Optical Absorption Tailoring Enabled High‐Performance Dual‐Narrowband Organic Photodetectors for Secure Optical Communications

Organic photodetectors (OPDs) are distinguished by their tunable optoelectronic properties, being ideal for cutting‐edge light detection applications. Here, a game‐changing advancement is unveiled: a filter‐free dual‐narrowband OPDs creates through an Optical Absorption Tailoring (OAT) strategy that employs asymmetric vertical phase segregation of the photoactive layer to regulate its optical field distribution, thus achieving remarkable precision and reliability for light detection at specified wavelengths. With this strategy, the OPD exhibits a high dual‐narrowband response at 430 and 1070 nm without additional bias or filters, with enhanced D * over 10 12 Jones and J d (0 V) as low as 7.0 × 10 −10 A cm −2 , using commercially available material systems. The operational principles of the dual‐narrowband OPDs are investigated through optical and electrical simulations and charge transport dynamics analysis. It is discovered that the asymmetric segregation of components within the device not only consumes photons with relatively short wavelengths, which facilitates narrowband response at the near‐infrared cut‐off edge of the active layer, but also significantly suppresses the generation of dark current. A multitude of applications of narrowband OPDs are demonstrated, including health monitoring, image sensing, and encrypted optical communication, paving the way for the future development of novel and personalized technologies.