| Organic field-effect transistors?OFETs?have received extensive attention in recent years,and have been rapidly developed in the design and synthesis of high-performance materials,the device-fabrication processes,and the charge transport mechanisms.The mobilities of some OFETs can reach or exceed to the values of amorphous silicon,and can be endowed with the multi-functional properties,which has great prospects in many application areas.To clarify the relationship between multi-scale structures and electrical properties of conjugated polymers,and to simplify the OFETs-fabrication processes and optimize device performance,we have proposed an idea of preparing conjugated polymer ultrathin films in conjugated/insulating polymer blend systems.The relationship between nanoscale structures and electrical properties of conjugated polymers ultrathin films has been researched,and the charge transport and its influencing factors in ultrathin films have also been explored.A bar-coating method has been developed to fabricate large-area OFETs,and the applications of conjugated polymer ultrathin films have been broadened in low-voltage flexible OFETs and optically stable organic semiconductors.The results are obtained as follows.The conjugated/insulating polymer blend films are prepared by a bar-coating method.The morphologies of blend films can be systematically controlled by varying the concentration of P3HT and PMMA solutions,and the mechanism of phase separation have also been researched.The wafer-scale one-step OFETs,with a continuous P3HT ultrathin film,exhibite high electrical reproducibility and uniformity.The one-step OFETs have been extended to substrate-free arrays with a total thickness of less than one micron,which showed ultra-light and ultra-soft characteristics,can can be attached everywhere on varying substrates.In addition,due to the well-ordered molecular arrangement,the moderate charge transport pathway is formed,which resulted in stable OFETs under various organic solvent vapors and lights of different wavelengths.The results demonstrate that the one-step OFETs have promising potential in the field of large-area organic wearable electronics.A phase-separation method has been developed to control the semiconductor thickness and molecular arrangement via semiconducting/insulating polymer blend system and a transfer-etch process.The thickness of poly?3-hexylthiophene??P3HT?film have been regulated from 1.9 ± 0.8 nm up to 10.5 ± 1.4 nm with favorable self-assembly degree and the mobility ranging from 0.03 to 0.21 cm2 V-1 s-1,respectively.Benefited from well molecular order,the films have thickness-related activation energy and 2D charge transport profile in semiconductor layers.Moreover,this blending process can be used as general strategy of thickness control in flexible low-voltage devices and donor-acceptor conjugated polymers based on isoindigo and bithiophene.The multilayers of P3HT ultrathin films have been prepared by multiple transfer-etch processes of conjugated/insulating polymer blend films.The overall molecular order of the ultrathin film multilayers are improved after film lamination.The ultrathin film multilayers have excellent electrical properties and reaches a maximum value of 0.226 cm2 V-1 s-1 at 3L,which is close to the highest value of the undoped P3HT OFET.Regardless of the number of layers,the charge distribution is 2D dimension in the semiconductor layers,which is significantly different from the common bottom gate OFET structures.This excellent charge transport properties is attributed to the tightly ordered molecular arrangement and few traps which obtained by phase separation and lamination.In addition,the P3HT ultrathin film multilayers are insensitive to different wavelengths of visible light which are expected to be used in OFET active matrix driven displays. |
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