MS  >> Vol. 10 No. 1 (January 2020)

    溶剂退火制备高质量MA3Bi2I9钙钛矿薄膜与太阳能电池
    Solvent Annealing for High Quality MA3Bi2I9 Perovskite Thin Films and Solar Cells

  • 全文下载: PDF(1107KB) HTML   XML   PP.31-39   DOI: 10.12677/MS.2020.101005  
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作者:  

艳领,王星辰,孙振兴,K. P. Homewood,高 云,雷丙龙:湖北大学材料与工程学院,湖北 武汉

关键词:
无铅钙钛矿蒸镀法气氛处理太阳能电池Lead Free Perovskite Evaporation Atmosphere Treatment Solar Cell

摘要:

与铅钙钛矿太阳能电池相比,铋基钙钛矿太阳能电池在无毒性和稳定性方面表现出很好的优势。在(CH3NH3)3Bi2I9钙钛矿太阳能电池的研究中,光吸收层薄膜的质量严重制约着电池的光电转化效率。本研究在两步蒸镀与掺氯的基础上,采用DMF气氛退火处理,获得了高致密、无孔洞且大晶粒的(CH3NH3)3Bi2I9薄膜。该处理减少了薄膜内部缺陷,增强薄膜光吸收,增加载流子寿命。与未处理的薄膜相比,电池的光电转换效率提升了52.9%。本研究为钙钛矿薄膜质量的优化以及器件性能的提升提供了可行的解决方案。

Bismuth based perovskite solar cells possess the features of non-toxicity and high stability, which are considered as two significant factors in the emerging perovskite solar cells. The quality of the light absorption layer has a remarkable impact on the conversion efficiency of (CH3NH3)3Bi2I9 per-ovskite solar cells. Herein, (CH3NH3)3Bi2I9 thin films with features of highly compact, pinhole-free and large grains were prepared by procedures of two-step evaporation, chlorine doping and an-nealing under a DMF atmosphere. The DMF solvent annealing can diminish the internal defects of thin-film, and thereby enhances the absorbance as well as prolonging the life time of charge carries. The conversion efficiency shows dramatic enhancement by 52.9% compared with the solar cells from thin-films without DMF annealing. This work provides insights into the (CH3NH3)3Bi2I9 per-ovskite solar cells with optimized thin-film quality and improved device performance.

1. 引言

在过去的十年里,人们在有机无机杂化钙钛矿太阳能电池方面取得了显著成果。钙钛矿太阳能电池的光电转换效率从不足4.0%飙升到了25.2% [1] [2] [3] [4],已经接近传统的硅太阳能电池,发展速度远远超过了其他无机或有机太阳能电池。目前大多数钙钛矿材料都是基于铅基杂化钙钛矿,以重金属铅为核心元素。众所周知,铅是一种环境非友好型元素。此外,铅基钙钛矿材料的不稳定性仍然是电池发展途中的一个巨大的挑战,这可能会限制其大规模的工业应用和发展 [5]。为了解决这个问题,无铅钙钛矿随之引起了人们的关注 [6] [7] [8]。首先进入研究视野的是与铅同主族具有相同结构的锡元素,锡基钙钛矿太阳能电池效率已经达到8.12% [9]。但是,当锡基电池暴露在空气中时,Sn2+被急剧氧化成Sn4+,使电子载体产生较大的变化,使电池效率急剧下降 [10]。其次是基于铋基材料的电池。因为Bi3+的电子排布和Pb2+一样,均是6s26p0,离子半径差距小,电负性接近,形成钙钛矿结构不易变形,而且铋基钙钛矿与铅基钙钛矿在带隙可调与可溶液加工等方面也有相似性,所以成为有明显优势的铅基替代材料 [11]。

近年来,铋基钙钛矿材料A3Bi2X9 (A = Cs+,Ag+ CH 3 NH 3 + (MA);X = Cl,Br,I) [12] 已经被大量研究,并用于太阳能电池的制备。在这些研究中,无毒(CH3NH3)3Bi2I9 (MBI)太阳能电池获得了快速发展。与铅基钙钛矿太阳能电池相比,MBI电池展现出优异的稳定性——即使在空气中储存21天后,电池的性能也只有较小下降 [13]。但是MBI电池光电转换效率一直无法提升,现阶段的光电转换效率(PCE)约为0.2%~3.17% [14] [15]。器件性能较差的主要原因在于MBI具有1.90~2.20 eV较宽的带隙和较差的光吸收层薄膜质量。在目前的研究中,MBI薄膜的制备方法主要借鉴于铅基钙钛矿的制备方法,主要有一步溶液旋涂法 [16],两步蒸镀或旋涂法 [17],反溶剂旋涂法等 [18] [19]。采用这些方法制备的MBI薄膜有六棱柱晶体、孤立六边形、不致密薄膜等多种非连续形态,这些通常认为不适合光能的高效吸收和转换。

