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Article

Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells

by
Takeo Oku
1,*,
Shoma Uchiya
1,
Riku Okumura
1,
Atsushi Suzuki
1,
Iori Ono
1,
Sakiko Fukunishi
2,
Tomoharu Tachikawa
2 and
Tomoya Hasegawa
2
1
Department of Materials Science, The University of Shiga Prefecture, 2500 Hassaka, Hikone 522-8533, Shiga, Japan
2
Osaka Gas Chemicals Co. Ltd., 5-11-61 Torishima, Konohana-ku 554-0051, Osaka, Japan
*
Author to whom correspondence should be addressed.
Inorganics 2023, 11(7), 273; https://doi.org/10.3390/inorganics11070273
Submission received: 31 March 2023 / Revised: 22 June 2023 / Accepted: 23 June 2023 / Published: 27 June 2023
(This article belongs to the Section Inorganic Materials)
Browse Figures
Versions Notes

Abstract

:
The effects of guanidinium (C(NH2)3, GA) and cesium (Cs) co-additions on methylammonium lead iodide (CH3NH3PbI3, MAPbI3) perovskite solar cells were investigated. The first-principles calculations on the density of the states and band structures showed a reduction in the total energy by the GA addition. Although the calculation showed that the co-addition of the GA/Cs to the MAPbI3 perovskite could decrease the carrier mobilities, and the addition of GA/Cs improved the device performance. This result would be due to a facilitation of grain growth and a suppression of the defects from the GA/Cs addition. The changes to the conversion efficiencies of the device with the best performance were small, which indicates that the present co-addition of GA/Cs is effective for the stability of the devices.

Graphical Abstract

1. Introduction

Perovskite solar cells are expected to be the next-generation solar cells. Perovskite crystals represented by a composition ABX3 are used as the photovoltaic materials, and CH3NH3PbI3 (MAPbI3) has been widely used for the perovskite solar cells [1,2,3,4]. Although the perovskite compounds have tunable band gaps and an easy fabrication process, the MAPbI3 is unstable in air because of the migration and desorption of methylammonium (CH3NH3, MA) molecules at the A-site [5,6,7,8]. Therefore, the MA ions have been substituted with organic or inorganic cations, and the power conversion efficiencies and durability of the devices have been improved with the A-site engineering [9,10].
To stabilize the perovskite structures, various cations such as formamidinium (HC(NH2)2, FA) [11,12], ethylammonium (CH3CH2NH3, EA) [13,14], or guanidinium (C(NH2)3, GA) [15,16,17,18], which have larger ionic radii than MA, have been introduced at the MA site, and their stabilities were improved to a certain extent. The introduction of alkali metals such as cesium (Cs) [19,20,21], rubidium (Rb) [22,23,24], potassium (K) [25,26,27,28], and sodium (Na) [29,30,31] was also effective since these alkali elements do not desorb from the perovskite compounds.
Recently, various types of GA-added perovskite compounds have been investigated as solar cell materials. The carrier lifetime and the surface morphology were improved by introducing guanidinium bromide (GABr) in MAPbI3. The conversion efficiency of the device with 10% GABr showed less hysteresis than that of MAPbI3 [32], and the conversion efficiency was stable after a continuous irradiation of light for 400 h. The dynamics of multiple organic cations, including GA, were also discussed quantitatively [33], which indicated that relationship between organic cations and perovskite properties could provide a guideline for the high-efficiency perovskite solar cells. The effects of a surface treatment with guanidinium iodide (GAI) were also reported [34], which showed that the treatment with 10 mg mL−1 GAI solution removed excess PbI2 and the crystallinity and grain sizes were improved. Other approaches such as microstructural control and surface passivation have been reported [35,36,37,38,39,40,41], in addition to the GA addition to the perovskite precursor solutions.
A-site cation engineering with inorganic cations has also been actively investigated. Compact and homogeneous perovskite films were obtained by adding Cs chloride to perovskite precursor solutions, and the device performance was improved [42]. The effects of the introduction of Cs on the crystal structures, the crystallization process, and the band structures have also been investigated, and the hysteresis and stability were improved [43]. The conversion efficiencies were improved by introducing a small amount of Cs to the perovskites, while an excess addition of Cs caused phase separation of the perovskite compounds [44]. In addition, α-HC(NH2)2PbI3 phase was stabilized by introducing Cs to the perovskites [45,46,47,48].
The purpose of the present work is to investigate the effects of a co-addition of GA and Cs to CH3NH3PbI3 perovskite solar cells using first-principles calculations and experiments. A superstructure model was used to calculate the band structures, the partial density of states (DOS), and the electron density distributions. In addition, perovskite solar cells with co-added GA and Cs were fabricated and characterized to compare the experimental results with calculations. The co-addition of GA/Cs to the perovskites is expected to improve the device performance.

