Atto-Scale Noise Near-Infrared Organic Photodetectors Enabled by Controlling Interfacial Energetic Offset through Enhanced Anchoring Ability

The near-infrared (NIR) sensor technology is crucial for various applications such as autonomous driving and biometric tracking. Silicon photodetectors (SiPDs) are widely used in NIR applications; however, their scalability is limited by their crystalline properties. Organic photodetectors (OPDs) have attracted attention for NIR applications owing to their scalability, low-temperature processing, and notably low dark current density (J_D), which is similar to that of SiPDs. However, the still high J_D (at NIR band) and few measurements of noise equivalent powers (NEPs) pose challenges for accurate performance comparisons. This study addresses these issues by quantitatively characterizing the performance matrix and J_D generation mechanism using electron-blocking layers (EBLs) in OPDs. The energy offset at an EBL/photosensitive layer interface determines the thermal activation energy and directly affects J_D. A newly synthesized EBL (3PAFBr) substantially enhances the interfacial energy barrier by forming a homogeneous contact owing to the improved anchoring ability of 3PAFBr. As a result, the OPD with 3PAFBr yields a noise current of 852 aA (J_D = 12.3 fA cm⁻² at V → −0.1 V) and several femtowatt-scale NEPs. As far as it is known, this is an ultralow of J_D in NIR OPDs. This emphasizes the necessity for quantitative performance characterization.