Abstract
We have successfully integrated two effective strategies to improve the power conversion efficiency (PCE) of bulk heterojunction inverted small molecule solar cells (i-SMSCs) by doping a ZnO cathode with a fullerene derivative (ZnO-C60) followed by fullerene derivative self-assembled monolayer (SAM) modification on its surface in contact with the active layer. Such ZnO-C60 gives a fullerene-derivative-rich interface in contact with the active layer and enhanced surface conductivity relative to pristine ZnO (from 0.015 to 1.09 S cm-1) and bulk electron mobility (from 1.23 ± 0.39 × 10-4 to 6.43 ± 0.35 × 10-3 cm2 V-1 s-1). Using this ZnO-C60 as the cathode, the device with the active layer p-DTS(FBTTh2)2:PC71BM gives a higher PCE of 8.3% than that using ZnO without doping, 6.08%. Further incorporation of fullerene derivatives (NPC60-OH and NPC70-OH) as a SAM on ZnO-C60 effectively passivates the electron traps on the ZnO-C60 surface, resulting in increased electron mobility. The device using the ZnO-C60 nanofilm with phenol substituted C70 (NPC70-OH) as the SAM gives a further promoted PCE of up to 9.14%, which is the best value among the reported values in i-SMSCs.
Original language | British English |
---|---|
Pages (from-to) | 22599-22604 |
Number of pages | 6 |
Journal | Journal of Materials Chemistry A |
Volume | 3 |
Issue number | 45 |
DOIs | |
State | Published - 2015 |