Chemical doping of a semicrystalline polymeric semiconductor realizing high stability and work function

Abstract

Recently, doped organic semiconductors with high work functions have been studied for opto-electronic device applications. However, a higher work function commonly results in poorer stability due to redox reactions with water in air, limiting device processing and applications. In this study, combinations of bulky anions and a semicrystalline polythiophene derivative were explored for chemical doping under ambient conditions. The use of tetrakis(pentafluorophenyl)borate (TFPB) anions resulted in a high work function over 5.5 eV with remarkably improved stability, with 90% of the conductivity retained after storage in air for 20 days. The stability at elevated temperatures of 100 °C and 125 °C was also dramatically improved compared with the use of other dopant ions. X-ray diffraction measurements suggest that intercalation of the TFPB anion occurs in the lamellar structure of the polymer, while in-plane π-stacking structures are present. Dedoping reactions including self-degradation at high temperatures seemed to be suppressed for this inert dopant anion, which contributed to the observed exceptional stability. Our findings provide promising insights into the design of combinations of polymers and dopants to achieve highly stable doped organic semiconductors.