2. Calculation and Experimental Methods

The band structures and partial DOS of the perovskite crystal were determined with first-principles calculation. The ab initio quantum calculations were performed using the Vanderbilt ultrasoft pseudo-potentials, scalar relativistic generalized gradient approximations, and the Perdew–Burke–Ernzerhof exchange-correlation function (Quantum Espresso software, V5.2.1). The used parameters were as follows: the crystal system with 2 × 2 × 2 or 3 × 3 × 3 supercells, experimental lattice constants, a kinetic cut-off energy for the wave functions (25 Ry), and charge density (225 Ry) [49,50,51,52]. Although the doped structure was distorted by structural optimization, it is difficult to calculate the band structures from the distorted crystal lattice. Therefore, the framework of the crystal lattice was fixed in the present calculations to estimate the electronic structures.
A fabrication process of photovoltaic devices of the present work is the same as those of the previous work [53]. F-doped tin oxide (FTO, Nippon Sheet Glass Company, Tokyo, Japan, ~10 Ω/□) substrates were cleaned with methanol and acetone in an ultrasonic bath and an ultraviolet ozone cleaner (Asumi Giken, Tokyo, Japan, ASM401N). Next, 0.15 and 0.30 M precursor solutions of TiO2 compact layers were prepared from 1-butanol (Fujifilm Wako Pure Chemical Corporation, Osaka, Japan) and titanium diisopropoxide bis(acetylacetonate) (Sigma-Aldrich, Tokyo, Japan). These precursor solutions of compact TiO2 were spin-coated on the FTO substrate at 3000 rpm for 30 s, and the substrates were annealed at 125 °C for 5 min. To form a uniform compact TiO2 layer, the 0.30 M precursor solution was spin-coated twice. Then, the FTO substrate was annealed at 550 °C for 30 min to form the compact TiO2 layer. After that, a TiO2 paste (precursor solution for mesoporous TiO2) was spin-coated on the compact TiO2 layer at 5000 rpm for 30 s. This TiO2 paste was prepared by mixing distilled water (0.5 mL), poly(ethylene glycol) PEG-20000 (Nacalai Tesque, Kyoto, Japan, PEG #20000, 20 mg), and TiO2 powder (Aerosil, Tokyo, Japan, P-25, 200 mg). This solution was further mixed with the surfactant Triton X-100 (Sigma-Aldrich, 10 μL) and acetylacetone (Wako Pure Chemical Industries, 20 μL) for 30 min, and it was left untouched for 24 h to remove bubbles in the solution. To form the mesoporous TiO2 layer, the TiO2-coated substrates were annealed at 550 °C for 30 min.
The perovskite compounds were prepared with N,N-dimethylformamide (Sigma-Aldrich) by mixing CH3NH3I (Tokyo Chemical Industry, 190.8 mg) and PbCl2 (Sigma-Aldrich, 111.2 mg) at 60 °C for 24 h. This solution was the basic precursor of MAPbI3, prepared with a molar ratio of 3:1. MA1-x-yGAxCsyPbI3 precursors were prepared by adding guanidinium iodide (Sigma-Aldrich) and cesium iodide (CsI, Daiichi Kigenso Kagaku Kogyo Co., Ltd., Osaka, Japan) to control the desired molar ratio. Perovskite precursor solutions were spin-coated on the mesoporous TiO2 layer three times using a hot air blowing method during the spin-coatings. The perovskite solutions were spin-coated at 2000 rpm for 60 s. On the third spin-coating, decaphenylcyclopentasilane (DPPS; SI-30-15, Osaka Gas Chemicals, Osaka, Japan, 10 mg) solution was dropped on the perovskite layer [54]. DPPS is a kind of polysilane used for hole transport and stability [55]. The polysilane solution was prepared by mixing chlorobenzene (Fujifilm Wako Pure Chemical Corporation, 0.5 mL) with DPPS. After the spin-coating, the prepared cells were annealed at 190 °C for 10 min in air to form the perovskite layer.
A hole transport layer was prepared with spin-coating on the perovskite layer. A precursor solution of the hole transport layer was prepared by mixing chlorobenzene (Fujifilm Wako Pure Chemical Corporation, 0.5 mL) and 2,2′,7,7′-tetrakis-(N,N-di(pmethoxyphenyl)amine)-9,9′-spirobifluorene (spiro-OMeTAD; Sigma-Aldrich, 36.1 mg) for 12 h. Lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI, Tokyo Chemical Industry, 260 mg) and tris(2-(1H-pyrazol-1-yl)-4-tertbutylpyridine) cobalt(III)tri[bis(trifluoromethane)sulfonimide] (FK209, Sigma-Aldrich, 188 mg) were each added to acetonitrile (Sigma-Aldrich, 0.5 mL). Immediately before film formation, 4-tertbutylpyridine (Sigma-Aldrich, 18 μL), the prepared solution of Li-TFSI (10 μL), and the solution of FK209 (4 μL) were mixed at 70 °C for 30 min. The spiro-OMeTAD solution was then spin-coated on the perovskite layer at 4000 rpm for 30 s. Finally, a gold (Au) thin film was evaporated onto the hole transport layer as the top metal electrode. The layered structures of the solar cells were denoted FTO/TiO2/perovskite/spiro-OMeTAD/Au.
The J–V characteristics of the photovoltaic cells were measured under illumination at 100 mW cm−2 using an air mass 1.5 solar simulator (San-ei Electric, Osaka, Japan, XES-301S) and dark condition. The J–V measurements were performed using a source measure unit (Keysight, Santa Rosa, CA, USA, B2901A Precision SMU). The scan rate and sampling time were ~0.08 V s−1 and 1 ms, respectively. Three cells were tested for each condition. The solar cells were illuminated through the sides of the FTO substrates, and the illuminated area was 0.080 cm2. The EQE of the cells was also measured (Enli Technology, Kaohsiung, Taiwan, QE-R). The microstructures of the cells were investigated using an X-ray diffractometer (Bruker, Billerica, MA, USA, D2 PHASER) and a scanning electron microscope (SEM, Jeol, Tokyo, Japan, JSM6010PLUS/LA) equipped with energy dispersive X-ray spectrometry.

