All‐Hand‐Drawn Flexible UV–Vis–NIR Photodetectors Based on Histidine‐Doped MoS ₂ Quantum Dots

Abstract Photodetectors play a vital role in optical communications, sensing, and medical diagnostics by converting light into electrical signals. However, conventional PD fabrication typically requires complex procedures and costly equipment, limiting scalability and flexibility. In this study, a facile and cost‐effective approach is demonstrated for fabricating metal‐semiconductor‐metal (MSM) PDs using a hand‐drawn Ag/MoS 2 quantum dots (QDs)/Ag structure via a paintbrush method. The resulting devices exhibit photocurrent responses comparable to those fabricated through conventional techniques. To evaluate reliability, the electrodes and active layers are repeatedly removed and redrawn, yielding consistent and stable performance. Furthermore, the method is extended to fabricate PDs on flexible, biodegradable 3 m Post‐it papers. In addition, these devices maintained excellent photoresponse even after 300 mechanical bending cycles at different curvatures, demonstrating mechanical durability and substrate versatility. This work not only introduces a scalable and eco‐friendly fabrication strategy but also opens new avenues for flexible and disposable optoelectronic applications.