Improving Microstructure and Photoelectric Performance of the Perovskite Material via Mixed Solvents

doi:10.15541/jim20160584

Abstract

Abstract:

The perovskite (CH₃NH₃PbI₃) thin films were prepared with pure N, N-dimethyl formamide (DMF), pure dimethyl sulfoxide (DMSO) and their mixtures with different volume ratios. The impact of different solvents on the microstructure and photoelectric properties of perovskite materials was systematically investigated. Results show that with the increase of DMSO in mixed solvents, the average grain size of CH₃NH₃PbI₃ increases while the residual lead iodide (PbI₂) decreases. Moreover, the ratio of ordered CH₃NH₃PbI₃crystals increases firstly and then decreases, and the highest ratio is achieved when the volume ratio of DMSO in mixed solvent is 60%. In addition, the relationship among Urbach energy characterization, time-resolved photoluminescence characterization and unreacted PbI₂ residue indicates that the trace amounts of PbI₂ may effectively passivate the defects in perovskite thin films, so as to prolong the carrier lifetime. The inverted planar heterojunction perovskite thin film solar cells were fabricated. The highest power conversion efficiency (PCE) of 15.1% (V_OC=0.99 V; J_SC=20.9 mA/cm²; FF=0.73) is achieved when the volume ratio of DMSO in mixed solvent is 30%. These results reveal that mixed solvents with appropriate volume ratio is favorable for the improvement of microstructure and photoelectric properties of perovskite materials.

Key words: mixed solvents, perovskite, photoelectric properties, passivation

CLC Number:

O472

GUO Xiu-Bin, YU Wei, Li Jing, JIANG Zhao-Yi, MA Deng-Hao, LIU Hai-Xu. Improving Microstructure and Photoelectric Performance of the Perovskite Material via Mixed Solvents[J]. Journal of Inorganic Materials, 2017, 32(8): 870-876.

Figures/Tables 11

Fig. 1 Surface morphologies of perovskite films prepared by different solvents(a) Pure DMF solvent; (f) Pure DMSO solvent; (b) 15% DMSO; (c) 30% DMSO; (d) 60% DMSO; (e) 80% DMSO

Fig. 2 XRD patterns of perovskite thin films prepared by mixed solvents with different volume ratios

Fig. 3 UV-Vis absorption spectra of perovskite films prepared by mixed solvents with different volume ratios

Fig. 4 Cross-section views of perovskite films prepared by different solvents(a) Pure DMF solvent; (d) Pure DMSO solvent; (b) 30% DMSO; (c) 60% DMSO

Fig. 5 Steady-state photoluminescence spectra of perovskite films prepared by mixed solvents with different volume ratios

Fig. 6 Fit of PL spectrum for perovskite film based on pure DMF solvent (a); the change trend of the ratio of ordered to disordered phases with the increase of DMSO (b)

Fig. 7 TRPL of perovskite films prepared by mixed solvents with different volume ratios

Table 1 Carrier lifetime extracted from TR-PL decay curves

Sample	τ₁/ns	τ₂/ns
DMF	2.0	81
15%	3.1	85
30%	2.6	94
60%	3.5	90
80%	1.8	77
DMSO	1.7	67

Fig. 8 (a) Device structure of inverted planar heterojunction perovskite solar cells and (b) the cross-section view of device

Fig. 9 J-V characteristic curves of devices prepared by mixed solvents with different volume ratios

Table 2 Photovoltaic parameters of devices prepared by mixed solvents with different volume ratios

Devices	J_SC/(mA·cm^-2)	V_OC/V	FF/%	PCE/%
DMF	15.4	0.91	66.3	9.3
15%	18.9	0.95	70.3	12.6
30%	20.9	0.99	72.8	15.1
60%	20.2	0.96	71.9	13.9
80%	17.2	0.94	69.2	11.2
DMSO	14.7	0.91	63.1	8.4

