In the present paper we report, effect of conjugated polymer (polyaniline) impinging in nanostructured CdS/CuInSe2 heterojunction thin film solar cell. The heterojunction architecture for the solar cell is achieved by sandwiching the conjugated conducting polymer in n and p type of wide band gap semiconducting material by multilayer chemical deposition methods onto the ITO coated glass substrate at room temperature. The obtained multilayer thin film heterojunction of ITO/CdS/Polymer/CuInSe2/Ag has been characterized for structural, compositional, optical and solar cell characteristics by illuminating it to 100 mW/cm(2) intensity light source. The X-ray diffraction pattern (XRD) confirms formation of CdS/CuInSe2 phase while on polymer impinging the crystallite size observed to be increased from 13 to 19 nm. The compositional analysis by energy dispersive X-ray spectra (EDAX) supports presence of expected elements in the heterojunction. The energy band gap calculated from absorbance spectra shows significant shift in its value from polymer and CdS/CuInSe2 band gap. I-V analysis shows increase in conversion efficiency from 0.26 in CdS/CuInSe2 to 0.55% in CdS/Polymer/CuInSe2 heterojunction upon illumination. (C) 2011 Elsevier Ltd. All rights reserved.