PEDOT is the most popularly used conductive polymer due to its high conductivity, good physical and chemical stability, excellent optical transparency, and the capabilities of easy doping and solution processing. Based on the advantages above, PEDOT has been widely used in various devices for energy conversion and storage, and bio-sensing. The synthesis method of PEDOT is very important as it brings different properties which determine its applications. In this mini review, we begin with a brief overview of recent researches in PEDOT. Then, the synthesis methods of PEDOT are summarized in detail, including chemical polymerization, electrochemical polymerization, and transition metal-mediated coupling polymerization. Finally, research directions in acquiring high-quality PEDOT are discussed and proposed.

Plastic electrodes are desirable for the rapid development of flexible organic electronics. In this article, a plastic electrode has been prepared by employing traditional conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and plastic substrate polyethersulfone (PES). The completed electrode (Denote as HC-PEDOT:PSS) treated by 80% concentrated sulfuric acid (H₂SO₄) possesses a high electrical conductivity of over 2673 S/cm and a high transmittance of over 90% at 550 nm. The high conductivity is attributed to the regular arrangement of PEDOT molecules, which has been proved by the X-ray diffraction characterization. Temperature-dependent conductivity measurement reveals that the HC-PEDOT:PSS possesses both semiconducting and metallic properties. The binding force and effects between the PEDOT and PEI are investigated in detail. All plastic solar cells with a classical device structure of PES/HC-PEDOT:PSS/PEI/P3HT:ICBA/EG-PEDOT:PSS show a PCE of 4.05%. The ITO-free device with a structure of Glass/HC-PEDOT:PSS/Al4083/PM6:Y6/PDINO/Ag delivers an open-circuit voltage (V_OC) of 0.81 V, short-circuit current (J_SC ) of 23.5 mA/cm², fill factor (FF) of 0.67 and a moderate power conversion efficiency (PCE) of 12.8%. The above results demonstrate the HC-PEDOT:PSS electrode is a promising candidate for all-plastic solar cells and ITO-free organic solar cells.

Interface engineering is one of the key issues in fabricating efficient and stable perovskite solar cells (PSCs). Herein, we introduced self-assembled molecules of 3,4,5-trimethoxyphenylacetic acid (PAA) and 3,4,5-trimethoxyphenylpropionic acid (PPA) as a multifunctional linker to modify the buried interface between SnO2 and the Cs/FA perovskite. These modifiers can simultaneously bond to the SnO2 surface and chemically interact with perovskite to passivate the surface defects. Moreover, the PAA/PPA can facilitate the crystal growth of perovskite to form high-quality films. Accordingly, the defect density and trap-assisted charge recombination at the interface and within the perovskite are markedly reduced. Additionally, the large dipole moments of modifiers induce the modulation of energy level of SnO2, resulting in the favorable band alignment and thus the enhanced electron extraction and transport. As a result, PPA is certified to be more effective in interfacial regulation, and the Cs/FA-based PSC produces a significantly increased PCE of 22.2% with inhibited hysteresis, higher than the control (20.0%) and PAA-modified (21.5%) ones. Meanwhile, the unencapsulated devices with PAA/PPA modification presented much better ambient and thermal stability than the control device.