Simultaneous enhancement in both large-area coatability and photovoltaic performance of inverted organic solar cells with co-solvent

We report our observation of simultaneous enhancement in large-area coatability and photovoltaic performance for blade-coated inverted P3HT:PCBM organic solar cells with DCB:hexane co-solvent. The addition of hexane improves greatly the wettability of P3HT:PCBM blend layer on Cs2CO3 treated ITO and leads to excessively higher P3HT surface concentration due to the incongruent evaporation of hexane and DCB. A post-processing light soaking was found to further improve the photovoltaic performance for blade-coated devices prepared with co-solvent by adjusting the P3HT surface concentration ratio for more favorable carrier transport, as evidenced by the disappearance of current suppression at forward bias and significant increase in V-oc after light soaking. Since large-area manufacturing is the key to full commercialization of organic solar cells, the use of co-solvent, combined with light soaking, may be crucial for the development of inverted organic solar cells. (C) 2013 Elsevier B.V. All rights reserved.