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 Voc 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.