P-n heterojunction and Schottky barrier formation between poly(3-methylthiophene) and n-type cadmium sulfide

摘要

Abstract: The electrical and optical properties of the junction between undoped semiconductor-like or highly doped metallic-like films of PMeT $LB@PMeT $EQ poly(3-methylthiophene)$RB and n-CdS are described. The junctions were prepared by photoelectrochemical deposition of the polymer onto the semiconductor surface from a solution of the monomer. Dark J-V measurements of the PMeT(undoped):n-CdS contact indicate rectifying behavior characteristic of a p-n junction diode, thus confirming that the undoped polymer is p-type. The photocurrent- photovoltage characteristics of the heterojunction under illumination appear stable, showing little sign of deterioration over a five-day period of observation. The presence of charge recombination centers at the p-PMeT:n-CdS interface and in the bulk is indicated. The photoresponse spectrum of the cell suggests that the observed photocurrent is due to both the polymer and n-CdS. The dark J-V characteristics of the PMeT(doped):n-CdS junction also signify a rectifying barrier. The rectification ratio of the junction is typical of a good metal- semiconductor contact. The electrical and photovoltaic properties of the doped polymer-based cell compare favorably with those of metal:n-CdS Schottky barrier devices. The parameters of the hybrid organic-inorganic heterojunction are compared with those of the Schottky barrier. !