Pyronin B as a donor for n-type doping of organic thin films

We present an approach to stable n-type doping of organic matrices using organic dopands. To circumvent stability limitations inherent in strong organic donors, we produce the donor from a stable precursor compound in situ. As an example, pyronin B chloride is studied as a dopant in a 1,4,5,8-naphthalene tetracarboxylic dianhydride matrix. Conductivities up to ${\text{2×10}}^{\text{−4}}\hspace{0.17em}\mathrm{S/cm}$ are obtained, which is two orders of magnitude higher than obtained previously using bis(ethylenedithio)-tetrathiafulvalene as a dopant [A. Nollau, M. Pfeiffer, T. Fritz, and K. Leo, J. Appl. Phys. 87, 4340 (2000)]. Field-effect measurements are used to prove n-type conduction. Other matrices which can be doped are $\mathrm{N},{\mathrm{N}}^{\prime }-\mathrm{dimethyl-perylene}\text{-3,4,9,10-}\mathrm{tetracarboxylic}$ diimide and fullerene ${\mathrm{C}}_{60},$ frequently used in organic solar cells. Visible light and Fourier-transform infrared spectroscopy confirm the donor properties of pyronin B.