Crown-ether functionalized fullerene as a solution-processable cathode buffer layer for high performance perovskite and polymer solar cells

An alcohol-soluble fullerene derivative functionalized with a crown-ether end group in its side chain (denoted as PCBC) was synthesized and applied as a cathode buffer layer in planar p-i-n perovskite solar cells and bulk-heterojunction polymer solar cells. It is found that the introduction of the PCBC cathode buffer layer can greatly improve the photovoltaic performance of the planar p-i-n perovskite solar cells based on CH3NH3PbI3-xClx with power conversion efficiency (PCE) reaching 15.08%. In addition, the bulk-heterojunction polymer solar cells based on PBDTTT-C-T:PC70BM with the PCBC cathode buffer layer also showed a higher PCE of 7.67%, which is improved in comparison with the traditional device with the Ca/Al cathode. This work indicates that PCBC is a promising solution-processable cathode buffer layer material for application in both planar p-i-n perovskite solar cells and bulk-heterojunction polymer solar cells.