Flexible, Semitransparent Inverted Organic Solar Cells Using WO_3/Ag/WO_3 as Transparent Anode Electrode

摘要

Flexible and semitransparent organic solar cells require transparent electrodes on both the bottom and the top of the cells. In the present work, we have fabricated the inverted semitransparent organic solar cells composed of PEDOT:PSS/PEIE (polyethylenimineethoxylated)/P3HT:PCBM/WO_3/Ag/WO_3(WAW). In these cells, the inner WO_3 thin layer is placed between the active layer and the Ag layer to improve hole collection, while the outer WO_3 thin layer is used to enhance optical transmittance. When the thicknesses of both the Ag and the WO_3 are properly optimized, the prepared cell achieves a maximum power conversion efficiency (PCE) of 2.32%. The WAW electrode records a high transmittance of 84.3% and a low sheet resistance of approximately 7.5 ohm/sq. It should be noted that light illumination to the bottom and top electrode reveals similar PCE values of 2.32% and 2.26%, respectively. This result is mainly due to the low sheet resistance of the WAW electrode. Especially, we have investigated the physical effects of low sheet resistance on the performance of organic solar cells through the measurements of impedance spectroscopy.