Extended Data Figure 6: Ambient stability of ultrahigh- and ultralow-work-function films.

a, b, Self-compensated p-doped P4. a, Time-dependent optical spectra of a 12-nm-thick film in ambient conditions (295 K, 65% relative humidity (RH)). The initial doping level was x ≈ 0.8. b, To compare the stability imparted by different counter-anions, the doping level is shown as a function of exposure time for P4 (with tethered trifluoromethylsulfonylimide counter-anion; blue) and P3 (with tethered sulfonate counter-anion; red). The films were hole-doped with 1 mM NOSbF₆ in acetonitrile and self-compensated by spin-rinse with acetonitrile in a N₂ glove box, and then exposed to ambient conditions and measured after specified intervals. The doping level was evaluated from the integrated polaron band intensity (460–540 nm). Time to 50% doping level: P4, 50 h; P3, 15 min from initial doping level of about 0.8 holes per r.u. c, d, Self-compensated n-doped N1. c, Time-dependent optical spectra of a 7.5-nm-thick self-compensated film in ambient conditions. The initial doping level was x ≈ 1.0. d, To compare the stability of self-compensated and non-self-compensated films, the doping level is shown as a function of exposure time for N1 (with tethered trimethylammonium counter-ion; blue) and N0 with unbonded Na⁺ (red) or Cc⁺ (cobaltocenium; green) counter-ions. The films were electron doped with 15 mM sodium 9,10-diphenylanthracenide in diglyme and self-compensated by spin-rinse with acetonitrile. The doping level was evaluated from the integrated band intensity (540–700 nm) after calibration. Time to 50% doping level: N1, 2 h; N0 counter-balanced by Cc⁺, 20 min; N0 counter-balanced by Na⁺, 4 min from initial doping level of about 1.0 electrons per r.u. Effective ionic radius r_ion: Na⁺, 1.0 Å; Cc⁺, 3. Å; −(CH₂)₃NMe₃⁺, 3.2 Å. De-doping recovers the original π–π* spectrum.