Fig. 2: Short-range overscreening effect.

a Dependence of the ICT state binding energy V_C between charged host-dopant pairs on the inverse distance between them, r⁻¹, in NPB:F₆TCNNQ (5%), computed with quantum embedding (QuantumPatch, (blue)) method and estimated via a multipole representation (red), in comparison with classical Coulomb interaction between two monopoles in polarizable medium with dielectric permittivity ϵ_r = 2.7) (gray line). For short distances, V_C of our proposed model is weaker than classical monopole–monopole interaction. b V_C(r⁻¹) estimated for 10,000 pairs indicates a distance-dependent disorder of V_C. On top: distribution of the distances from a dopant to the nearest host molecules. Auxiliary lines are sums of monopole–monopole and monopole–quadrupole interactions in three orthogonal host–dopant orientations, as shown in the insets. The orientation of the host and dopants relative to the coordinate system is also shown in Supplementary Fig. 1.