Extended Data Figure 3: Doping-profile migration in the presence of mobile counter-ions.

a, b, Schematic (a) and experimental data (b) for transfer of holes and counter-ions from a hole-doped organic semiconductor layer with mobile counter-anions (OSC-1) to an adjacent organic semiconductor layer (OSC-2) during solution processing. OSC-1 is P0 (I_P = 5.9 eV), hole-doped to x ≈ 0.8, with SbF₆⁻ as counter-ion. OSC-2 is OC₁C₁₀-PPV (I_P = 5.0 eV), deposited by spin-casting on p-doped P0. c, d, Schematic (c) and experimental data (d) for transfer of holes and counter-ions from an incompletely self-compensated hole-doped organic semiconductor (OSC-1) to an adjacent organic semiconductor layer (OSC-2) during solution processing. OSC-1 is incompletely self-compensated hole-doped P1 (x ≈ 0.8) containing 50% residual Na⁺ and SbF₆⁻. OSC-2 as in a and b. Nearly complete transfer of holes and counter-anions from the doped underlayer to the OC₁C₁₀-PPV overlayer occurred during spin-casting, as evidenced by emergence of the polaron band of OC₁C₁₀-PPV (600–800 nm) and bleaching of the polaron band of P0 and P1 (>900 nm). This doping transfer is driven by thermodynamics from a high-I_P layer to a low-I_P layer. E_f, Fermi energy; VL, vacuum level.