A New Look into 4-(2,3-Dihydro-1,3-Dimethyl-1H-Benzimidazol-2-Yl)-N,N-Dimethylbenzenamine (DMBI-H) N-Type Dopant: Not so Stable After All, but It Does Not Necessarily Matter

4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (DMBI-H) is a very successful dopant for n-type organic semiconductors. It is efficient over a large range of polymers and small molecule derivatives, commercially available, soluble in established processing solvents and generally considered to be air stable. Yet, on a closer look not all that glisters is gold. We show that DMBI-H does indeed decompose in the processing solvent, but the process does not negatively impact performances. Its main decomposition product acts as a nucleating agent for DMBI-H with the overall effect of boosting conductivity of the final doped P(NDI2OD-T2) films. Such results, confirmed by control experiments performed with a different nucleating agent, shine a light on the crucial role played by solid-state microstructure in DMBI-H doped semiconductors and hints a viable way to its optimization