Organic phototransistors based on solution grown, ordered single crystalline arrays of a π-conjugated molecule

다국어 초록 (Multilingual Abstract)

<P>High quality, single crystalline, ordered arrays of a π-conjugated organic molecule, <I>N,N′</I>-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C<SUB>8</SUB>), were grown by solution processing and used to fabricate a low-cost, high-performance organic phototransistor (OPT). The single crystalline nature of the microstructure was investigated using 2D-GIXD measurement. The organic field-effect transistor fabricated using periodic arrays of elongated crystals exhibited a photoresponsivity (<I>P</I>) of <I>ca.</I> 1 A W<SUP>−1</SUP> and a photo to dark current ratio (<I>I</I><SUB>on</SUB>/<I>I</I><SUB>off</SUB>) of 2.5 × 10<SUP>3</SUP> at <I>V</I><SUB>G</SUB> = 12 V and a maximum <I>P</I> of <I>ca.</I> 7 A W<SUP>−1</SUP> at the high gate bias regime (<I>V</I><SUB>G</SUB> = 50 V) with an optical power of <I>ca.</I> 7.5 mW cm<SUP>−2</SUP>. With polymeric gate dielectric, the OPT exhibited very stable n-type characteristics both in the dark and under light illumination and showed reproducible photo-switching behavior. The dependence of the photocurrent on the gate/drain voltage and on illumination intensity provided an effective way to control the number of photo-carriers generated in the active material, enabling the precise tuning of the device's performance. Performance comparison between OPTs with ordered crystal arrays and thin films of PTCDI-C<SUB>8</SUB> confirmed that the material's intrinsic properties were better realized in the crystalline device, presumably because of higher charge carrier mobility and better charge transport capability. This one-step, solution-based, self-assembly fabrication of multifunctional (photodetection, photoswitching, signal amplification) optoelectronic devices has potential to aid the development of organic semiconductors with high-quality micro/nanostructures for large-scale application and low-cost optoelectronic devices.</P>

<P>Graphic Abstract</P><P>An organic phototransistor (OPT) was fabricated using solution grown, periodic arrays of PTCDI-C<SUB>8</SUB> single crystals. The OPT exhibited high photosensitivity (7 A W<SUP>−1</SUP>), high on/off current ratio (2.5 × 10<SUP>3</SUP>) and reproducible photo-switching at low optical power.
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