3. Results and Discussion

3.1. Calculations

To estimate the structural stability of perovskite compounds, a tolerance factor (t) was calculated using the following equation:
t = r A + r X 2 r B + r X
where rA, rB, and rX are the ionic radii of the A, B, and X ions, respectively, for the ABX3 perovskite structures [56]. When the t-value is 1, the perovskite compound has a stable crystal structure with cubic symmetry. From the previous experimental studies on perovskite compounds, the perovskite structure could be formed in the range of 0.813 ≤ t ≤ 1.107 [4]. Calculated t-factors of the perovskite compounds are listed in Table 1. From this calculation, a co-addition of GA and Cs could be one of the effective ways to stabilize the MAPbI3 structure.
Figure 1a is a perspective structure model of MA0.75GA0.125 Cs0.125PbI3. MA molecules are substituted with GA and Cs, which are located diagonally in the 2 × 2 × 2 supercell. Based on this structure model, the physical properties could be estimated. Figure 1b,c are projected structure models along the [100] and [111] directions, respectively. Figure 1d,e are corresponding electron diffraction patterns of MA0.75GA0.125Cs0.125PbI3 calculated along the [100] and [111] directions, respectively. Although the ordinary cubic structure of MAPbI3 [4] shows four-fold and six-fold symmetries from the [100] and [111] incidences, the calculated electron diffraction patterns in Figure 1d,e does not show the perfect four-fold and six-fold symmetries. This indicates that the high symmetry of the space group of Pm 3 _ m for MAPbI3 was reduced to a lower symmetry by doping Cs and GA at the MA sites.
Figure 2 shows the calculated band structures and the partial DOS of the MA0.75GA0.125 Cs0.125PbI3 perovskite. The calculated energy gaps, the effective mass ratios of carriers, and the total energies of the crystals are listed in Table 2. Since the partial substitution of MA with GA and Cs is expected to increase the energy gap, the open circuit voltage of the device would be improved. Since the effective mass ratios of carriers increase with the GA/Cs introduction, the short-circuit current density may decrease. On the other hand, the total energy decreases with the GA/Cs introduction, so the device stability could be improved. From the calculated partial DOS, the iodine p and lead p orbitals are dominant in the valence band and the conduction band, respectively, and a charge transfer is expected between these orbitals. Since the orbital-derived energy levels of the Cs, carbon, and nitrogen in GA are located apart from the energy gap, the GA/Cs addition might have little effect on the charge transfer.
Guided with the first-principle calculations and experimental evaluations, an addition of a small amount of GA to the MAPbI3 was effective to stabilize the perovskite structure [17,18]. Although the GA addition expands and distorts the crystal lattice of MAPbI3, Cs reduces the distortion of the lattice, which could lead to the stability of the perovskite crystal.
The calculated electron density distribution is shown in Figure 3. The electron densities are high around Pb, MA, and GA. Meanwhile, the electron density is low around Cs, which also predicts that Cs would not contribute to the charge transfer.

