Hybrid Halide Perovskite Solar Cell Precursors: The Colloidal ...
Hybrid Halide Perovskite Solar Cell Precursors: The Colloidal Chemistry and Coordination Engineering behind Device Processing for High Efficiency Keyou Yan,†, ‡,║,* Mingzhu Long, †,║ Tiankai Zhang, † Zhanhua Wei, ‡ Haining Chen, ‡ Shihe Yang, ‡,*
†
Jianbin Xu†,*
Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
‡
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
*Corresponding author. ║
E-mail: [email protected]; [email protected]; [email protected]
These authors contribute equally to this work.
KEYWORDS · Perovskite Precursor · Colloidal Chemistry · Coordination Complex ·Solar Cell · High Efficiency ·
S1
EXPERIMETAL SECTION Material synthesis and preparation: CH3NH3I and CH3NH3Cl were synthesized in an ice bath for 2 hrs by reacting methylamine (CH3NH2, 33 wt% in ethanol from Sigma-Aldrich) with hydroiodic acid (HI, 57 wt% in water from Sigma-Aldrich) and hydrochloric acid (HCl, 37 wt% in water from Sigma-Aldrich), separately. The white powders were collected by heating at 50°C and washed for 3 times with diethyl ether (Sigma-Aldrich). Lead iodide was prepared at 1 M concentration in anhydrous N,N-Dimethylformamide (DMF, 99.8%, Sigma-Aldrich) and filtrated though a 0.2 µm PTFE filter as stock solution at 70°C. Precursors with different organic inorganic ratios were prepared by sequentially adding of 1mL stock solution
(99.9%, Sigma-Aldrich) and CH3NH3I (or
CH3NH3Cl) into 0.5mL DMF solution, with fixed concentration of lead iodide at 0.75 M and tunable organic inorganic ratio of CH3NH3I:PbI2 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1 and CH3NH3Cl:CH3NH3I:PbI2 0.5:1:1, 1:1:1, 1.5:1:1, 2:1:1 for solar cells. Fabrication of Planar Version Solar Cells: Solar cells were fabricated as follows: FTO (substrates were sequentially cleaned with deionized water, acetone, 2-propanol for 30 mins each. A compact TiO2 blocking layer was deposited on cleaned FTO by spin-coating a mildly acidic solution of titanium isopropoxide (97%, Sigma-Aldrich) in ethanol (consisting of 1 mL titanium isopropoxide and 0.15 mL 37% HCl solution in14.5 ml ethanol) at 5000 rpm for 40s, and annealed at 500°C for 45 min in an oven. After the substrates were cooled to room temperature, the perovskite precursor solution was spin-coated at 2500 r.p.m. for 40 s. After drying for more than 10 mins, the as-prepared films were annealed for 25, 40, 60, 80 mins at 100°C in the case of CH3NH3Cl:CH3NH3I:PbI2 0.5:1:1, 1:1:1, 1.5:1:1, 2:1:1, and 10 min, 15min, 30min at 100°C in the cases of CH3NH3I:PbI2 0.5:1, 1:1, 1.5:1, 5min, 15min, 30min at 150°C for CH3NH3I:PbI2 2:1, 2.5:1, 3:1. After cooling down, the perovskite films are subjected to 20 min calcination at 100°C with a cover glass atop. A volume of 35 µL of spiro-MeOTAD solution was spin-coated on the CH3NH3PbI3 perovskite layer at 5,000 r.p.m. for 30 s. A spiro-MeOTAD solution was prepared by dissolving 60 mg of spiro-MeOTAD in 1 ml of chlorobenzene, to which 30 µl of 4-tert-butyl pyridine and 20 µl of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) solution (520 mg LI-TSFI in 1 ml acetonitrile, Sigma-Aldrich, 99.8%) were added. Finally, 80 nm of gold was thermally evaporated on the spiro-MeOTAD-coated film. Material and device Characterizations: UV-Vis absorption spectra were taken on a Hitachi S2
U-3501 ultraviolet/visible/near-infrared spectrophotometer. NanoBrook Omni Particle Size Analyzer was employed to detect the size distribution. Morphological images of the perovskite films were observed by HR-FESEM (FEI, Quanta 400). The crystalline structures for the perovskite films were characterized by XRD (Rigaku, Smart Lab). Sample thicknesses were measured using an Alpha Step 500 Surface profiler. The current density–voltage (J-V) curves were measured (Keithley Instruments, 2612 Series Source Meter) under simulated AM 1.5 sunlight at 100 mW cm-2 irradiance generated by a 94011A-ES Sol series Solar Simulator.
Table 1. J-V curves of perovskite solar cells based on perovskite thin films.
