Cubic iron pyrite (fool's gold) nanocrystals with an average diameter of similar to 60 nm were grown in an oleylamine ligand which acts as a solvent and surfactant without the utilization of alkyl phosphine and phosphonic acids at 230 degrees C in a Schlenk flask. For the first time photoluminescence properties of such cubic nanocrystals were analyzed at 77 K, showing band gaps of 1.71 eV. However, UV-Vis spectra shows a band gap of 1.41 eV for the same nanocrystals, close to the direct band gap (1.38 eV) of reported pyrite materials. The discrepancy of 03 eV in absorption (UV-Vis) and emission spectra (PL) are attributed to the phonon coupling (stokes shift). The prepared cubic nanocrystals were well suited for an inexpensive thin film solar cells and further processed and spin casted with a synthesized CdSe quantum dots in chloroform solvent as a bulk-heterojunction (BHJ) solar cell in order to get photovoltaic responses in real devices. We successfully report here an efficiency of 0.5% with the J(SC) of 3.7 mA/cm(-2) and V-OC of 0.16 mV with a cell structure of ITO/PEDOT:PSS/FeS2:CdSe/Au. The morphology and optoelectronic properties are elucidated by SEM, TEM, TEM-EDS, XRD, micro-Raman spectra, IV curve and micro-PL techniques. (C) 2014 Elsevier B.V. All rights reserved.