Highly Doped Conjugated Polyelectrolytes with Large Work Function for Efficient Hole Injection/Collection in Organic Photoelectric Devices

The existing deficiencies in traditional hole‐transporting layer (HTL) materials poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and molybdenum oxide restrict the further advance in the photoelectric conversion efficiency of organic photoelectric devices. Although conjugated polyelectrolytes (CPEs) display great advantage in serving as HTLs, the low work function (WF) and poor conductivity lead to the inferior performances of CPE‐modified devices. Herein, the important influence of electrostatic potential on p‐doping property of CPEs is revealed, and hence a series of CPEs with obvious p‐type self‐doping property based on simple chemical structures of benzene and thiophene derivatives are designed and synthesized. With a higher electron density of conjugated backbone, the CPE PB3T shows an improved doping effect. Moreover, a simultaneous enhancement of WF and conductivity can be achieved by doping the CPE with polyoxometalate (POM). The resulting CPE composite PB3T:POM exhibits good hole injection/collection ability and is compatible with large‐area production technique. The organic solar cells with active areas of 0.04 and 1.00 cm 2 exhibit power conversion efficiency values of 18.1% and 15.6%, respectively. PB3T:POM is also used as HTL to fabricate organic light‐emitting diode (OLED) device, and the OLED exhibits a superior luminous efficiency to the PEDOT:PSS device but with a significantly reduced turn‐on voltage from 4.2 to 3.4 V.