Highly Sensitive Polymer Phototransitor Enhanced By Synergistic Effect Of Chemical Modification And Physical Blending

Compared to photodiodes,organic phototransisitors?OPTs?can exhibit much higher sensitivities and lower noise,and have potential applications in both flexible displays and wearable electronics.Currently,some groups use trapping effect to achieve a novel and highly sensitive OPTs.However,effective control of the trapping effect is difficult.Three-component random copolymers?BTPIDBIBDFs?having different ratios of isoindigo?IID?and benzodifurandione?BIBDF?as acceptor units,and dithiophene?BT?as donor unit,were used as the active layer of OPTs in paper.Chemical doping and physical blending were used to effectively control depth of energy trap,which open up a new idea to achieve highly sensitive polymer OPTs.And the illumination sensing of flexible low-voltage OPTs was investigated.The main work of this paper is as follows:?1?The blending of semiconductor BTPIDBIBDF-5 with insulating polymers poly-?1,4-butylene adipate??PBA?was found useful in obtaining semiconductor nanowire networks?NWs?.Highly sensitive OPTs were fabricated using semiconductor NWs as the photoactive channel.The resulting BTPIDBIBDF-5 nanowire networks OPTs?NW-OPTs?exhibited a ultrahigh photo-/dark-current ratio?P?of 4.8×10⁶ and a responsivity?R?of 5.3 AW^-1.The NW-OPTs are more than six orders of magnitude higher than the structurally identical planner OPTs in terms of P,and one order of magnitude higher in terms of R.The exceptionally enhanced photoresponses of NW-OPTs were mainly attributed to the better trapping effect at the semiconductor/insulator interface.However,the causes of the trap still need to be further explored.?2?In order to explore the essential causes of the trap,the effects of different ratios of IID and BIBDF in polymer BTPIDBIBDFs on performance of devices were investigated.And improved illumination response of OPTs was obtained.In order to further improve photoresponse of devices,the polymer semiconductor and PBA were blended to act as active layer of device.The blending of semiconductor polymer BTPIDBIBDFs with different contents of PBA was used to investigate illumination response.With increase of PBA in active layer,the photoresponse of polymer BTPIDBIBDFs OPTs increase firstly,and then decrease.When the blending polymer BTPIDBIBDF-5 with 1%PBA was as the active layer,the best results show that P,R and Ratio of the best sensing devices were 3.2×10⁶,77 AW^-1 and 2500,respectively.The higher photoresponses and larger threshold voltage shifts of OPTs were mainly attributed to the chemical doping and physics blending synergistic energy trapping effect.?3?PET is as flexible substrate,and the blending 1%PBA with the polymer BTPIDBIBDF-5 is as active layer.Bottom-gate top-contact flexible low-voltage OPTs were fabricated(V_GS<10 V,V_DS<10 V).And the illumination response parameter P and R can arrive to 5.7×10⁴ and 180 mAW^-1,respectively.