3.2. Experimental Results

Figure 4 shows the current density–voltage (J–V) characteristics of the fabricated perovskite solar cells. Table 3 shows the cell parameters of perovskite solar cells doped with Cs and GA. The conversion efficiencies of the device were improved by substituting MA with 12.5% GA in the MAPbI3, and the conversion efficiencies were further improved by adding 12.5% GA and 3% Cs at the MA site simultaneously. The device performance was significantly reduced with an excess addition of GA or Cs.
The calculated data on the MA0.75GA0.125Cs0.125PbI3 predicted a decrease of JSC, which agrees with the experimental data on the GA 12.5% + Cs 9% device. An addition of a small amount of Cs (3%) improved the JSC, which would be due to a mitigation of the lattice distortion by the Cs. On the other hand, a decrease of the measured VOC in Table 3 might be due to a decrease of the conduction band minimum, as calculated in Table 2.
Figure 5 shows a scanning electron microscope image and the elemental mapping images of the GA 12.5% + Cs 3% device. The shape of the perovskite grains is granular, and the grains are uniformly distributed. Pb, I, and Cs are distributed at the same regions, which indicates the perovskite compounds consist of these elements.
Figure 6 shows X-ray diffraction patterns of the fabricated perovskite solar cells. Table 4 shows the parameters obtained from the X-ray diffraction measurements. The lattice constants decrease with an increasing Cs addition, indicating that the MA at the A-site cation is substituted with Cs with a smaller ionic radius. Increasing the amount of GA from 12.5% to 25.0% increases the lattice constants of perovskites, which is due to the substitution of MA with GA with a larger ionic radius. As Cs content is increased from 3% to 6% under the addition of GA 25%, the lattice constant increases, which would be due to an occupation of Cs at the interstitial sites caused by a lattice distortion around the GA. An increase in the crystallite sizes by increasing Cs from 0% to 9% or GA from 12.5% to 25.0% suggests that the introduction of suitable amounts of Cs or GA may contribute to the grain growth. For the GA 12.5% + Cs 6~9% device, PbI2 peaks are observed, which might be due to a decomposition of the perovskites from the increasing Cs contents (6~9%) close to the GA content (12.5%).
Projected and perspective structure models of MA0.815GA0.148Cs0.037PbI3 are shown in Figure 7a,b, respectively. To investigate the effects of introducing a small amount of Cs, the structure model with a 3 × 3 × 3 supercell was constructed. A calculated X-ray diffraction pattern of the MA0.815GA0.148Cs0.037PbI3 is shown in Figure 6c, which indicates changes in the diffraction intensities compared with those of the MAPbI3.
Changes of conversion efficiencies of the present devices are listed in Table 5. The decrease rate of the conversion efficiency for GA 12.5% + Cs3% is smaller than that for GA 12.5%, which is due to the stabilization effect of Cs as an inorganic cation. Although degradation of the device performance is due to a desorption of MA from the MAPbI3, the MA desorption could be suppressed with the Cs incorporation with the perovskite crystal, which leads to an improvement of the device durability. The decrease rates of conversion efficiencies increased by adding excess amounts of Cs or GA, which might be caused by a decomposition of the perovskite crystals under the presence of excess multiple cations with different ionic radii.
For the fabricated device with a MA0.845GA0.125Cs0.03PbI3 perovskite compound, the high photoconversion efficiency and stability were obtained, which agree with the calculated results. Although several works on GAPbI3 [57] and CsPbI3 [58,59] compounds have been reported, few works have been reported on the co-addition of GA and Cs to MAPbI3. The present work indicated the effectiveness of the co-addition of GA and Cs to the MAPbI3 on the photovoltaic properties.

