Efficiency exceeding 10% for inverted polymer solar cells with a ZnO/ionic liquid combined cathode interfacial layer

Abstract

The interlayer inserted between the active layer and ITO has been demonstrated to be crucial for the performance of inverted polymer solar cells (i-PSCs). In this work, we find that ionic liquids (ILs) can significantly enhance the efficiency of i-PSCs. With the ZnO/IL interfacial layer, PTB7-Th : PC₇₁BM i-PSCs can exhibit a champion power conversion efficiency (PCE) of 10.15%, which is among the highest PCEs reported thus far for single-junction bulk heterojunction solar cells through the solution process. The IL layer and ZnO/IL combination layer with low work function, good optical transmittance, improved electron extraction and reduced resistance at the cathode interface have been demonstrated to be excellent and general interfacial layers for i-PSCs.