Narrowband‐Absorption‐Type Organic Photodetectors for the Far‐Red Range Based on Fullerene‐Free Bulk Heterojunctions

Abstract Spectrally‐selective photodetection via organic semiconductors manifesting narrowband absorption (NBA photodetection) is highly attractive for emerging applications that require ultrathin, lightweight, and low‐cost solutions. While successful over mainstream color bands, NBA photodetectors have struggled so far to meet the functional and/or performance demands at longer wavelengths, importantly in the far‐red (700–750 nm), a range relevant to diverse applications in analytical biology, medical diagnostics, remote sensing, etc. In consideration of the potential of a nonfullerene‐acceptor route to address this challenge, the narrowband photodetection capabilities of SBDTIC, a recently‐developed benzodithiophene‐based acceptor with narrowband absorption in the far‐red, are explored. Two bulk‐heterojunction NBA configurations are considered, in which SBDTIC is combined with a donor either absorbing also in the far‐red, or transparent through the visible. It is found that the latter configuration provides superior narrowband functionality, with peak detectivity of 1.42 × 10¹³ Jones and spectral width of 141 nm—the highest detectivity to date for NBA far‐red‐selective photodetectors, and the smallest spectral width of all solution‐processed implementations. In self‐powered operation, such photodetectors additionally present a quasilinear response over a photocurrent range of least four orders of magnitude, and respond in the microsecond range, further evidencing the suitability of this approach to address the wealth of target applications.