Asymmetric π-Bridge Engineering of Cyclopentadithiophene Based Acceptor for Sensitive NIR Organic Photodetectors
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Phorodetector for near-infrared (NIR) light enables many applications in various applications as near-infrared (NIR) light sensing platforms.1 Current organic photodetectors suffer from not enough acceptors to absorb light in NIR region and show a low photoresponse and a detectivity due to large dark/noise currents. Herein, we control the π-bridge acceptors based on cyclopentadithiophene both symmetric and asymmetric. The newly synthesized ultra-NBG NFAs, namely COB, and CBT with optical bandgaps below 1.14 eV. The COB (asymmetric) shows a higher responsivity of 0.369A/W than 0.080 A/W of CBT (symmetric). Also, COB demonstrate a higher specific detectivity of 2.18 × 1011 cm Hz1/2 W−1 at −0.5 V bias at 1,050 nm. These values of responsivity and detectivity are very close to that of a commercial Si photodiode.2 This work provides important insight into the molecular engineering strategy for ultra-NBG NFAs, which facilitate achieving highly sensitive NIR OPDs. (1) H. Xu et al., Adv. Mater., 29, 1700975 (2017). (2) Hamamatsu. Datasheet.