References 26

[1]	KOJIMA A, TESHIMA K, SHIRAI Y, et al.Organometal halide perovskites as visible-light sensitizers for photovoltaic cells.Journal of the American Chemical Society, 2009, 131(17): 6050-6051.
[2]	ETGAR L, GAO P, XUE Z, et al.Mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells.Journal of the American Chemical Society, 2012, 134(42): 17396-17399.
[3]	LEE M M, TEUSCHER J, MIYASAKA T, et al.Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites.Science, 2012, 338(6107): 643-647.
[4]	PARK N G.Organometal perovskite light absorbers toward a 20% efficiency low-cost solid-state mesoscopic solar cell.Journal of Physical Chemistry Letters, 2013, 4(15): 2423-2429.
[5]	NOH J H, SANG H I, JIN H H, et al.Chemical management for colorful, efficient, and stable inorganic-organic hybrid nanostructured solar cells.Nano Letters, 2013, 13(4): 1764-1769.
[6]	JEON N J, NOH J H, YANG W S, et al.Compositional engineering of perovskite materials for high-performance solar cells.Nature, 2015, 517(7535): 476-480.
[7]	MATTEOCCI F, RAZZA S, DI G F, et al.Solid-state solar modules based on mesoscopic organometal halide perovskite: a route towards the up-scaling process.Physical Chemistry Chemical Physics, 2014, 16(9): 3918-3923.
[8]	JENG J Y, CHIANG Y F, LEE M H, et al.CH3NH3PbI3 perovskite/fullerene planar-heterojunction hybrid solar cells.Advanced Materials, 2013, 25(27): 3727-3732.
[9]	IM J H, JANG I H, PELLET N, et al.Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells.Nature Nanotechnology, 2014, 9(11): 927-932.
[10]	ZHAO Y, ZHU K.Solution chemistry engineering toward high-efficiency perovskite solar cells.Journal of Physical Chemistry Letters, 2014, 5(23): 4175-4186.
[11]	WU Y, ISLAM A, YANG X, et al.Retarding the crystallization of PbI2 for highly reproducible planar-structured perovskite solar cells via sequential deposition.Energy & Environmental Science, 2014, 7(9): 2934-2938.
[12]	WAKAMIYA A, ENDO M, SASAMORI T, et al.Reproducible fabrication of efficient perovskite-based solar cells: X-ray crystallographic studies on the formation of CH3NH3PbI3 Layer.Chemistry Letters, 2014, 43(5): 711-713.
[13]	TANG Z, TANAKA S, ITO S, et al.Investigating relation of photovoltaic factors with properties of perovskite films based on various solvents.Nano Energy, 2016, 21: 51-61.
[14]	JEON N J, NOH J H, KIM Y C, et al.Solvent engineering for high-performance inorganic-organic hybrid perovskite solar cells.Nature Materials, 2014, 13(9): 897-903.
[15]	LI W, FAN J, LI J, et al.Controllable grain morphology of perovskite absorber film by molecular self-assembly toward efficient solar cell exceeding 17%.Journal of the American Chemical Society, 2015, 137(32): 10399-10405.
[16]	CAI B, ZHANG W H, QIU J, et al.Solvent engineering of spin-coating solutions for planar-structured high-efficiency perovskite solar cells.Chinese Journal of Catalysis, 2015, 36(8): 1183-1190.
[17]	YANG W S, NOH J H, JEON N J, et al.High-performance photovoltaic perovskite layers fabricated through intramolecular exchange.Science, 2015, 348(6240): 1234-1237.
[18]	CHEN Q, ZHOU H, HONG Z, et al.Planar heterojunction perovskite solar cells via vapor-assisted solution process.Journal of the American Chemical Society, 2014, 136(2): 622-625.
[19]	ZHAO L, LUO D, WU J, et al.High-performance inverted planar heterojunction perovskite solar cells based on lead acetate precursor with efficiency exceeding 18%.Advanced Functional Materials, 2016, 26(20): 3508-3514.
[20]	IKHMAYIES S J, AHMAD-BITAR R N. An investigation of the bandgap and Urbach tail of vacuum-evaporated SnO2 thin films.Physica Scripta, 2011, 84(5): 143-146.
[21]	WASSNER T A, LAUMER B, MAIER S, et al. Optical properties and structural characteristics of ZnMgO grown by plasma assisted molecular beam epitaxy. Journal of Applied Physics, 2009, 105(2): 023505-1-6.
[22]	LIU F, DONG Q, WONG M K, et al. Is excess PbI2 beneficial for perovskite solar cell performance. Advanced Energy Materials, 2016, 6(7): 1502206-1-9.
[23]	PARK B W, JAIN S M, ZHANG X, et al.Resonance Raman and excitation energy dependent charge transfer mechanism in halide- substituted hybrid perovskite solar cells.ACS Nano, 2015, 9(2): 2088-2101.
[24]	PELLET N, GAO P, GREGORI G, et al.Mixed-organic-cation perovskite photovoltaics for enhanced solar-light harvesting.Angewandte Chemie, 2014, 53(12): 3151-3157.
[25]	CHEN Q, ZHOU H, SONG T B, et al.Controllable self-induced passivation of hybrid lead iodide perovskites toward high performance solar cells.Nano Letters, 2014, 14(7): 4158-4163.
[26]	XING G, MATHEWS N, SUN S, et al.Long-range balanced electron-and hole-transport lengths in organic-inorganic CH3NH3PbI3.Science, 2013, 342(6156): 344-347.