Fig. 3: Tuning hole mobility using short-range overscreening effect.

a Distance-dependent V_C for NPB doped with 5 mol% TCNQ, F₄TCNQ, F₆TCNNQ (color) and for dopants with artificially modified quadrupole Q_zz between −200 \(e{a}_{0}^{2}\) and 200 \(e{a}_{0}^{2}\) (gray, darker means larger Q_zz in steps of \(25\,e{a}_{0}^{2}\)). An increase in overscreening is observed for positive quadrupoles, negative quadrupoles diminish the overscreening. At a host–dopant distance of 5.3 Å (distance with the highest probability, see the top of Fig. 2b), V_C depends linearly on Q_zz (inset) and shows a variation of 0.4 eV. b Mean and its standard error of the hole mobility (points and error bars, respectively) in dependence of Q_zz shows a variation over two orders of magnitude, indicating an important dimension in the design of dopants.