Supporting Information for Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room Temperature DC Magnetron Sputtered TiO 2 Electron Extraction Layer Aibin Huang, a,b Lei Lei, a* Jingting Zhu, a,b Yu Yu, a,b Yan Liu, a Songwang Yang, c Shanhu Bao, a Xun Cao, a* and Ping Jin a,d* a State Key Laboratory of High Performance Ceramics and superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Dingxi, 1295, Changning, Shanghai, 200050, China b University of Chinese Academy of Sciences, Yuquan 19, Shijingshan, Beijing, 100049, China c CAS Key Laboratory of Materials for Energy Conversion, Shanghai Instute of Ceramics, Chinese Academy of Sciences, Heshuo 588, Jiading, Shanghai, 201899, China d National Institute of Advanced Industrial Science and Technology (AIST), Moriyama, Nagoya 463-8560, Japan E-mail: leilei@mail.sic.ac.cn; caoxun2015@gmail.com; p-jin@mail.sic.ac.cn S-1
Experimental Section Preparation of TiO 2 compact layer on FTO substrates FTO glass used as transparent conductive electrode were ultrasonically cleaned by acetone, ethanol and deionized water successively for 30 minutes and then dried by flowing N 2 gas. The film was directly deposited on FTO glass by a DC reactive magnetron sputtering system (Shenyang Teng Ao Vacuum Technology Co. Ltd., JSS-600) with a titanium target (99.99 % purity) at room temperature. The angle between the target and the substrate was fixed at 37 o and rotation speed of the substrate was kept at 15 rpm during the deposition process. The base pressure of the deposition chamber was kept at 4 10-4 Pa and the work pressure was around 1.5 Pa. DC magnetron sputtering was conducted at 600-750 W and a fixed hybrid gas composed of 35 sccm Ar and 5 sccm O 2 was imported. By adjusting the work pressure, sputtering power and gas ratio, the film thickness of TiO 2 films can be regulated. Prior to the deposition process, the Ti target was pre-sputtered for 10 min in order to eliminate the residual oxide layer. Synthesis of CH 3 NH 3 I powder Methylamine iodide (CH 3 NH 3 I) was synthesized and purified on the basis of a reported method. 30 ml methylamine (33% wt in ethanol, Sigma-Aldrich) and 28 ml hydroiodic acid (57% in water, Sigma-Aldrich) reacted in a 250 ml round-bottomed flask at 0 С in an ice bath for 2 h with stirring. The solvent was then removed with a rotary evaporator by heating the solution at 60 С under reduced pressure, and the precipitate was then S-2
crystallized. The product was washed with diethyl ether for three times, and then dissolved in ethanol, recrystallized using diethyl ether, and finally dried in a vacuum at 60 С for 24 h to yield CH 3 NH 3 I. Fabrication of perovskite solar cells Mesostructured perovskite solar cells were fabricated on FTO glass substrates. The CH 3 NH 3 PbI 3 film around 500 nm was prepared with a reported method. Firstly, PbI 2 (Aladdin, 99.8 %) was dissolved in anhydrous N,N-dimethylformamide (DMF, SCRC, 99.5 %) and stirred at room temperature for 1h (578 mg/ml), and spin coated onto the TiO 2 surface at 6500 rpm for 5 s. The substrates were then dried on a 90 С hotplate for 2 min to remove the remaining solvent. After that, the film was faced down at a constant distance of around 3 mm against the pre-synthesized CH 3 NH 3 I powder. The reaction was conducted in a vacuum oven under the pressure of 100 Pa at 110 С for 6.5 h and then the film was rinsed with isopropanol for 45 s followed by drying with pressurized air. Thereafter, a hole-transporting layer was deposited onto the perovskite film by spin coating at 4000 rpm for 30 s. The hybrid solution contained 72.3 mg spiro-ometad (Merk), 1 ml chlorobenzene (Sigma Aldrich), 17.5 µl lithium-bis(trifluoromethanesulfonyl)imide (Li-TFSI, J&K scientific Ltd.) solution (520 mg cm -3 Li-TFSI in 1mL acetonitrile) and 28.5 µl 4-tert-butylpyridine (TBP, Sigma Aldrich). Finally, 80 nm-thick silver acting as the counter electrode was thermally evaporated on top of the hole transporting layer through a metal shadow mask, with an S-3
active area of 0.07 cm 2 Device characterization Scanning electron microscopy (SEM) was investigated on a field emission scanning electron microscope (FEI, Magellan 400). X-ray diffraction (XRD) measurements were performed with an Ultima IV X-ray diffractometer using Cu Kα radiation under operation conditions of 40 kv and 40 ma, with a scanning speed of 5 per minute. The UV vis transmittance spectra of TiO 2 film were recorded on UV-Vis spectrophotometer (HITACHI U-3010). Steady photoluminescence (PL) measurements were conducted at room temperature on a Horiba-Ltd. FluoroMax-4 device with an excitation wavelength of 470 nm. Time-resolved PL spectra were measured using a fluorescence lifetime spectrometer (Photo Technology International, Inc.). The PL lifetime of the CH 3 NH 3 Pb 3 I films on TiO 2 /FTO glass substrates were calculated by fitting the experimental decay transient data to the bi-exponential decay model. Incident photon-to-current conversion efficiency (IPCE) was measured on a SM-250 system (Bunkoh-keiki, Japan). The intensity of monochromatic light was measured with a Si photodiode (S1337-1010BQ). Current voltage characteristics of solar cells were measured under simulated AM1.5G illumination of 100 mw/cm 2 with a Keithley-2420 source meter in combination with a Sol3A class AAA solar simulator IEC/JIS/ASTM equipped with an AM1.5G filter and a 450 W xenon lamp. The light intensity was calibrated with a reference silicon solar cell (Oriel-91150). The J V curves were respectively measured by applying an external S-4
voltage bias with a scan rate of 40 mv/s. S-5
Figure S1. The XRD pattern of perovskite film on {001} dominated TiO 2 film. S-6
Figure S2. Cross section FESEM image of {001} dominated TiO 2 film. S-7
Figure S3. The top view FESEM image of perovskite film on {001} dominated TiO 2 film. S-8