Near Infrared Light‐Sensing Organic Light‐Dependent Resistors Based on Dialkoxybenzothiadiazole‐Containing Conjugated Polymer

• Published in: Physica status solidi. A, Applications and materials science Vol. 219; no. 9
• Main Authors: Cho, Yeonhwa, Lee, Saebom, Kim, Taehoon, Kim, Hwajeong, Song, Dong-Ik, Kim, Youngkyoo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.05.2022
• Subjects: electrical resistance; Glass transition temperature; Lidar; Light; Luminous intensity; near infrared organic light-dependent resistors; Near infrared radiation; Photoelectric effect; photoresistors; Polymers; Resistors; Semiconductor lasers; semitransparent devices; Thermal stability
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202200068

Herein, near infrared light‐sensing organic light‐dependent resistors (NIR–OLDRs) is reported, that are fabricated with a planar geometry by employing poly[{3‐(5‐(7‐methyl‐5,6‐bis(octyloxy)benzo[c][1,2,5]thiadiazol‐4‐yl)thiophen‐2‐yl)‐6‐(5‐methylthiophen‐2‐yl)}‐co‐{2,5‐bis(2‐octyldodecyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione}] (PDPP‐8OBT) as an active layer. The PDPP‐8OBT polymer, which is synthesized by the Stille coupling reaction of corresponding monomers, shows a broad absorption up to ≈1000 nm (wavelength) and good thermal stability with a glass transition temperature of >200 °C. A high‐power laser diode, which emits a monochromatic NIR light (wavelength = 905 nm) for light detection and ranging (LiDAR) systems, is used to examine the characteristics of NIR–OLDRs. Results show that the present NIR–OLDRs can successfully detect the 905 nm NIR light and their electrical resistance (and photocurrent) is sensitive to the incident intensity of NIR light. In particular, for both regular and semitransparent devices, the best NIR light‐sensing performances are achieved by device annealing at 150 °C (change of resistance = 34.5%) due to the increased crystallinity of PDPP‐8OBT films. The present NIR–OLDRs exhibit excellent sensing stability upon optical on/off modulations of NIR light (905 nm). Herein, the poly[{3‐(5‐(7‐methyl‐5,6‐bis (octyloxy)benzo[c][1,2,5]thiadiazol‐4‐yl)thiophen‐2‐yl)‐6‐(5‐methylthiophen‐2‐yl)}‐co‐{2,5‐bis(2‐octyldodecyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione}] (PDPP‐8OBT) polymer is synthesized via Stille coupling reaction, and its films are applied as an active layer for near infrared light‐sensing organic light‐dependent resistors (NIR–OLDRs). The NIR‐OLDRs with the thin (for semitransparent devices) and thick PDPP–8OBT films annealed at 150 °C can detect the 905 nm light used for light detection and ranging (LiDAR) systems.