SUPPLEMENTARY INFORMATION

Transcription

1 SUPPLEMENTARY INFORMATION Perovskite solar cells employing organic charge transport layers Olga Malinkiewicz, Aswani Yella, Yong Hui Lee, Guillermo Mínguez Espallargas, Michael Graetzel, Mohammad K. Nazeeruddin* and Henk J. Bolink* Instituto de Ciencia Molecular, Universidad de Valencia, C/ Catedrático J. Beltrán 2, Paterna (Valencia), Spain Laboratory of Photonics and Interfaces, Swiss Federal Institute of Technology (EPFL), Station 6, Lausanne, CH 1015, Switzerland Supporting Information Content: 1. Perovskite film sublimation, detailed process. (page 2) 2. Structural details of the perovskite films. (page 3) 3. Performance of large area solar cells. (page 5) nature photonics 1

2 supplementary information Perovskite film sublimation, detailed process. The sublimation of the perovskite was performed using a vacuum chamber of MBraun integrated in an inert glovebox (MBraun). Temperature controlled evaporation sources from Creaphys fitted with ceramic crucibles were employed to sublime the CH 3 NH 3 I and the PbI 2. The sources are directed upwards with an angle of approximately 90 with respect to the bottom of the evaporator. The substrates were placed at a distance of 20 cm from the top of the evaporation sources. Shutters are present at the evaporation sources and below the substrate holder. Three quartz microbalance sensors are present in the chamber, two monitoring the rate of each evaporation source and a third one at the height of the substrate holder. After the ceramic crucibles were loaded with the CH 3 NH 3 I and the PbI 2 the chamber was evacuated to a base pressure of 1*10-6 mbar. Fresh CH 3 NH 3 I was used for each evaporation. After the base pressure was reached, the CH 3 NH 3 I crucible was heated to 70 C. At this temperature, all three quartz sensors gave a signal. We were, however, unable to calibrate the sensor by measuring the thickness of a deposited CH 3 NH 3 I film. Therefore, an alternative process was used. Upon stabilization of the sensor reading the crucible containing the PbI 2 was heated. Only at PbI 2 evaporation temperatures in excess of 200 C were dark brown films obtained. The film thickness of the perovskite film was monitored using quartz sensor nr 3 (at the height of the substrate holder). Perovskite films were prepared at different PbI 2 evaporation temperatures, increasing with 10 degrees from the predetermined 200 C. In this way the optimum films were obtained at an evaporation temperature of the PbI 2 crucible of 250 C. 2 nature photonics

3 supplementary information Structural details of the perovskite films. As expected, the lower symmetry tetragonal phase is observed at room temperature (transition temperature to cubic phase = K) instead of the cubic phase. This transition is due to the more restricted motion of the methylammonium cation at lower temperatures, 1 which prevents the orientationally disorder needed for higher symmetry. In addition, this transition is accom- from panied by a tilting of the octahedrons around the c-axis with the change of space group Pm3m to I4/mcm. Figure S1. Two perpendicularr views of the crystal structure of the analogue CH 3 NH 3 SnI 3 per- ovskite, showing the tilting of the octahedrons. 2 1 Mitzi, D. B., Synthesis, Structure, and Properties of Organic-Inorganic Perovskites and Related Materials. In Progress in Inorganic Chemistry, vol. 48, John Wiley & Sons, Inc.: 1999, pp Y. Takahashi, R. Obara, Z.-Z Lin, Y. Takahashi, T. Naito, T. Inabe, S. Ishibashi and K. Ter- Dalton Trans., 40, 5563 (2011) akura. Charge-transport in tin-iodide perovskite CH3NH3SnI3C : origin of high conductivity. nature photonics 3

4 supplementary information The thin films are highly oriented along the (100), (010) and (001) directions, as evidenced in the powder patterns. Figure S2. Simulated X-ray powder pattern for CH 3 NH 3 PbI 3 with no preferred orientation (green), with preferred orientation along the (001) direction (pink), along the (100) or (010) directions (orange), along the (100), (010) and (001) directions (black) and observed (blue). The peaks at 30.5 and 35.5 in the observed pattern correspond to the ITO substrate. Figure S3. Observed (blue) and calculated (red) profiles and difference plot [(I obs I calcd )] (green) of the X-ray powder diffraction Pawley refinement for CH 3 NH 3 PbI 3 ( = Cu K 1, 2 range ). Tick marks indicate peak positions for compound CH 3 NH 3 PbI 3. The peaks at 30.5 and 35.5 correspond to the ITO substrate. 4 nature photonics

5 supplementary information Performance of large area solar cells. Photocurrent density [ma/cm 2 ] dark 100% 50% 10% IPCE [%] IPCE Voltage [V] Wavelength [nm] Figure S4. J-V and IPCE characteristics of the large area (0.98 cm 2 ) peroskite solar cell. (a) Photocurrent density versus voltage at 100, 50 and 10 mw cm 2 and in the dark. (b) IPCE spectrum and absorbance of a 285 nm thick perovskite layer. nature photonics 5