为了制备高致密无针孔铋基钙钛矿薄膜,广大科研人员系统研究了成膜工艺和器件的建构。Zhang等人通过控制电子传输层的加工和MBI层的结构调控 [20],一步旋涂法制备了PCE为0.42%的MA3Bi2I9太阳能电池;Gao组报道了一种两步蒸镀法,高真空蒸镀BiI3和低真空蒸镀MAI,使BiI3向MBI均匀转化,制备的太阳能电池实现了1.64%的光电转换效率 [21] ;随后,Li等人在两步蒸镀过程中引入氯元素,有效抑制了MBI薄膜在c轴的优先生长,制备出了平整且晶粒尺寸较大的MBI薄膜 [22]。

在前期的探索中表明,高质量MBI薄膜是制备高性能器件的关键。本研究对MBI薄膜的制备进行了进一步的优化:采用两步蒸镀法,并在退火过程中使用DMF气氛处理,使晶粒进一步长大,制备出了平整致密且具有良好重复性的MBI薄膜,并制备成完整电池。溶剂气氛处理后,电池的开路电压、短路电流、光电转换效率等相对于未处理的电池,均有显著提升。

2. 实验部分

2.1. 所用试剂与药品

本研究所用试剂与规格见表1,所有试剂均无二次提纯。整个实验过程在千级超净间进行,温度控制在23℃~24℃,湿度控制在30%。

Table 1. Reagents and their specifications involved in the work.

表1. 实验药品及规格

2.2. 电池的制备

电池完整制备流程如图1所示,详细制备过程如下:

(1) 用去离子水、玻璃清洗剂、丙酮和酒精顺序超声清洗FTO (辽宁营口优选光电科技有限公司)玻璃。因TiO2具有半导体的性能,导带能级低于有机无机杂化钙钛矿材料,能够分离出空穴–电子对中的电子,故使用致密TiO2薄膜作为电子传输层。将二异丙氧基双乙酰丙酮钛(TiAcAc)溶解于乙醇中,然后以3000 rmp/30 s旋涂在清洗后的FTO上,将基板在500℃保温30分钟,自然冷却到室温,获得厚度为40 nm左右的TiO2致密层。

(2) 将TiO2基板放入紫外箱中紫外处理20分钟,用胶带将基板粘在掩模板上,放入高真空蒸发镀膜机中,在10−4 Pa的真空下蒸镀250 nm的BiI3薄膜,然后将BiI3薄膜放入陶瓷容器中,底部放入1:1 (摩尔比)的MAI和MACl粉末。用铝箔将容器密封,放入真空烘箱,在100 Pa的真空下、180℃加热两个小时,使BiI3完全转变为MBI。结束后自然降温,然后将MBI薄膜取出并在异丙醇中涮洗,以除去表面残留的MAI和MACl;在烘箱中150℃退火处理20 min,退火过程中分别用0 μL,30 μL,60 μL,90 μL和120 μL的DMF溶剂气氛处理。

(3) 空穴传输层溶液通过以下方法配制。使用电子分析天平量取100 mg的Spiro-OMeTAD,然后使用50 μL的移液枪取32 μL TBP (4-叔丁基吡啶)溶液,再取19 μL锂盐(双三氟甲烷磺酰亚胺锂)。其中锂盐溶液通过将520 mg锂盐溶解于1 ml乙腈中获得。最后,将上述三种材料溶解在1 ml氯苯溶液中,轻轻晃动10分钟,使溶液充分混合,即获得空穴传输层旋涂溶液。以3000 rmp/30 s旋涂在铋基钙钛矿薄膜上。最终蒸镀120 nm的金电极制备成完整电池。

