Aggregation Regulation Of Electrochemical Deposited Films Of Polycyclic Aromatic Hydrocarbons And Their Exciton/carrier Transport Behavior

Electrochemical deposition is an efficient and controllable method for preparing organic semiconductor films.Because of irreversible redox reaction and rapid film deposition rate,the intemolecular arrangement of electrodeposited films is always disordered.At present,in order to effectively regulate the aggregation structures of electrodeposited films,researchers have developed a variety of technologies such as template method,epitaxial polymerization and compound deposition to obtain organic crystalline films.However,these methods are operationally complicated,or only obtain non-continuously distributed nanostructures on electrodes.Therefore,the regulation of aggregation in electrochemical deposition remains a substantial challenge.Because of their in-plane?-?-conjugation,polycyclic aromatic hydrocarbons(PAHs)can host strong intemolecular force,which facilitate self-assembly to form crystal structures.Therefore,we used electrochemical deposition to prepare PAH films with highly ordered and compact molecular arrangement.To avoid crystal defects caused by impurities in film,precisly electrochemical synthesis of PAH products is the first problem to be solved.For small-size PAHs,such as ortho-terphenyl,high reactive cations are formed during oxidation,causing further intermolecular coupling reaction after the intramoleucar cyclodehydrogenation of precursors.We avert the intermolecular coupling reaction by stirring electrolytes to force convection and thus gain theoretical smallest PAH product.The larger PAH precursors,due to their reduced cation activity,are tend to produce incompletely cyclodehydrogenated products,which can be effectively avoided by indirect electrolysis using auxiliary oxidant.Hexabenzene(HPB)is the most typical molecule in PAHs.We attached six phenyls on the periphery of HPB to synthesize HPB-6ph precursor for electrodeposition after rational molecular design.In the electrochemical oxidation,the HPB core form flattened HBC by electrocyclic,generating strong intermolecular?-?interaction.In addition,the crystal structure of HBC-6ph shows that the peripheral phenyls between adjacent molecules are interlaced and stacked with each other,leading to the C-H??force.The synergistic effect of these two forces promote the HBC-6ph to self-assemble to form evenly dispersed single-crystal nanorods during electrochemical deposition.On the other hand,by using monolayer graphene as electrodes,face-on configuration of all nanostructures can be achieved and thus manifested anisotropic properties.The highly ordered stacking structures in HBC-6ph films can facilitate the charge transport ability.Different spectroscopic characterizations indicate that the HBC-6ph film has excellent carrier and kinetic transport properties,including high carrier mobility(30.9±6.0 cm² V^-1 s^-1)and long exciton diffusion length(45 nm).We farbricate two-layer organic photodetection(OPD)and organic solar cell(OPV)devices using HBC-6ph films as electron donor layer.The resulting OPD devices have a detectivity of 5.81×10¹¹ Jones,while the conversion efficiency of OPV is 3.2%.