High-Performance Visible-Blind UV Phototransistors Based on n‑Type Naphthalene Diimide Nanomaterials

This study investigates
the performance of single-crystalline nanomaterials
of wide-band gap naphthalene diimide (NDI) derivatives with methylene-bridged
aromatic side chains. Such materials are found to be easily used as
high-performance, visible-blind near-UV light detectors. NDI single-crystalline
nanoribbons are assembled using a simple solution-based process (without
solvent-inclusion problems), which is then applied to organic phototransistors
(OPTs). Such OPTs exhibit excellent n-channel transistor characteristics,
including an average electron mobility of 1.7 cm2 V–1 s–1, sensitive UV detection properties
with a detection limit of ∼1 μW cm–2, millisecond-level responses, and detectivity as high as 1015 Jones, demonstrating the highly sensitive organic visible-blind
UV detectors. The high performance of our OPTs originates from the
large face-to-face π–π stacking area between the
NDI semiconducting cores, which is facilitated by methylene-bridged
aromatic side chains. Interestingly, NDI-based nanoribbon OPTs exhibit
a distinct visible-blind near-UV detection with an identical detection
limit, even under intense visible light illumination (for example,
104 times higher intensity than UV light intensity). Our
findings demonstrate that wide-band gap NDI-based nanomaterials are
highly promising for developing high-performance visible-blind UV
photodetectors. Such photodetectors could potentially be used for
various applications including environmental and health-monitoring
systems.