Improving Process Compatibility of Multilayer Organic Fiber Photodetectors by Combining Coaxial Thermal Evaporation with Dip-Coating

Fiber photodetectors (FPDs) are promising candidates for wearable applications due to their flexibility, knittability, and full-angle detection. The current state-of-the-art FPDs based on inorganic photosensitive materials show drawbacks in mechanical flexibility. The organic FPDs (OFPDs) are superior, while the fabrication is limited by multi-layer process compatibility issues. Herein, a diode-type five-layer OFPD with Zn/ZnO/PBDB-T:ITIC-Th/MoO 3 /PEDOT:PSS structure is prepared by combining thermal evaporation with a successive dip-coating method. It is worth mentioning that the uniform coaxial MoO 3 interfacial layer is processed by the proposed fiber-compatible thermal evaporation technique, while the other functional layers are enabled by the solution-based dip-coating method. At the bias of −0.5 V, the optimized OFPD exhibits a dark current density of 8.46 × 10 −8 A cm −2 , a responsivity of 86.4 mA W −1 (@ 760 nm), and a specific detectivity of over 10 11 Jones in the visible range of 400–760 nm. Besides, the device displays a fast response speed of 0.44 and 0.14 ms for rise and fall time, showing the capability of full-angle detection. The device is demonstrated in photoplethysmography for real-time heart-rate monitoring, suggesting its potential for practical application in wearable electronics.