title: Flexible Organic Phototransistor Array with Enhanced Responsivity via Metal-Ligand Charge Transfer.
abstract: Phototransistors based on organic photoactive materials combine tunable light absorption in the spectral region from ultraviolet to near-infrared with low-temperature processability over large areas on flexible substrates. However, they often exhibit low photoresponsivity because of low molar extinction coefficient of photoactive components. We report a simple, yet highly efficient solution method for enhancing the performance of organic phototransistors using ruthenium complex 1 (Ru-complex 1). An air-stable n-type organic semiconductor, N,N'-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI), has been deposited on a silicon wafer and a transparent polyimide (PI) substrate via thermal evaporation under vacuum. The BPE-PTCDI phototransistors functionalized with Ru-complex 1 exhibit ∼5000 times higher external quantum efficiency (EQE) than that of pristine BPE-PTCDI phototransistors, owing to the metal-ligand charge transfer (MLCT) from Ru-complex 1 to the active component of the device. In addition, a large 10 × 10 phototransistor array (2.5 × 2.5 cm(2)) has been prepared on a transparent PI substrate, showing distinct light mapping. The fabricated phototransistor array is highly flexible and twistable and works well under tensile and compressive strains. We believe that our simple method will pave a viable way for improvements in the photoresponsivity of organic semiconductors for applications in wearable organic optoelectronic devices.
authors.affiliation: School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST) , Ulju-gun, Ulsan 689-798, South Korea.
authors.forename: Xien
authors.initials: X
authors.lastname: Liu
authors.affiliation: School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST) , Ulju-gun, Ulsan 689-798, South Korea.|Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, South Korea.
authors.forename: Eun Kwang
authors.initials: EK
authors.lastname: Lee
authors.affiliation: School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST) , Ulju-gun, Ulsan 689-798, South Korea.|Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, South Korea.
authors.forename: Dong Yeong
authors.initials: DY
authors.lastname: Kim
authors.affiliation: School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST) , Ulju-gun, Ulsan 689-798, South Korea.|Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, South Korea.
authors.forename: Hojeong
authors.initials: H
authors.lastname: Yu
authors.affiliation: Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH) , Pohang, Gyeongbuk 790-784, South Korea.
authors.forename: Joon Hak
authors.initials: JH
authors.lastname: Oh
keywords: flexible electronics; metal−ligand charge transfer; organic field-effect transistor; organic phototransistor; photoresponsivity