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Despite decades of research, the fundamental question of structure and morphology of the poly(3,‐4‐ethylenedioxythiophene):poly(styrene sulfonate) complex (PEDT: PSS) electrically conducting polymer remains open. Here, through a systematic study of the polymerization of 3,4‐ethylenedioxythiophene (EDT) on two series of sulfonated polystyrenes, i.e., PS‐co‐SSH and PS‐co‐SSNa, with per cent sulfonation 24 ≲ x ≲ 100, this study shows that the substrate polyelectrolyte not only affords charge compensation and processability, but also templates the morphology of the growing PEDT chain—whether extended, coiled or collapsed. This determines the electrical, electronic and optical properties of the resultant PEDT: PSS interpolyelectrolyte complexes, including their work function. This study calls this the Polyelectrolyte Template model. The PEDT: PSS complex retains memory of its polymerization morphology even after subsequent ion‐exchange, for example, to the same acid form. Electrical conductivity decreases sharply with decreasing x, and depends on whether the polymerization is templated with the H+ or Na+ form of the polyelectrolyte. The work function is less sensitive to x, but exhibits a transition from low to high work function (5.2–5.3 eV) when x exceeds a threshold, which indicates formation of a polar surface driven by molecular‐scale segregation of the PSS counteranion. This surface segregation also affects the ability of these complexes to inject holes into very large‐ionization‐energy semiconductors. [ABSTRACT FROM AUTHOR]

Electrodes with low work functions are required to efficiently inject electrons into semiconductor devices. However, when the work function drops below about 4 electronvolts, the electrode suffers oxidation in air, which prevents its fabrication in ambient conditions. Here we show that multivalent anions such as oxalate, carbonate and sulfite can act as powerful latent electron donors when dispersed as small ion clusters in a matrix, while retaining their ability to be processed in solution in ambient conditions. The anions in these clusters can even n-dope the semiconductor core of [pi]-conjugated polyelectrolytes that have low electron affinities, through a ground-state doping mechanism that is further amplified by a hole-sensitized or photosensitized mechanism in the device. A theoretical analysis of donor levels of these anions reveals that they are favourably upshifted from ionic lattices by a decrease in the Coulomb stabilization of small ion clusters, and by irreversibility effects. We attain an ultralow effective work function of 2.4 electronvolts with the polyfluorene core. We realize high-performance, solution-processed, white-light-emitting diodes and organic solar cells using polymer electron injection layers with these universal anion donors, demonstrating a general approach to chemically designed and ambient-processed Ohmic electron contacts for semiconductor devices. Multivalent anions are found to be capable of electron-doping polymer semiconductors to realize conductive films with very low work functions, which enable efficient electron injection into materials with low electron affinity., Author(s): Cindy G. Tang [sup.1] , Mazlan Nur Syafiqah [sup.2] , Qi-Mian Koh [sup.2] , Chao Zhao [sup.1] , Jamal Zaini [sup.2] , Qiu-Jing Seah [sup.2] , Michael J. Cass [...]