This article briefly introduces my 30 years research carrier on conjugated polymers in Institute of Chemistry

Chinese Academy of Sciences (ICCAS). The achievements mentioned here mainly focus on the fields of conjugated polymers

including the electrochemistry of conducting polypyrrole (PPy)

polymer light-emitting electrochemical cells (LECs) and conjugated polymer donor materials for polymer solar cells (PSCs). In the field of electrochemistry of conducting PPy

I and my group systematically studied the electrochemical preparation and electrochemical properties of conducting PPy. We elucidated the effects of various electropolymerization conditions on conductivity and mechanical properties of the as-prepared PPy films. We found that donor number of the electrolyte solvents greatly influences the conductivity of the as-prepared PPy films : the smaller the donor number of the electrolyte solvent

the greater the electric conductivity of the as-prepared PPy films. Very smooth conducting PPy films with high mechanical strength were prepared by using non-ionic surfactant additive in the aquesous electrolyte solution. For the reaction mechanism of pyrrole electropolymerization

I proposed and confirmed the solution-participated cation-radical electropolymerization mechanism

and deduced a kinetic equation for the pyrrole electropolymerization reaction. We also found that there are two doping structures (main chain oxidized with counter-anions doping structure and the proton-acid doping structure) in the conducting PPy films prepared from NaNO

3

aqueous solution. We studied and elucidated mechanisms of the reduction and re-oxidation of conducting PPy films in aqueous solutions

and the mechanisms of the first reduction and re-oxidation of conducting PPy films in organic electrolyte solutions. In the studies of LECs

I confirmed the electrochemical doping mechanism and the formation of

p-i-n

structure of the LECs after applying voltage higher than E

g

/e of the luminescent conjugated polymers by ac impedance measurements. We synthesized a series of luminescent and ionic conductive conjugated polymers with main chian containing ionic-conducting units

and the phase separation problem in the LECs was avoided by using the bi-functional polymers as the luminescent polymers in the LECs. We fabricated quasi-frozen junction LECs by using ionic liquid as electrolyte salt in the active layers of LECs which improved the electroluminescent properties of the LECs significantly. In the studies of conjugated polymer donor materials for PSCs

we proposed a molecular design strategy of two-dimension (2D)-conjugated polymers with conjugated side chains to broaden the absorption and enhance the hole mobility of the conjugated polymers for improving its photovoltaic performance. We synthesized a series of 2D-conjugated polythiophenes with conjugated side chains which show broader absorption

higher hole mobility and improved photovoltaic performance. Then the 2D-conjugation strategy was further extended to the narrow bandgap 2D-conjugated PBDTTTs by attaching thiophene conjugated side chains on benzodithiophene (BDT) units. We introduced alkylthio substituents on the thiophene conjugated side chains of the 2D-conjugated PBDTTTs and further improved their photovoltaic properties. Finally

I introduced our recent research progress on non-fullerene PSCs based on our 2D-conjugated polymers as donor and narrow bandgap n-type organic semiconductor as acceptor.