Hole Selective NiO Contact for Efficient Perovskite Solar Cells with Carbon Electrode

Transcription

1 Supporting information For Nano Letters Hole Selective NiO Contact for Efficient Perovskite Solar Cells with Carbon Electrode Xiaobao Xu,,, Zonghao Liu,, Zhixiang Zuo, Meng Zhang, Zhixin Zhao, Yan Shen, Huanping Zhou, Qi Chen, Yang Yang, Mingkui Wang * Michael Grätzel Centre for Mesoscopic Solar Cells, Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, Hubei , P. R. China Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, USA Corresponding author: M.W: mingkui.wang@mail.hust.edu.cn Method Carbon electrode: The carbon black paste was prepared as following: 5 g graphite (8000 mesh), 1 g carbon black powder (particle size: 30 nm) and 1 g ZrO 2 (particle size: 20 nm) was added in 30 ml terpilenol followed by 10 hours of ball milling. Devices Fabrication: The FTO glass plates (3 mm thickness, 7 Ω/, Nippon Sheet Glass) were cleaned in detergent using a ultrasonic bath for 15 min and then rinsed with deionized water and ethanol for 15 min, respectively. To make a dense TiO 2 blocking layer, the cleaned FTO glasses were coated with ethanol solution containing titanium diisopropoxide bis(acetylacetonate) (v:v, 9:1). With a doctor-blade 1

2 technique, a TiO 2 layer was fabricated on FTO glass with compact layer and ZrO 2 layer was prepared on the top of the mesoporous TiO 2 film. Following heating the paste in the air flow with a procedure of 112 o C for 5 min, 175 o C for 5 min, 350 o C for 10 min, 400 o C for 15 min, and then 500 o C for 30 min. The TiO 2 layer and ZrO 2 layer were finally confirmed by Profile-system (DEKTAK 150, VECCO, Bruker) to be 480 nm, respectively. The NiO layer was deposited accordingly. The carbon paste was blade coated on the dry film, and then sintered in air at 400 o C for 20 min. The prepared blank cell was coated with 25 μl of 450 mg PbI 2 in DMF solution, followed by heating at 70 o C for 30 min, and then immersed in 8 mg CH 3 NH 3 I in IPA solution for 10 min. Photovoltaic Characterization: A 450 W xenon light source solar simulator (Oriel, model 9119) with AM 1.5G filter (Oriel, model 91192) was used to give an irradiance of 100 mw cm -2 at the surface of the solar cell. The current-voltage characteristics of the cell under these conditions were obtained by applying external potential bias to the cell and measuring the generated photocurrent with a Keithley model 2400 digital source meter. A similar data acquisition system was used to control the IPCE measurement. A white light bias (1% sunlight intensity) was applied onto the sample during the IPCE measurements with ac model (10 Hz). Electronic impedance spectroscopy (IS) measurement: IS measurements were measured using the PGSTAT302N frequency analyzer from Autolab (Eco Chemie B.V, Utrecht, The Netherlands) together with the Frequency Response Analyzer module providing voltage modulation in the desired frequency range. The Z-view software (v2.8b, Scribner Associates Inc.) was used to analyze the impedance data. The EIS experiments were performed at a constant temperature of 25 o C in the dark. The impedance spectra of the MAPbI 3 -based devices were recorded at potentials varying from -1.0 V to 0 V at frequencies ranging from 0.01 Hz to 1 MHz, the oscillation potential amplitudes being adjusted to 10 mv. The photoanode (FTO attached with TiO 2 ) was used as the working electrode and counter electrode (CE) was used as both the auxiliary electrode and the reference electrode. 2

3 Table S1 Effect of film thickness on short-circuit photocurrent density (J SC ), open-circuit voltage (V OC ), fill factor (FF), and conversion efficiency (η) for the devices. TiO 2 /nm ZrO 2 /nm NiO/nm V OC [mv] J SC [ma cm -2 ] FF PCE [%] 480±30 500± ±30 500± ±30 500± ±30 300± ±30 600± ±30 900± ±30 500±30 480± ±30 500±30 600±

4 Figure S1. BET measurements for a) TiO 2 and b) NiO mesoporous films. 4

5 Figure S2. The equivalent circuit for fitting of electronic impedance spectroscopy under illumination 5

6 1 / C 2 (a.u.) U / V Figure S3. Mott-Schottky analysis of device A with TiO 2 /ZrO 2 /carbon(mapbi 3 ) configuration. 6

7 TiO 2 CB CB VB VB NiO CH 3 NH 3 PbI Figure S4. Energy level of different materials used in this study. 7

8 Figure S5. Electronic impedance spectroscopy characteristics of the three devices in dark. Electronic impedance spectrum in the form of Nyquist plot (left) and Bode phase plot (right) for device A TiO 2 /ZrO 2 /carbon(mapbi 3 ) (black), device B TiO 2 /NiO/carbon(MAPbI 3 ) (red), and device C TiO 2 /ZrO 2 /NiO/carbon(MAPbI 3 ) (blue) measured in the dark with a bias at a) -0.8 V, b) V, and c) -0.3 V. 8

9 10 3 a) in dark 10-3 b) in dark c) in dark 10-2 R ct 1 / Ω cm U / V C1 / F Devica A U / V τ e / s U / V Figure S6. Derived Equivalent circuit components obtained from impedance measurements in dark conditions for three different devices: Electronic parameters a) the recombination resistance R ct 1 at the MAPbI 3 /TiO 2 interface, b) the corresponding capacitance C1, and c) the charge lifetime τ e 1 obtained from fitting the impedance spectrum in the form for device A TiO 2 /ZrO 2 /carbon(mapbi 3 ) (black), device B TiO 2 /NiO/carbon(MAPbI 3 ) (red), and device C TiO 2 /ZrO 2 /NiO/carbon(MAPbI 3 ) (blue) measured in the dark. 9

10 10 1 (a) 10 1 (b) 10 1 (c) C' / F cm Frequency / Hz C ' / F cm Frequency / HZ C' / F cm Frequency / Hz Figure S7. Bode plots of capacitance obtained from the impedance spectroscopy measured under illumination for different devices at a) -0.8V, b)-0.55v, and c)-0.3v, respectively. 10

11 Normalized efficiency (a.u.) aged in dark at RT aged in dark at 60 0 C aged under illumiation (0.7 sun intensity) at 40 0 C t / hrs Figure S8 (a) Stability investigation on perovskite solar cell device with TiO 2 /ZrO 2 /NiO/carbon(MAPbI 3 ) configuration under different test conditions, including storing at room temperature without light soaking (black), storing at 60 o C without light soaking (red), and exposure to AM 1.5 simulated sunlight (0.7 sun) with a temperature at 45 o C (blue). 11