chromogenic groups reported above, we can see that organic compounds with A‐π‐D‐π‐A structure may have better TPA cross‐section than that of organic compounds with D‐π‐D, A‐π‐A, D‐π‐A or D‐π‐A‐π‐D structure (Scheme 1).…”

Near-infrared dyes for two-photon absorption in the short-wavelength infrared: strategies towards optical power limiting

“…In 2020, the latest works by Perry and Marder were dedicated to fused-ring quadrupoles introducing indacene and thieno [3,2b]thiophene electron-rich cores that show exceptionally strong 2PA due to the particularly efficient ICT. 234 Consequently, while cross-sections higher than 6000 GM are measured for the smallest compounds, the most extended quadrupoles 75 and 76 present huge values reaching 14000 and 27000 GM around 1345 nm.…”

Highly broadband NLO response of acceptor–donor–acceptor materials with a planar conformation

“…6-27×10 3 GM ) in the near-infrared region. 13 However, the study on NLO properties of A-D-A as mentioned above mainly focus on increasing the number of rings to modify conjugated length and changing terminal group to regulate the ICT. More factors, such as the influence of molecular conformation on NLO performance remain unknown.…”