Boosting the Performance of Organic Phototransistors Utilizing Oriented Thin‐Films of Liquid Crystalline Conjugated Polymer PBTTT C‐14

To improve the organic field‐effect transistor (OFET) performance, the advantages of the unidirectional floating film transfer method (UFTM) are utilized to fabricate uniaxially aligned thin film of a liquid crystalline semiconducting polymer (SCP) upon a SiO ₂ surface modified with a self‐assembled monolayer (SAM) of alkyl‐silane. We deposited the SAM of octadecyl‐triethoxy silane (OTES) by spin coating onto the SiO ₂ gate dielectric surface to make the surface hydrophobic and promote the molecular self‐assembly of aligned SCP. The electrical anisotropy of the UFTM fabricated thin films of poly [2,5‐bis (3‐tetradecylthiophen‐2‐yl) thieno [3,2‐b] thiophene] (PBTTT) C‐14 were studied by constructing parallel and perpendicular OFETs. Parallel OFET exhibits a mobility of 0.13 cm ² V ⁻¹ sec ⁻¹ , a dark on‐off ratio of 2.6 × 10 ⁵ , and 0V V _th . Further, OFETs are utilized as organic phototransistors (OPTs) under monochromatic green light (525 nm) illumination at an intensity of 3 mWcm ⁻² . The photosensitivity and responsivity of parallel OPT are 6.3 × 10 ⁴ and 81 AW ⁻¹ , respectively, which are much more pronounced compared to that of the corresponding perpendicular OPT with the photosensitivity and responsivity of 2 × 10 ² and 6.2 AW ⁻¹ , respectively. This work contributes to the advancement of organic photodetector technology, offering valuable guidance for future device development and applications.