Highly Conjugated, Fused-Ring, Quadrupolar Organic Chromophores with Large Two-Photon Absorption Cross-Sections in the Near-Infrared
| Autor: | Wei Wang, Taylor G. Allen, Seth R. Marder, Sepehr Benis, Boyu Jia, Natalia Munera, Junxiang Zhang, Joseph W. Perry, David J. Hagan, Stephen Barlow, Xiaowei Zhan, Shuixing Dai, Tengfei Li, Eric W. Van Stryland |
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| Rok vydání: | 2020 |
| Předmět: |
010304 chemical physics
Organic solar cell Chemistry Analytical chemistry Chromophore 010402 general chemistry 01 natural sciences Two-photon absorption Acceptor Spectral line 0104 chemical sciences 0103 physical sciences Ultrafast laser spectroscopy Physical and Theoretical Chemistry Absorption (electromagnetic radiation) Spectroscopy |
| Zdroj: | The Journal of Physical Chemistry A. 124:4367-4378 |
| ISSN: | 1520-5215 1089-5639 |
| DOI: | 10.1021/acs.jpca.0c02572 |
| Popis: | 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 × 103 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 red-shifted 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 m2) suggest that, although ESA contributions are non-negligible, the effective response is predominantly instantaneous 2PA. |
| Databáze: | OpenAIRE |
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