title: Sulfamic Acid-Catalyzed Lead Perovskite Formation for Solar Cell Fabrication on Glass or Plastic Substrates.
abstract: Lead perovskite materials such as methylammonium triiodoplumbate(II) (CH3NH3PbI3, PV) are promising materials for printable solar cell (SC) applications. The preparation of PV involves a series of energetically costly cleavages of the μ-iodo bridges via conversion of a mixture of PbI2 (PI) and methylammonium iodide (CH3NH3I, MAI) in N,N-dimethylformamide (DMF) into a precursor solution containing a polymeric strip of a plumbate(II) dimer [(MA(+))2(PbI3(-))2·(DMF)2]m, which then produces a perovskite film with loss of DMF upon spin-coating and heating of the substrate. We report here that the PI-to-PV conversion and the PV crystal growth to micrometer size can be accelerated by a small amount of zwitterionic sulfamic acid (NH3SO3, SA) and that sulfamic acid facilitates electron transfer to a neighboring electron-accepting layer in an SC device. As a result, an SC device on indium tin oxide (ITO)/glass made of a 320 nm thick PV film using 0.7 wt % SA showed a higher short-circuit current, open-circuit voltage, and fill factor and hence a 22.5% higher power conversion efficiency of 16.02% compared with the device made without SA. The power conversion efficiency value was reproducible (±0.3% for 25 devices), and the device showed very small hysteresis. The device without any encapsulation showed a respectable longevity on a shelf under nitrogen under ambient light. A flexible device similarly fabricated on ITO/poly(ethylene naphthalate) showed an efficiency of 12.4%.
authors.affiliation: Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Sato
authors.affiliation: Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Shoyama
authors.affiliation: Department of Chemistry, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Nakamura