Compensating Poly(3-hexylthiophene) Reveals Its Doping Density and Its Strong Exciton Quenching by Free Carriers



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Adding increasing quantities of an n-type compensating dopant, cobaltocene, to poly(3-hexylthiophene) reveals an almost perfect mirror symmetry between the conductivity and the luminescence intensity. The sharp minimum/maximum shows that the uncompensated p-type doping density is 1.2 × 1018 cm−3 and that excitons are strongly quenched by free charge carriers, not by bound charges.