Samples 0.5:1
1:1
1.5:1
2:1
2.5:1
3:1
0.5:1:1
1:1:1
1.5:1:1
2:1:1
Scan direction
Voc (V)
Jsc (mA cm-2)
FF
PCE
Forward
0.821
12.63
0.329
3.31%
Reverse
0.860
14.26
0.441
5.41%
Forward
0.871
16.86
0.433
6.36%
Reverse
0.932
17.50
0.555
9.05%
Forward
0.812
12.46
0.384
3.89%
Reverse
0.855
13.32
0.533
6.07%
Forward
0.809
11.87
0.386
3.71%
Reverse
0.855
13.12
0.527
5.91%
Forward
0.641
9.42
0.270
1.63%
Reverse
0.671
11.16
0.333
2.49%
Forward
0.661
5.60
0.232
0.86%
Reverse
0.663
6.50
0.274
1.18%
Forward
0.866
18.86
0.53
8.67%
Reverse
0.883
19.10
0.61
10.30%
Forward
1.06
21.63
0.643
14.75%
Reverse
1.08
21.68
0.653
15.29%
Forward
1.02
19.08
0.579
11.26%
Reverse
1.07
19.29
0633
13.06%
Forward
0.93
19.16
0.525
9.35%
Reverse
1.03
19.33
0.650
12.95%
S3
Average PCE
4.36%
7.71%
4.98%
4.81%
2.06%
1.02%
9.47%
15.01%
12.16%
11.15%
Figure S1. The typical Tyndall effect of the colloidal solution composed of the perovskite precursor with different reagent ratios (from left to right: 0.5: 1; 1:1; 1.5:1; 2:1; 2.5:1 and 3:1) (A) The as-prepared precursor solution; (B) The Tyndall effects under light; (C) The Tyndall effects in the dark.
S4
Figure S2. Bottom-up analysis of perovskite colloidal soft framework, which is actually corner-shared octahedral soft framework (denoted as [- PbIx -…- PbIx -]n) and MA (green) is not sterically arranged for lattice at this stage due to its higher solubility. formation process.
S5
Notes: it’s not the real
Figure S3. The as-prepared perovskite precursor films at different precursor ratio before (A) and after calcination (B).
S6
Figure S4. The as-prepared perovskite thin films at different precursor ratio after calcination. Scanning electron microscopy (SEM) micrographs and enlarged views at (A) 0.5: 1; (B) 1:1; (C) 1.5:1; (D) 2:1; (E) 2.5:1; and (F) 3:1 of CH3NH3I: PbI2.
S7
Figure S5. The as prepared perovskite thin films at different precursor ratio after calcination. SEM micrographs and enlarged views at (A) 0.5:1:1; (B) 1:1:1; (C) 1.5:1:1; and (D) 2:1:1 of CH3NH3Cl: CH3NH3I: PbI2.
S8
1.0
Weight (100%)
0.8 0.6 0.4 0.2 0.0 100
CH3NH3Cl CH3NH3Br CH3NH3I
150
200 250 300 Temperature (°C)
350
Figure S6. Thermogravimetric analysis of CH3NH3X (X=Cl, Br, I).
S9
400
†
Jianbin Xu†,*
Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
‡
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
*Corresponding author. ║
E-mail: [email protected]; [email protected]; [email protected]
These authors contribute equally to this work.
KEYWORDS · Perovskite Precursor · Colloidal Chemistry · Coordination Complex ·Solar Cell · High Efficiency ·
S1
EXPERIMETAL SECTION Material synthesis and preparation: CH3NH3I and CH3NH3Cl were synthesized in an ice bath for 2 hrs by reacting methylamine (CH3NH2, 33 wt% in ethanol from Sigma-Aldrich) with hydroiodic acid (HI, 57 wt% in water from Sigma-Aldrich) and hydrochloric acid (HCl, 37 wt% in water from Sigma-Aldrich), separately. The white powders were collected by heating at 50°C and washed for 3 times with diethyl ether (Sigma-Aldrich). Lead iodide was prepared at 1 M concentration in anhydrous N,N-Dimethylformamide (DMF, 99.8%, Sigma-Aldrich) and filtrated though a 0.2 µm PTFE filter as stock solution at 70°C. Precursors with different organic inorganic ratios were prepared by sequentially adding of 1mL stock solution
(99.9%, Sigma-Aldrich) and CH3NH3I (or
CH3NH3Cl) into 0.5mL DMF solution, with fixed concentration of lead iodide at 0.75 M and tunable organic inorganic ratio of CH3NH3I:PbI2 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1 and CH3NH3Cl:CH3NH3I:PbI2 0.5:1:1, 1:1:1, 1.5:1:1, 2:1:1 for solar cells. Fabrication of Planar Version Solar Cells: Solar cells were fabricated as follows: FTO (substrates were sequentially cleaned with deionized water, acetone, 2-propanol for 30 mins each. A compact TiO2 blocking layer was deposited on cleaned FTO by spin-coating a mildly acidic solution of titanium isopropoxide (97%, Sigma-Aldrich) in ethanol (consisting of 1 mL titanium isopropoxide and 0.15 mL 37% HCl solution in14.5 ml ethanol) at 5000 rpm for 40s, and annealed