Hole Extraction Enhancement for Efficient Polymer Solar Cells with Boronic Acid Functionalized Carbon Nanotubes doped Hole Transport Layers

Boronic acid functionalized multiwalled carbon nanotubes (bf-MWCNTs) were synthesized via a facile low temperature process and introduced in PEDOT:PSS as the composite hole transport layer (HTL), which improved the power conversion efficiency (PCE) of polymer solar cells (PSCs). The devices utilized PCDTBT:PC71BM active layers had achieved an optimal PCE of 6.953%, leading to 28% enhancement comparing to the device based on pristine PEDOT:PSS HTL. The PEDOT:PSS:bf-MWCNTs composite HTLs exhibited remarkable enhancement on hole mobility and electrical conductivity, which were beneficial to the hole extraction and transport on interface. Meanwhile, the work function (WF) of HTLs had an increase after bf-MWCNTs doping, which was matched with the highest occupied molecular orbital (HOMO) of the donor material, further improving the hole transport. Therefore, the incorporation of bf-MWCNTs efficiently improved the hole extraction and transport from active layer to the electrode.