A methanol-soluble diamine-modified fullerene derivative（denoted as PCBDANI）was applied as an efficient cathode buffer layer（CBL）in planar p-i-n perovskite solar cells（pero-SCs）based on the CH;NH;PbI;Cl;absorber.The device with PCBDANI single CBL exhibited significantly improved performance with a power conversion efficiency（PCE）of 15.45%,which is approximately17%higher than that of the control device without the CBL.The dramatic improvement in PCE can be attributed to the formation of an interfacial dipole at the PCBM/Al interface originating from the amine functional group and the suppression of interfacial recombinationby the PCBDANI interlayer.To further improve the PCE of pero-SCs,PCBDANI/LiF double CBLs were introduced between PCBM and the top Al electrode.An impressive PCE of 15.71%was achieved,which is somewhat higher than that of the devices with LiF or PCBDANI single CBL.Besides the PCE,the long-term stability of the device with PCBDANI/LiF double CBLs is also superior to that of the device with LiF single CBL.
