Doping Of Organic Conjugated Polymers And Its Applications In Organic Electronics

Organic conjugated polymers have unique electrical/optical properties that enable semiconductor/conductor applications such as photoelectric conversion and charge conduction.Besides,their outstanding advantages such as flexibility,light-weight and solution processability endow them great capability to complement silicon-based technology in modern microelectronic devices.Doping in organic semiconductors allows for effective modification of the energy level structure as well as charge transport abilities.Doped organic conjugated polymers have achieved breakthroughs in recent years,thanks to the development of various conjugated polymer structures and doping methods,as well as the optimisation of organic electronic device techniques.Nowadays,a variety of organic conductive polymers with high electrical conductivity have been used for large-scaled industrial applications and have shown great promise in organic solar cells,organic electrochemical transistors,organic thermoelectric devices and other fields.This thesis focuses on the doping of organic conjugated polymers and their applications in organic electronics.It can be divided into two themes: first,the controlled tuning of versatile properties of organic conjugated polymers through highly efficient doping;second,the structure construction,doping methods and mechanisms investigation of n-doped organic conjugated polymers.In Chapter 2,new p-type dopants were synthesized based on 2,2,6,6-tetramethylpiperidine1-oxyl(TEMPO),which could efficiently dope a variety of conjugated polymers by charge transfer.The modulation of its counterions enabled secondary doping of PEDOT:PSS as well as multi-dimensional modification of conductivity,work function and surface energy.This work expands the scope of application of doping and provides an approach for the controlled multi-property tuning of organic conjugated polymers through doping.In Chapter 3,the diradical unit benzobisthiadiazole(BBT)was introduced into the backbones of n-type conjugated polyelectrolytes for the first time and conjugated polyelectrolytes PFNBBTx-Br were synthesised using the ternary copolymerization.The effect of the diradical unit BBT on n-doping was investigated,and the results confirmed that the introduction of BBT could significantly promote the aromatic-antiaromatic resonance transition of the polymer backbone,facilitating n-type self-doping and improving the electrical conductivity of the conjugated polyelectrolyte.This work provides an effective strategy for the structural design of n-type conjugated polyelectrolytes and their efficient self-doping.In Chapter 4,the effect of diradical units on the n-doping of conjugated polymers was further investigated based on previous work.Two units,thiophenothiadiazole and benzobisthiadiazole,which have diradical resonance properties,were selected and polymerised with different copolymer units to produce a series of conjugated polymers.The doping quenching mechanism and stability were studied,and results confirmed that water could work as a quencher for anion carriers in conjugated polymers.The n-doping quenching effect of polymers was further related to photocatalytic performance,which has reference significance for the design of efficient n-doped polymers and high-performance organic photocatalysts.Moreover,it is found that the in situ doping of the conjugated polymers during the reaction can be achieved through the rational design of the polymer structure and polymerisation method,which would provide a new synthetic method and solution for the preparation of n-type conjugated polymers with high doping efficiency.In Chapter 5,the possibility of achieving in situ n-type doping of conjugated polymers during the reaction was further explored based on the work in the previous chapter.The transition metal-free aldol condensation reaction was applied and the precursor with quaternary ammonium functional groups in the side chains was synthesised,which was polymerised with the electron-withdrawing unit benzofurandione to achieve in situ n-doping of the conjugated polyelectrolyte.The conjugated polyelectrolyte exhibited strong polaron absorption in the near infrared region,as well as high electrical conductivity and good air stability.This work provides a new idea and strategy for the synthesis of self-doped n-type conjugated polyelectrolytes.