title: Improved hole interfacial layer for planar perovskite solar cells with efficiency exceeding 15%.
abstract: Planar structure has been proven to be efficient and convenient in fabricating low-temperature and solution-processing perovkite solar cells (PSCs). Interface control and crystal film growth of organometal halide films are regarded as the most important factors to obtain high-performance PSCs. Herein, we report a solution-processed
  PSS-GeO2 composite films by simply incorporating the GeO2 aqueous solution into the
  PSS aqueous dispersion as a hole transport layer in planar PSCs. Besides the merits of high conductivity, ambient stability and interface modification of
  PSS-GeO2 composite films, the formed island-like GeO2 particles are assumed to act as growing sites of crystal nucleus of perovskite films during annealing. By the seed-mediation of GeO2 particles, a superior CH3NH3PbI(3-x)Cl(x) crystalline film with large-scale domains and good film uniformity was obtained. The resulting PSC device with
  PSS-GeO2 composite film as HTL shows a best performance with 15.15% PCE and a fill factor (FF) of 74%. There is a remarkable improvement (∼37%) in PCE, from 9.87% to 13.54% (in average for over 120 devices), compared with the reference pristine
  PSS based device.
authors.forename: Zhao-Kui
authors.initials: ZK
authors.lastname: Wang
authors.affiliation: ‡College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Li
authors.forename: Da-Xing
authors.initials: DX
authors.lastname: Yuan
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Shi
authors.affiliation: ‡College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, China.
authors.forename: Heng
authors.initials: H
authors.lastname: Ma
authors.forename: Liang-Sheng
authors.initials: LS
authors.lastname: Liao
keywords: GeO2 nanoparticles; hole interfacial layer; perovskite solar cells; solution-processing