Highly efficient inkjet-printed organic photovoltaic cells

In this article, we report the development of inkjet printing technique for the fabrication of bulk heterojunction organic photovoltaic cells (OPVs). We have demonstrated highly efficient OPV with a mixture of poly(3-hexylthiophene)s (P3HT) and 1-[3-(methoxycarbonyl)propyl]-1- phenyl[6.6]C61 (PCBM) as an inkjet-printed photoactive layer. Especially, 3.8% of power conversion efficiency (PCE) and 0.68 V of open circuit voltage (V_oc) can be obtained by using the chlorobenzene as a solvent. This value is the highest performance in P3HT:PCBM based OPV system by now. We reveal that substantial improvements can be realized by nano-structured heterojunction after inkjet printing and this technique is one of the promising fabrication methods for organic photovoltaic cells. Also, we have designed and fabricated five-series connected large area (18cm²) inkjet-printed OPVs using the patterned indium tin oxide (ITO) with Au bus-electrode to minimize the efficiency drop due to the surface resistance of ITO. Consequently, 1.25% of power conversion efficiency can be obtained with a short circuit current of 1.24 mA/cm ², a fill factor of 0.32, and an open circuit voltage of 3.2 V.