Synthesis And Application Of N-type Organic Semiconductors Based On Multi-fused Ladder-type Units

Organic semiconductors play an important role in developments and applications of organic electronic devices.The past few years have witnessed significant progress in p-type organic semiconductors.In contrast,n-type organic semiconductors have limited molecular diversity,and their device performances?e.g.electron mobility?still lag far behind p-type organic semiconductors.Thus,it is crucial to develop some novel n-type organic semiconductors.Multi-fused ladder-type arenes have been widely used for designing p-type organic semiconductors,in terms of their good solubility,adjustable energy levels of the frontier molecular orbitals,a high degree of backbone coplanarity.In this thesis,by introducing strong electron-withdrawing functional groups,we are committed to designing and synthesizing some novel n-type organic semiconductors that based on multi-fused ladder-type arenes.With the different connecton's position or type of electron-withdrawing functional groups,multi-fused ladder-type can be applied for designing two types of n-type organic semiconductors.One is A-D-A type non-fullerene acceptor with two acceptor end-capping both sides of multi-fused ladder-type units,the other is multi-fused ladder-type arenes with the n-type characteristic that incorporating some electron-withdrawing functional groups into the backbone of multi-fused ladder-type units.In this thesis,through designing and synthesizing some novel multi-fused ladder-type units then introducing electron-withdrawing motifs,we designed and synthesized some n-type organic semiconductors.Firstly,a fused five-heterocyclic ring containing selenium atoms?IDSe?was used to design an acceptor-donor-acceptor?A-D-A?type non-fullerene acceptor?IDSe-T-IC?.The polymer solar cell?PSC?based on J51: IDSe-T-IC gives a maximum PCE of 8.6%,with a high Voc of 0.91 V,a Jsc of 15.20 m A cm^-2 and a fill factor?FF?of 62.0%.This device performance is much better than that of J51: PC71 BM based PSCs under similar device fabrication conditions?PCE = 6.0%?.Then through increasing a fused five-heterocyclic ladder-type unit IDT from five-fused number to ten-fused number,we designed and synthesized a fused ten-heterocyclic ladder-type unit IDTIDT.Another A-D-A type non-fullerene acceptor IDTIDT-IC based on this ten-heterocyclic unit was designed and synthesized.The PSCs based on acceptor IDTIDT-IC and donor PTB7-Th have a maximum PCE of 6.5%,with a high Voc of 0.94 V,a Jsc of 14.49 m A cm^-2 and a fill factor?FF?of 47.5%.Besides,this IDTIDT-IC based PSC shows a small energy loss?0.59 e V?with a high external quantum efficiency?EQE?of 63%.Finally,by replacing a cyclopenta-1,3-diene of traditional mutil-fused ladder-type unit indacenodithiophene?IDT?with a cyclohepta-4,6-diene-1,3-diimide,IDT that is a promising electron-rich donor was transferred to a new five-heterocyclic electron-deficient unit BBI.Three BBI-based donor-acceptor?D-A?polymers were designed and synthesized.All of these conjugated polymers show n-type transport characteristic with high electron mobilities,the maximum electron mobility up to 0.34 cm² V^-1s^-1.Overall,multi-fused ladder-type arenes are promising building blocks for designing n-type organic semiconductors,especially A-D-A non-fullerene acceptors and n-type D-A conjugated polymers,for use in organic solar cells or organic field-effect transistors.