4. Conclusions

The effects of a simultaneous addition of GA and Cs to MAPbI3 perovskite solar cells were investigated with first-principles calculations and experiments. Although the calculations predicted that a substitution of MA with GA and Cs would decrease the carrier mobility, the conversion efficiency of the actual devices increased from 10.3% to 12.27% with the co-addition of GA/Cs. An excess addition of Cs or GAs decreases the device properties, which would be due to the lattice distortion and the reduction of the carrier mobility. The changes of the lattice constants indicated that the Cs and GA are incorporated into the A-site of the perovskite. The crystallite sizes and the (100) crystal orientations also suggest that the GA/Cs addition affects the process of the grain growth. The stability evaluation of the devices showed that the device with GA 12.5% + Cs 3% exhibited the highest conversion efficiency and stability. A modification of the A-site cation affects the initial efficiencies and durability of the devices, and the device performance can be improved further by combining stable organic cations with alkali metals.

Author Contributions

Conceptualization, T.O. and S.U.; methodology, T.O., S.U., and A.S.; formal analysis, T.O., S.U., R.O., A.S., and I.O.; investigation, T.O., S.U., and A.S.; resources, S.F., T.T., and T.H.; data curation, T.O. and S.U.; writing—original draft preparation, T.O., S.U., and R.O.; writing—review and editing, T.O., S.U., R.O., A.S., I.O., S.F., T.T., and T.H.; project administration, T.O.; funding acquisition, T.O. All authors have read and agreed to the published version of the manuscript.

Funding

This research was partly funded by the Japan Society for the promotion of Science as a Grant-in-Aid for Scientific Research (C) 21K04809.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Acknowledgments

The authors would like to acknowledge Takahiro Kamo, Daiichi Kigenso Kagaku Kogyo Co., Ltd., for providing CsI.

Conflicts of Interest

The authors declare no conflict of interest.

