Biased internal potential distributions in a bulk-heterojunction organic solar cell incorporated with a TiOx interlayer

External-biased potential distributions of a polymer bulk-heterojunction (BHJ) solar cell, incorporated with electron/hole transporting layers, were directly obseved through a cross-sectional Kelvin probe force microscopy. The bulk electric field of BHJ was found to be nearly field-free even under reverse biases, and the field-free region was probed to expand with the incorporation of TiOx electron transporting layer; as a result, inducing a decrease of quasi-Fermi level splitting region in obtaining a high fill factor in the TiOx-interlayered junction photodiodes. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4722802]