Carbazole–pyrene-based nonvolatile solid additive to modulate the electronic structures of photodynamic devices

Abstract

Modulating the nanostructures of the active layers of optoelectronic devices via various techniques is crucial for enhancing the performances of these devices. However, commonly used liquid additives pose challenges in ensuring device-to-device reproducibility due to their effects on polymer solubility and the restriction of kinetic dynamics during film formation. To address these challenges, designing and incorporating solid additives that are independent of dynamics yet possess properties conducive to efficient charge transport into morphology modulation are important. Herein, a novel small molecule (9-(heptadecan-9-yl)-3,6-bis(5-(pyren-1-yl) thiophen-2-yl)-9H-carbazole (Cb-Th-Py)) is synthesized by combining a carbazole derivative with pyrene in an A-D-A structure. The bulk-heterojunction (BHJ) PM6:Y6 comprising Cb-Th-Py exhibits a smooth morphology. Additionally, via energy-level regulation, a higher electron injection barrier at reverse bias is induced, contributing to effective reduction of dark current. Particularly, Cb-Th-Py demonstrates high miscibility with Y6, ensuring an efficient charge transport pathway via strengthened π–π stacking, leading to a dense BHJ surface. This improves the charge mobility, decreases the trap density, and enhances the photocurrent of BHJ in addition to considerably suppressing noise. These Cb-Th-Py BHJ-based devices offer a more reproducible and effective avenue for performance enhancement of optoelectronics. © 2024 Elsevier B.V.