Shanghai Institute of Ceramics, Chinese Academy of Sciences, Dingxi, 1295, Changning,

Transcription

1 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, , China b University of Chinese Academy of Sciences, Yuquan 19, Shijingshan, Beijing, , China c CAS Key Laboratory of Materials for Energy Conversion, Shanghai Instute of Ceramics, Chinese Academy of Sciences, Heshuo 588, Jiading, Shanghai, , China d National Institute of Advanced Industrial Science and Technology (AIST), Moriyama, Nagoya , Japan leilei@mail.sic.ac.cn; caoxun2015@gmail.com; p-jin@mail.sic.ac.cn S-1

2 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 Pa and the work pressure was around 1.5 Pa. DC magnetron sputtering was conducted at 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

3 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

4 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 (S BQ). 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

5 voltage bias with a scan rate of 40 mv/s. S-5

6 Figure S1. The XRD pattern of perovskite film on {001} dominated TiO 2 film. S-6

7 Figure S2. Cross section FESEM image of {001} dominated TiO 2 film. S-7

8 Figure S3. The top view FESEM image of perovskite film on {001} dominated TiO 2 film. S-8