at 500°C for 45 min in an oven. After the substrates were cooled to room temperature, the perovskite precursor solution was spin-coated at 2500 r.p.m. for 40 s. After drying for more than 10 mins, the as-prepared films were annealed for 25, 40, 60, 80 mins at 100°C in the case of CH3NH3Cl:CH3NH3I:PbI2 0.5:1:1, 1:1:1, 1.5:1:1, 2:1:1, and 10 min, 15min, 30min at 100°C in the cases of CH3NH3I:PbI2 0.5:1, 1:1, 1.5:1, 5min, 15min, 30min at 150°C for CH3NH3I:PbI2 2:1, 2.5:1, 3:1. After cooling down, the perovskite films are subjected to 20 min calcination at 100°C with a cover glass atop. A volume of 35 µL of spiro-MeOTAD solution was spin-coated on the CH3NH3PbI3 perovskite layer at 5,000 r.p.m. for 30 s. A spiro-MeOTAD solution was prepared by dissolving 60 mg of spiro-MeOTAD in 1 ml of chlorobenzene, to which 30 µl of 4-tert-butyl pyridine and 20 µl of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) solution (520 mg LI-TSFI in 1 ml acetonitrile, Sigma-Aldrich, 99.8%) were added. Finally, 80 nm of gold was thermally evaporated on the spiro-MeOTAD-coated film. Material and device Characterizations: UV-Vis absorption spectra were taken on a Hitachi S2
U-3501 ultraviolet/visible/near-infrared spectrophotometer. NanoBrook Omni Particle Size Analyzer was employed to detect the size distribution. Morphological images of the perovskite films were observed by HR-FESEM (FEI, Quanta 400). The crystalline structures for the perovskite films were characterized by XRD (Rigaku, Smart Lab). Sample thicknesses were measured using an Alpha Step 500 Surface profiler. The current density–voltage (J-V) curves were measured (Keithley Instruments, 2612 Series Source Meter) under simulated AM 1.5 sunlight at 100 mW cm-2 irradiance generated by a 94011A-ES Sol series Solar Simulator.
Table 1. J-V curves of perovskite solar cells based on perovskite thin films.
Samples 0.5:1
1:1
1.5:1
2:1
2.5:1
3:1
0.5:1:1
1:1:1
1.5:1:1
2:1:1
Scan direction
Voc (V)
Jsc (mA cm-2)
FF
PCE
Forward
0.821
12.63
0.329
3.31%
Reverse
0.860
14.26
0.441
5.41%
Forward
0.871
16.86
0.433
6.36%
Reverse
0.932
17.50
0.555
9.05%
Forward
0.812
12.46
0.384
3.89%
Reverse
0.855
13.32
0.533
6.07%
Forward
0.809
11.87
0.386
3.71%
Reverse
0.855
13.12
0.527
5.91%
Forward
0.641
9.42
0.270
1.63%
Reverse
0.671
11.16
0.333
2.49%
Forward
0.661
5.60
0.232
0.86%
Reverse
0.663
6.50
0.274
1.18%
Forward
0.866
18.86
0.53
8.67%
Reverse
0.883
19.10
0.61
10.30%
Forward
1.06
21.63
0.643
14.75%
Reverse
1.08
21.68
0.653
15.29%
Forward
1.02
19.08
0.579
11.26%
Reverse
1.07
19.29
0633
13.06%
Forward
0.93
19.16
0.525
9.35%
Reverse
1.03
19.33
0.650
12.95%
S3
Average PCE
4.36%
7.71%
4.98%
4.81%
2.06%
1.02%
9.47%
15.01%
12.16%
11.15%
Figure S1. The typical Tyndall effect of the colloidal solution composed of the perovskite precursor with different reagent ratios (from left to right: 0.5: 1; 1:1; 1.5:1; 2:1; 2.5:1 and 3:1) (A) The as-prepared precursor solution; (B) The Tyndall effects under light; (C) The Tyndall effects in the dark.
S4
Figure S2. Bottom-up analysis of perovskite colloidal soft framework, which is actually corner-shared octahedral soft framework (denoted as [- PbIx -…- PbIx -]n) and MA (green) is not sterically arranged for lattice at this stage due to its higher solubility. formation process.
S5
Notes: it’s not the real
Figure S3. The as-prepared perovskite precursor films at different precursor ratio before (A) and after calcination (B).
S6
Figure S4. The as-prepared perovskite thin films at different precursor ratio after calcination. Scanning electron microscopy (SEM) micrographs and enlarged views at (A) 0.5: 1; (B) 1:1; (C) 1.5:1; (D) 2:1; (E) 2.5:1; and (F) 3:1 of CH3NH3I: PbI2.
S7
Figure S5. The as prepared perovskite thin films at different precursor ratio after calcination. SEM micrographs and enlarged views at (A) 0.5:1:1; (B) 1:1:1; (C) 1.5:1:1; and (D) 2:1:1 of CH3NH3Cl: CH3NH3I: PbI2.
S8
1.0
Weight (100%)
0.8 0.6 0.4 0.2 0.0 100
CH3NH3Cl CH3NH3Br CH3NH3I
150
200 250 300 Temperature (°C)
350
Figure S6. Thermogravimetric analysis of CH3NH3X (X=Cl, Br, I).
S9
400
