Crosstalk‐Free Dual‐Band Detection of Visible and Near‐Infrared Light Enabled by the Combination of Optical Design and One‐Step Transfer Printing

Abstract Eliminating optical crosstalk in multi‐band photodetectors is crucial for effective signal differentiation across wavelengths, particularly in optical communication and bioimaging applications. This study presents a strategy for achieving crosstalk‐free dual‐band organic photodetectors (OPDs) that integrate broadband visible and narrowband near‐infrared (NIR) detection. A back‐to‐back structure combining a visible detector and a NIR detector is employed using a one‐step transfer printing process. The front visible detector is designed for sensing visible photons, while the rear NIR detector is dedicated to detecting NIR photons. The transfer printing technique allows for an increased thickness of the rear NIR light‐absorbing layer, efficiently filtering out unwanted visible light. This design not only optimizes light distribution but also manipulates the charge collection, yielding a crosstalk‐free dual‐band OPD with peak responsivities of 115.0 mA W⁻¹ at 450 nm for visible detection and 85.5 mA W⁻¹ at 780 nm for NIR detection with a full width at half maximum of 47 nm. The device demonstrates robust performance in anti‐interference optical communication, accurately distinguishing target signals amidst multiple interferences. These findings pave the way for future advancements in optical crosstalk‐free multi‐band photodetector.