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Thereafter, an electron-transporting material ([6,6]-phenyl-C61-butyric acid methyl ester (PCBM)) was deposited onto the perovskite film by spin coating at 4000 ...

Supporting Information for Enhance d electrical property of Ni-doped CoOx hole transport layer for high performance perovskite solar cells Aibin Huang1,2 , Lei Lei1 *, Yu Yu1,2 , Yan Liu1 , Songwang Yang3 , Shanhu Bao1 , Xun Cao1 *, and Ping Jin 1,2 * 1

State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai institute of Ceramics, Chinese Academy of Sciences, Dingxi 1295, Changning, Shanghai, 200050, China 2 University of Chinese Academy of Sciences, Yuquan 19, Shijingshan, Beijing, 100049, China 3 CAS Key Laboratory of Materials for Energy Conversion, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Heshuo 588, Jiading, Shanghai, 201899, China. 4 National Institute of Advanced Industrial Science and Technology (AIST), Moriyama, Nagoya 463-8560, Japan E-mail: [email protected], [email protected], [email protected] Keywords: magnetron sputtering, Ni-doped CoOx , hole transport material, perovskite solar cell

Experimental Section Preparation of CoOx HTLs on FTO substrates Transparent conductive electrode FTO glass were ultrasonically cleaned by acetone, ethanol and deionized water successively for 30 minutes and then dried by air flow. A direct current (DC) reactive magnetron sputtering system (Shenyang Tengao Vacuum Technology Co.Ltd.,JSS-600) with Cobalt and Nickel target (99.99% purity) was used to deposit CoOx with or without Ni doping at room temperature. In our experiment, the angle between the target and the substrate was located at 37o and substrate rotation speed was 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 2 Pa. DC magnetron sputtering was conducted with a fixed hybrid gas composed of 24 sccm Ar and 12 sccm O2 flow rates. By adjusting the work pressure and sputtering power, the distinctive films could be obtained with certain thickness. Prior to the deposition process, the Co and Ni target was pre-sputtered for 10 min in order to eliminate the residual oxide layer. Fabrication of perovskite solar cells Planar heterojunction perovskite solar cells were fabricated on FTO glass substrates. The CH3 NH3 PbI3 film around 300 nm was prepared with a precursor solution containing 1.383 g PbI2 (Sigma-Aldrich, 99 %), 0.477 g CH3 NH3 I (TCI, 99 %), 0.213 mL diethyl sulphoxide (DMSO, Sigma-Aldrich, 99%) and 1.905 mL anhydrous N,N-dimethylformamide (DMF, Sigma-Aldrich, 99%). 30 μL perovskite solution was casted on CoOx film at 3000 rpm, during which 0.5 mL ethyl ether was continuously dripped. The dripping started at 7 s after the substrate rotation and the duration was about 2 s. Thereafter, an electron-transporting material ([6,6]-phenyl-C61-butyric acid methyl ester (PCBM)) was deposited onto the perovskite film by spin coating at 4000 rpm for 30 s. Finally, 120 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 active area of 0.07 cm2 . Device characterization Scanning electron microscopy (SEM) was conducted with a field emission scanning electron microscope (FEI, Magellan 400). The surface state of the films were checked with an atomic force microscopy (AFM, SII Nano Technology Ltd., Nanonavi) in noncontact mode. The valence state and valence band spectrum of the cobalt oxide films with and without nickel doping were analyzed by X-ray photoelectron spectroscopy (XPS) with monochromatic Al Kα radiation at a pass energy of 29.4 eV. The UV-vis transmittance spectra of TiO2 film were recorded on an 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 457 nm. Time-resolved PL spectra were measured using a fluorescence lifetime spectrometer (Photo Technology International, Inc.). The PL lifetime of the CH3 NH3 PbI3 films on Ni:CoOx /FTO glass substrates were calculated by fitting the experimental decay data with bi-exponential decay

model. Current density- 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 voltage bias with a scan rate of 40 mV/s. 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).

Figure S1. (A) the transmittance of CoOx prepared with different precursor concentration, (B) J-V characteristics of perovskite solar cells based on CoOx prepared with different precursor concentration and top view morphology of CoOx film with a precursor concentration of (C) 0.1 M and (D) 0.3 M.

Figure S2. Top view image of magnetron sputtered CoOx film.

Figure S3 XPS valence band spectrum for the CoOx film.

Figure S4 Optical absorption coefficient α as a function of incident photon energy for indirect allowed transition for CoOx . The intercept of extrapolated straight line indicated the corresponding direct band gap.

Figure S5 Schematic view of the device structure.

Figure S6 The PCEs distribution histogram of 20 PSCs based on Ni: CoOx HTL

Figure S7 Normalized power conversion efficiency based on CoOx , Ni: CoOx and PEDPT:PSS HTLS as a function of storage under special condition.