N-Type Molecular Doping in Organic Semiconductors: Formation and Dissociation Efficiencies of a Charge Transfer Complex

Abstract

Electrical doping is an important method in organic electronics to enhance device efficiency by controlling the Fermi level, increasing the conductivity, and reducing the injection barrier from the electrode. To understand the charge generation process of the dopant in doped organic semiconductors, it is important to analyze the charge transfer complex (CTC) formation and dissociation into a free charge carrier. In this paper, we correlate the charge generation efficiency with the CTC formation and dissociation efficiency of an n-dopant in organic semiconductors. The CTC formation efficiency of Rb2CO3 linearly decreases from 82.8% to 47.0% as the doping concentration increases from 2.5 to 20 mol %. The CTC formation efficiency and its linear decrease with the doping concentration are analytically correlated with the concentration-dependent size and number of dopant agglomerates by introducing the degree of reduced CTC formation. Lastly, the behavior of the dissociation efficiency is discussed on the basis of the picture of the statistical semiconductor theory and the frontier orbital hybridization model