Weak Intermolecular Interaction-Dominated Photoelectric Performance in a p -Fluoranil (FA)-Based Organic Charge-Transfer Cocrystal Photodetector

Organic semiconductor-based photodetectors with the advantages of lightweight, convenient processing, flexibility of substrates, and adjustable absorption characteristics have garnered widespread attention. Organic charge-transfer cocrystals are one type of excellent candidate because the photoelectric performance can be regulated by the intermolecular weak interactions, such as π–π interactions, hydrogen bonds, halogen bonds, and charge-transfer interactions. In this work, two charge-transfer cocrystals, perylene–p-fluoranil (FA) and chrysene–FA, were grown by the slow-cooling method. The perylene–FA and chrysene–FA show comparable π–π interactions, while the chrysene–FA exhibits stronger hydrogen interactions. The degree of charge-transfer (DCT) of perylene–FA and chrysene–FA was determined to be 0.066 ± 0.003 and 0.054 ± 0.003 by Infrared (IR) spectra, respectively, while 0.155 ± 0.003 and 0.085 ± 0.003 by Raman spectra, respectively. Both perylene–FA and chrysene–FA photodetectors show a detection range from 300 to 780 nm. The perylene–FA photodetector exhibits the best responsivity (R) and specific detectivity (D*) values of 5.51 A·W–1 and 1.99 × 1011 Jones at 780 nm, respectively. In contrast, the chrysene–FA shows the best R and D* values of 3.69 A·W–1 and 6.80 × 1010 Jones at 635 nm, respectively. The larger DCT, the appropriate energy gap, and fewer defects of perylene–FA, rather than the hydrogen interactions and π–π interaction, may be responsible for the better optoelectrical performance. This work provides a potential approach for tuning the optoelectric performance of organic charge-transfer cocrystal-based photodetectors.