title: Boron Doping of Multiwalled Carbon Nanotubes Significantly Enhances Hole Extraction in Carbon-Based Perovskite Solar Cells.
abstract: Compared to the conventional perovskite solar cells (PSCs) containing hole-transport materials (HTM), carbon materials based HTM-free PSCs (C-PSCs) have often suffered from inferior power conversion efficiencies (PCEs) arising at least partially from the inefficient hole extraction at the perovskite-carbon interface. Here, we show that boron (B) doping of multiwalled carbon nanotubes (B-MWNTs) electrodes are superior in enabling enhanced hole extraction and transport by increasing work function, carrier concentration, and conductivity of MWNTs. The C-PSCs prepared using the B-MWNTs as the counter electrodes to extract and transport hole carriers have achieved remarkably higher performances than that with the undoped MWNTs, with the resulting PCE being considerably improved from 10.70% (average of 9.58%) to 14.60% (average of 13.70%). Significantly, these cells show negligible hysteretic behavior. Moreover, by coating a thin layer of insulating aluminum oxide (Al2O3) on the mesoporous TiO2film as a physical barrier to substantially reduce the charge losses, the PCE has been further pushed to 15.23% (average 14.20%). Finally, the impressive durability and stability of the prepared C-PSCs were also testified under various conditions, including long-term air exposure, heat treatment, and high humidity.
authors.forename: Xiaoli
authors.identifier: 0000-0001-5190-4331
authors.initials: X
authors.lastname: Zheng
authors.affiliation: School of Materials Science and Engineering, Beihang University , Beijing 100191, China.
authors.forename: Haining
authors.identifier: 0000-0002-7543-3674
authors.initials: H
authors.lastname: Chen
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.forename: Yinglong
authors.initials: Y
authors.lastname: Yang
authors.forename: Zhanhua
authors.initials: Z
authors.lastname: Wei
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.forename: Yongcai
authors.initials: Y
authors.lastname: Qiu
authors.forename: Dan
authors.initials: D
authors.lastname: Zhou
authors.forename: Kam Sing
authors.initials: KS
authors.lastname: Wong
authors.forename: Shihe
authors.initials: S
authors.lastname: Yang
keywords: Carbon-based perovskite solar cell; Fermi level; boron-doping carbon nanotubes; carrier concentration; hole extraction