We report about the fabrication and electrical characterization of heterojunction diodes between poly (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) doped with dimethyl sulfoxide (DMSO) and p-Si. Electrical characterization of the heterojunction diodes was performed using current-voltage (I-V) measurements. The heterojunction diodes showed good rectifying behavior. Interestingly, for 5 vol.% doping concentration of DMSO, the heterojunction diode showed the best diode characteristics with an ideality factor of 1.9. The doping of DMSO into PEDOT: PSS solution resulted in an increase in the conductivity of films by two orders of magnitude and the films showed high optical transmission (>85%) in the visible region. (C) 2016 Elsevier B.V. All rights reserved.