Date of this Version
Science sciencemag.org/content/early/recent / 29 January 2015 / Page 1 / 10.1126/science.aaa5760
Long, balanced electron and hole diffusion lengths greater than 100 nanometers in polycrystalline CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We report that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 μm under 1 sun illumination and exceed 3 mm under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3 mm-thick single crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, lifetime and dramatically smaller trap densities in the single crystals than polycrystalline thin-films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy-harvesting through gammavoltaic effect with an efficiency of 3.9% measured with an intense cesium-137 source.