Xing, GuichuanMathews, NripanSun, ShuangyongLim, Swee SienLam, Yeng MingGraetzel, MichaelMhaisalkar, SubodhSum, Tze Chien2013-12-092013-12-092013-12-09201310.1126/science.1243167https://infoscience.epfl.ch/handle/20.500.14299/97714WOS:000325755100040Low-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.text::journal::journal article::research article