Halogenated Alkoxythiophene Additives Enhance the Performance of Organic Photodetectors

Abstract Morphological optimization of the active layer is pivotal for achieving high‐performance organic photodetectors (OPDs). Capitalizing on the simplicity and efficacy of additive strategies, a series of halogenated alkoxythiophene derivatives (MT–X) are employed as additives to refine the morphology of bulk heterojunction active layers, thereby improving the detection capabilities of OPDs. Systematic simulations uncover that the incorporation of MT–X effectively modulates the aggregation of non‐fullerene acceptors during film formation, fostering favorable phase separation and molecular packing. In OPD devices based on the PM6:BTP‐eC9 system, the application of additives enables stable fibrous aggregates and high‐quality molecular crystallinity within the active layer. This morphological refinement significantly promotes charge generation and transfer. Moreover, MT–X reduces the trap density and recombination losses of devices, consequently achieving an improvement in photocurrent density and responsivity. Under 0 V bias, the addition of MT–Cl, MT–Br and MT–I significantly suppresses the dark current density, yielding specific detectivity of 1.91 × 10 ¹³ , 3.06 × 10 ¹³ , and 5.93 × 10 ¹³ Jones at 635 nm, respectively. Meanwhile, the additives enhance the linear dynamic range and response speed, endowing the OPDs with pronounced visible‐to‐near‐infrared sensing capabilities and substantial potential for practical applications. This work provides a simple and effective strategy for optimizing the morphology and performance in organic optoelectronic devices.