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Inorganics 11 00273 g001 550
Figure 1. Structure models of (a) perspective view, (b) [100], and (c) [111] incidence of MA0.75GA0.125 Cs0.125PbI3. Calculated electron diffraction patterns along (d) [100] and (e) [111] directions.
Figure 1. Structure models of (a) perspective view, (b) [100], and (c) [111] incidence of MA0.75GA0.125 Cs0.125PbI3. Calculated electron diffraction patterns along (d) [100] and (e) [111] directions.
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Inorganics 11 00273 g002 550
Figure 2. (a) Band structure and (b) partial density of states of MA0.75GA0.125Cs0.125PbI3.
Figure 2. (a) Band structure and (b) partial density of states of MA0.75GA0.125Cs0.125PbI3.
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Inorganics 11 00273 g003 550
Figure 3. Calculated electron density distribution of MA0.75GA0.125Cs0.125PbI3.
Figure 3. Calculated electron density distribution of MA0.75GA0.125Cs0.125PbI3.
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Inorganics 11 00273 g004 550
Figure 4. J−V characteristics of the present perovskite solar cells.
Figure 4. J−V characteristics of the present perovskite solar cells.
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Inorganics 11 00273 g005 550
Figure 5. SEM image and elemental mapping images (Pb, I, C, N, and Cs) of the device with GA 12.5% + Cs 3%.
Figure 5. SEM image and elemental mapping images (Pb, I, C, N, and Cs) of the device with GA 12.5% + Cs 3%.
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Inorganics 11 00273 g006 550
Figure 6. Measured X-ray diffraction patterns of the present perovskite solar cells.
Figure 6. Measured X-ray diffraction patterns of the present perovskite solar cells.
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Inorganics 11 00273 g007 550
Figure 7. (a) Projected and (b) perspective structure models and (c) calculated X-ray diffraction pattern of MA0.815GA0.148Cs0.037PbI3.
Figure 7. (a) Projected and (b) perspective structure models and (c) calculated X-ray diffraction pattern of MA0.815GA0.148Cs0.037PbI3.
Inorganics 11 00273 g007
Table
Table 1. Calculated t-factors of perovskite compounds.
Table 1. Calculated t-factors of perovskite compounds.
Perovskitet
MAPbI30.912
GAPbI31.039
CsPbI30.851
MA0.75GA0.125Cs0.125PbI30.920
MA0.845GA0.125Cs0.03PbI30.926
Table
Table 2. Calculated parameters for the perovskite crystals. VBM: valence band maximum. CBM: conduction band minimum.
Table 2. Calculated parameters for the perovskite crystals. VBM: valence band maximum. CBM: conduction band minimum.
PerovskiteVBM
(eV)		CBM
(eV)		Eg
(eV)		me*/m0mh*/m0Ecell
(eV cell−1)
MAPbI30.7862.141.340.350.20−3497
MA0.75GA0.125Cs0.125PbI30.2691.661.390.480.33−3500
Table
Table 3. Photovoltaic parameters of present perovskite photovoltaic devices. JSC: short-circuit current density. VOC: open-circuit voltage. FF: fill factor. RS: series resistance. RSh: shunt resistance. η: conversion efficiency. ηave: averaged efficiency of three cells.
Table 3. Photovoltaic parameters of present perovskite photovoltaic devices. JSC: short-circuit current density. VOC: open-circuit voltage. FF: fill factor. RS: series resistance. RSh: shunt resistance. η: conversion efficiency. ηave: averaged efficiency of three cells.
DevicesJSC
(mA cm−2)		VOC
(V)		FFRS
(Ω cm2)		RSh
(Ω cm2)		η
(%)		ηave
(%)		Eg
(eV)
GA 0% + Cs 0%19.70.8900.5897.2054,80010.35.831.56
GA 12.5% + Cs 0%22.40.8240.6323.4476211.658.151.60
GA 12.5% + Cs 3%21.80.8510.6633.89154012.2710.181.55
GA 12.5% + Cs 6%14.60.7640.6212.456956.924.981.55
GA 12.5% + Cs 9%12.10.7050.6202.055575.413.891.59
GA 25% + Cs 3%18.30.8740.6862.7149010.963.701.56
GA 25% + Cs 6%16.60.8100.5724.775027.706.841.55
Table
Table 4. Structural parameters of perovskite crystals with added Cs and GA.
Table 4. Structural parameters of perovskite crystals with added Cs and GA.
DevicesLattice constant
(Å)		Crystallite size (Å)I100 / I210
GA 0% + Cs 0%6.270(0)4826.77
GA 12.5% + Cs 0%6.273(0)3652.25
GA 12.5% + Cs 3%6.268(0)44719.25
GA 12.5% + Cs 6%6.265(0)4695.97
GA 12.5% + Cs 9%6.263(6)3922.96
GA 25% + Cs 3%6.288(1)4756.83
GA 25% + Cs 6%6.297(0)4516.50
Table
Table 5. Changes of conversion efficiencies for the present perovskite solar cells.
Table 5. Changes of conversion efficiencies for the present perovskite solar cells.
DevicesTime
(Day)		ηave
(%)		Change of η
(%)		Decrease Rate
(% Day−1)
GA 12.5% + Cs 0%2245.8671.90.13
GA 12.5% + Cs 3%2529.0288.60.04
GA 12.5% + Cs 6%1841.9238.60.34
GA 12.5% + Cs 9%1841.4437.00.34
GA 25% + Cs 3%1043.0081.10.18
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Oku, T.; Uchiya, S.; Okumura, R.; Suzuki, A.; Ono, I.; Fukunishi, S.; Tachikawa, T.; Hasegawa, T. Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells. Inorganics 2023, 11, 273. https://doi.org/10.3390/inorganics11070273

AMA Style

Oku T, Uchiya S, Okumura R, Suzuki A, Ono I, Fukunishi S, Tachikawa T, Hasegawa T. Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells. Inorganics. 2023; 11(7):273. https://doi.org/10.3390/inorganics11070273

Chicago/Turabian Style

Oku, Takeo, Shoma Uchiya, Riku Okumura, Atsushi Suzuki, Iori Ono, Sakiko Fukunishi, Tomoharu Tachikawa, and Tomoya Hasegawa. 2023. "Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells" Inorganics 11, no. 7: 273. https://doi.org/10.3390/inorganics11070273

APA Style

Oku, T., Uchiya, S., Okumura, R., Suzuki, A., Ono, I., Fukunishi, S., Tachikawa, T., & Hasegawa, T. (2023). Effects of Co-Addition of Guanidinium and Cesium to CH3NH3PbI3 Perovskite Solar Cells. Inorganics, 11(7), 273. https://doi.org/10.3390/inorganics11070273

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