Performance enhancement of CdSe nanorod-polymer based hybrid solar cells utilizing a novel combination of post-synthetic nanoparticle surface treatments

We report on improved power conversion efficiencies (PCEs) approaching 3.5% for bulk-heterojunction (BHJ) hybrid solar cells based on CdSe nanorods and the low band gap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT). Different post-synthetic surface treatments of CdSe nanorods are applied and the performances of the resulting hybrid solar cells are compared. The improved PCE values are attributed to the advanced post-synthetic surface treatment of the CdSe nanorods, leading to an effective reduction of synthesis ligands from the nanorod surfaces prior to ligand exchange with pyridine. The sequential decrease of the ligands is confirmed by a combination of thermogravimetric analysis-mass spectrometry (TGA-MS).