A self-assembled monolayer (SAM) with a fused 7H-dibenzo[c,g]carbazole terminal group, a butyl linker, and a phosphonic acid group servicing as the anchor. MeO-4PADBC is the methoxy substituted 4PADCB, which is a known hole transport layer (HTL) material for highly efficient inverted perovskite and all perovskite tandem solar cells.
MeO-4PADBC is normally used in combination of NiOx, serving as a thermally robust hole-selective layer (HSL) to improve and stabilize the NiOx/perovskite interface. The MeO-4PADBC molecules form tridentate bond with the NiOx film to effectively reduce the voltage loss and maintain a strong fixation effect under thermal stress. This hole-extraction layer demonstrates an optimal dipole moment and favourable contact with the perovskite film, giving low defect density, an ideal energetic alignment, and fast hole extraction.
Verified power conversion efficiency (PCE) of 25.6% is achieved for p-i-n perovskite solar cells based on NiOx/MeO-4PADBC hole-extraction layer and a more than 90% of their initial efficiency is retained after continuously operating at 65 degrees Celsius for 1200 hours under 1 sun illumination.
Serving as hole selective contact for organic solar cells and perovskite solar cells, MeO-4PADBC is an alternative to PEDOT:PSS with superior performance and the convenience of solution deposition at low concentration, i.e. 1 mM.