Single crystal dielectrics are ideal candidates for high-performance organic field-effect transistors (OFETs) due to the ordered molecular packing and smooth surface. However, it doesn't obtain much attention due to the lack of facile preparation methods. Here, solution-grown smooth poly(e-caprolactone) (PCL) single crystals with width in tens of microns are obtained and used as the dielectric for the OFETs. The interface between the semiconductor and the PCL single crystal dielectrics are more favorable to the charge carrier transport than spin-coated PCL thin-film dielectrics, exhibiting much higher charge mobility. With 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) single crystal as semiconductor layer, the average OFET mobility reaches up to 1.70 +/- 0.97 cm(2)V(-1)s(-1) with the highest value of 4.95 cm(2)V(-1)s(-1). This result demonstrated that structural ordering of the polymer dielectrics is critical to further advance the performance of OFET devices. (C) 2018 Elsevier Ltd. All rights reserved.