title: Long-range balanced electron- and hole-transport lengths in organic-inorganic CH3NH3PbI3.
abstract: Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.
authors.affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University (NTU), 21 Nanyang Link, 637371 Singapore.
authors.forename: Guichuan
authors.initials: G
authors.lastname: Xing
authors.forename: Nripan
authors.initials: N
authors.lastname: Mathews
authors.forename: Shuangyong
authors.initials: S
authors.lastname: Sun
authors.forename: Swee Sien
authors.initials: SS
authors.lastname: Lim
authors.forename: Yeng Ming
authors.initials: YM
authors.lastname: Lam
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.forename: Subodh
authors.initials: S
authors.lastname: Mhaisalkar
authors.forename: Tze Chien
authors.initials: TC
authors.lastname: Sum