利用混合溶剂实现钙钛矿材料微观结构和光电性能优化

doi:10.15541/jim20160584

摘要/Abstract

摘要：

采用纯N, N-二甲基甲酰胺(DMF)溶剂、纯二甲基亚砜(DMSO)溶剂以及DMSO/DMF不同体积比例混合溶剂制备钙钛矿(CH₃NH₃PbI₃)薄膜, 并系统研究了不同溶剂对钙钛矿薄膜微结构及光电特性的影响。结果表明, 随着DMSO在混合溶剂中比例增加, 钙钛矿薄膜平均晶粒尺寸增大, 碘化铅(PbI₂)残留量降低, 同时薄膜中有序的钙钛矿晶体所占比例呈现先增大后减小的趋势, 并且当DMSO占混合溶剂体积比为60%时达到最大。薄膜Urbach能, 载流子寿命以及PbI₂含量之间的关系表明, 微量的PbI₂可有效钝化钙钛矿薄膜的缺陷。经过优化后(DMSO占混合溶剂体积比为30%), 钙钛矿太阳电池的光电转换效率达到15.1 % (V_OC=0.99 V; J_SC=20.9 mA/cm²; FF=0.73)。

关键词: 混合溶剂, 钙钛矿, 光电特性, 钝化

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

中图分类号:

O472

郭秀斌, 于威, 李婧, 蒋昭毅, 马登浩, 刘海旭. 利用混合溶剂实现钙钛矿材料微观结构和光电性能优化[J]. 无机材料学报, 2017, 32(8): 870-876.

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.

图/表 11

图1 不同溶剂制备的钙钛矿薄膜表面形貌

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

图2 不同溶剂制备的钙钛矿薄膜的XRD图谱

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

图3 不同溶剂制备的钙钛矿薄膜的吸收谱

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

图4 不同溶剂制备的钙钛矿薄膜截面图

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

图5 不同溶剂制备的钙钛矿薄膜的光致发光谱

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

图6 纯DMF溶剂制备的钙钛矿薄膜PL拟合结果(a)以及有序相和无序相比值随DMSO含量变化趋势图(b)

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)

图7 不同溶剂制备的钙钛矿薄膜时间分辨的光致发光谱

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

表1 时间分辨的光致发光双指数衰减拟合参数

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

图8 器件结构示意图(a)以及截面图(b)

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

图9 不同溶剂制备的钙钛矿电池的J-V特性曲线

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

表2 不同溶剂制备的钙钛矿电池的光伏参数

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

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