The fabrication of polymer solar cells on large-area, flexible substrates offers the possibility for developing lower-cost commercial solar cells, although their efficiency is still quite low compared to other thin film solar cells. Here, we have investigated polymer-nanoparticle (NP) hybrid solar cells consisting of donor polymers and CdSe or ZnO nanoparticles. The P3HT-CdSe hybrid solar cells show a power conversion efficiency (PCE) of 1.46 %. The MDMO-PPV:ZnO hybrid solar cells show a PCE of 1.26 % The low PCE is due to insulating organic ligands in NP surfaces and poor network of NP nanocrystals for the extraction of electrons. © 2012 IEEE.