Impact of microstructure on local carrier lifetime in perovskite solar cells by Dane W. deQuilettes, Sarah M. Vorpahl, Samuel D. Stranks, Hirokazu Nagaoka, Giles E. Eperon, Mark E. Ziffer, Henry J. Snaith, and David S. Ginger Science Volume ():aaa5333 April 30, 2015 Published by AAAS

Fig. 1 Solar cell device measurement, bulk PL lifetime measurement, and correlated images from (SEM) and fluorescence microscopy experiments. Solar cell device measurement, bulk PL lifetime measurement, and correlated images from (SEM) and fluorescence microscopy experiments. (A) Light current-voltage (J-V) characteristics of a high-performing mixed halide perovskite solar cell. (B) Bulk time-resolved PL decay trace of CH3NH3PbI3(Cl) perovskite film on glass after excitation at 470 nm, 125 kHz, 30 nJ/cm2 (n0~1015cm−3) and fitted to a stretched-exponential function with <τ> = 1005 ns, (τc = 431 ns, β = 0.57), with nearly single-exponential dynamics at short times (inset). (C) Correlated SEM micrograph, (D) fluorescence image, and (E) composite image showing significant variations in PL intensity across different grains and grain boundaries. Dane W. deQuilettes et al. Science 2015;science.aaa5333 Published by AAAS

Fig. 2 Fluorescence microscopy of CH3NH3PbI3(Cl) film and local PL measurements. Fluorescence microscopy of CH3NH3PbI3(Cl) film and local PL measurements.(A) A 3 μm–by–3 μm fluorescence image of the perovskite film with bulk lifetime <τ> = 1010 ns (τc = 433 ns, β = 0.57). (B) Relative steady state PL spectra of bright (red square) and dark (blue circle) regions. (C) Time-resolved PL decay curves of bright (red square) and dark (blue circle) regions after excitation at 470 nm, 125 kHz, φ = 1 μJ/cm2 (n0 ~ 5 × 1016 cm−3), (D) φ = 2.1 μJ/cm2 (n0 ~ 1 × 1017cm−3), and (E) bright region measured at φ = 2.1 μJ/cm2 versus dark region measured at φ = 3.4 μJ/cm2 (n0 ~ 1.6 × 1017cm−3), showing that dark regions require higher initial carrier densities to exhibit kinetics dominated by bimolecular recombination. Black traces are simulations to the data (19). Dane W. deQuilettes et al. Science 2015;science.aaa5333 Published by AAAS

Fig. 3 Fluorescence microscopy of CH3NH3PbI3(Cl) film with pyridine vapor treatment. Fluorescence microscopy of CH3NH3PbI3(Cl) film with pyridine vapor treatment. (A) Fluorescence image before and (B) after treatment showing activation of the CH3NH3PbI3(Cl) film. (C) Bulk steady-state PL spectra showing the relative PL intensities before (blue circle) and after (red square) treatment (inset) and normalized spectra showing a slight blue shift and narrowing of full width at half maximum after treatment. (D) Grain boundary PL line scan before [blue line in (A)] and after [red line in (B)] treatment, showing slight relative reduction in PL quenching across the grain boundary after treatment. Dane W. deQuilettes et al. Science 2015;science.aaa5333 Published by AAAS

Fig. 4 Correlated images and line scans of CH3NH3PbI3(Cl) film using fluorescence microscopy, SEM, and EDS. (A) SEM micrograph overlaid on fluorescence image and (B) EDS line scan showing that the local elemental weight ratio of Cl/(Cl+I) tracks areas of higher integrated PL intensity, indicating that Cl is associated with better-performing grains. Correlated images and line scans of CH3NH3PbI3(Cl) film using fluorescence microscopy, SEM, and EDS.(A) SEM micrograph overlaid on fluorescence image and (B) EDS line scan showing that the local elemental weight ratio of Cl/(Cl+I) tracks areas of higher integrated PL intensity, indicating that Cl is associated with better-performing grains. Dane W. deQuilettes et al. Science 2015;science.aaa5333 Published by AAAS