Performance Enhancement of Organic Solar Cells with the LiF/Al Cathode Structure by the Pyromellitic Dianhydride Layer

We reported enhanced characteristics of the organic solar cells (OSCs) using pyromellitic dianhydride (PMDA) material as cathode interfacial layer. This PMDA cathode interfacial layer was used in a bilayered structure consisting of lithium fluoride (LiF) and pyromellitic dianhydride (PMDA) at the interface of poly(3-hexylthiophene-2,5-diyl)(P3HT)+[6,6]-phenyl C-61 butyric acid methyl ester (PCBM) and Al. Better performance enhancement compared to OSCs without a cathode interfacial layer or with a single LiF interfacial layer was achieved by using a bilayered interfacial structure. The OSC with a cathode interfacial structure with LiF and PMDA combination showed 2.08 % power conversion efficiency (PCE) value, while the OSC with a single LiF cathode interfacial layer showed 1.72 % PCE value and the OSC without any cathode interfacial layer showed 1.35 % PCE value, respectively. And Cole-Cole plots of OSCs showed that bilayered interfacial structure reduced impedance probably by improving the electron transport between Al and PCBM+P3HT.