Boosting Photoconductivity by Increasing the Structural Complexity of Multivariate Covalent Organic Frameworks

Abstract

The assessment of the photoconductivity of Donor-Acceptor (D-A) ordered bulk heterojunctions is gaining attention for the development of innovative organic semiconductors in optoelectronics. Here, the synthesis of pyrene-based (D) Covalent Organic Frameworks, achieve through a multivariate reaction involving two distinct acceptors is reported (A). The products are characterized using powder x-ray diffraction, N₂ sorption isotherms, electronic microscopy, and in silico calculations, among other techniques. These characterizations reveal that the multicomponent synthesis enables the modification of properties (e.g., bandgap) of the framework while preserving its structural features, such as crystallinity and porosity. The ordered D-A arrays position these materials as promising candidates for photoconductive semiconductors, particularly regarding the variation in the composition of isotopological frameworks. Photoconductivity experiments demonstrate a volcano-type correlation with respect to the A moiety content, with the optimal value reaching 7.9 × 10⁻⁵ cm² V⁻¹ s⁻¹ for the bare NIP_25%-COF. This study illustrates how introducing diverse acceptor units through multivariate synthesis can enhance the photoconductivity of these materials via “defect” engineering, without sacrificing their crystalline or porous characteristics and avoiding the need for de novo synthesis.