Figure 1. Flowchart of preparation of complete solar cell devices

图1. 完整器件制备流程

2.3. 测试与表征

使用场发射扫描电镜(FE-SEM,蔡司,德国)和原子力显微镜(AFM,NT-MDT,Solver Nano,俄罗斯)观察MBI薄膜的形貌;XRD分析是使用X-射线衍射仪(XRD,布鲁克,德国)仪器;紫外可见吸收光谱使用紫外可见近红外光谱仪(UV-3600,岛津,日本)测试;时间分辨荧光光谱使用瞬态光谱设备(TRPL,FluoTime 300,德国)测试,J-V曲线是在标准AM1.5 G (100 mW∙cm2)条件下,使用美国Keithley 2400数字源仪表记录测量。活性层的面积是0.24 cm2

3. 实验结果和分析

Li等人前期的报道中提示 [22],通过Cl元素的掺杂能够制备出大晶粒组成的平整薄膜。但制备的薄膜不是很致密,晶粒与晶粒之间往往会有裂缝存在,这会导致载流子在晶界之间复合,不利于高效太阳能电池的制备。因此我们采用DMF溶剂气氛退火处理来进一步改善薄膜的质量,提升器件性能。图2为不同用量DMF退火处理的MBI薄膜形貌图,从(a)到(e) DMF用量依次为0,30,60,90,120 μL。从图2(a)可以看出,当DMF用量为0 μL,即未用DMF退火时,薄膜的晶粒与晶粒之间有裂缝不致密;从图2(b)、(c)可以看出,当用DMF处理时裂缝逐渐消失,薄膜变得致密平整。这是因为在DMF溶剂退火过程中,某一晶粒的边界数大于相邻各晶粒的边界数时,这些晶界的曲率增大,晶界迁移的推动力相应增大,该晶粒的长大要比周围小晶粒快,因此小晶粒被吞没而大晶粒迅速长大,从而使裂缝消除。图2(c)、(d)为90 μL和120 μL DMF处理的样品,可以看出,虽然晶粒尺寸继续长大,但是薄膜开始出现孔洞(图2(d)中红色圆圈部分),孔洞尺寸和数量随着DMF用量的增加逐渐增多,这可能是因为过量的DMF将部分薄膜溶解导致孔洞的出现。据此,我们将DMF的用量确定为60 μL,用以获得最致密平整的MBI薄膜。图2(f)为60 μL DMF条件处理后的MBI薄膜的AFM图,薄膜的粗糙度为14 nm。

图3是不同用量的DMF处理MBI薄膜的XRD图谱。从图中可以看出:用DMF处理后,薄膜在(002)晶面的峰消失,(101)晶面的峰增强。有文献报道,铋基薄膜会优先在(002)、(004)、(006)晶面优先生长,导致薄膜形成六棱柱或六边形片子。本研究表明,DMF溶剂退火处理能够使薄膜在(101)晶面结晶性增强,抑制c轴的优先结晶。从XRD图谱中能观察到DMF的用量从0增至120 μL时,薄膜的结晶强度先增强后减弱,当使用60 μL处理时薄膜的结晶性最好。这也与薄膜的SEM形貌图保持很好的一致性。

Figure 2. SEM images of MBI films treated with different amounts of DMF. (a) 0 μL; (b) 30 μL; (c) 60 μL; (d) 90 μL; (e) 120 μL; (f) AFM of MBI films treated with 60 μL DMF

图2. 不同用量的DMF溶剂气氛退火处理的MBI薄膜的SEM图。(a) 未处理;(b) 30 μL;(c) 60 μL;(d) 90 μL;(e) 120 μL;(f) 60 μL处理薄膜的AFM图

Figure 3. XRD patterns of MBI films treated with different amounts of DFM

图3. 不同用量DMF处理的MBI薄膜的XRD图谱

MBI薄膜的紫外-可见吸收光谱显示于图4(a)。从图可以看出,DMF处理可以增强光的吸收。通过Tauc plot (图4(c)),获得薄膜的光学带隙为2.18 eV左右,和文献报道的数据相一致 [23]。同时,时间分辨荧光光谱显示于图4(b)。不同DMF用量处理的薄膜载流子寿命有显著的变化:未用DMF处理时,MBI薄膜的载流子寿命为0.45 ns;30 μL DMF处理时,载流子寿命为0.53 ns;60 μL处理时,载流子寿命最长为0.66 ns。随着DMF用量继续增加,载流子的寿命开始减少。载流子寿命越长,扩散距离越远,越有利于电子空穴对的分离,减少激子在电池内部复合,从而提高电池的性能。载流子寿命长也表明薄膜内部缺陷少,因此证明合适用量的DMF处理,可以减少薄膜内部的缺陷。

(a) (b) (c)

Figure 4. (a) UV-Vis absorption spectra of MBI films after treatments with different DMF amounts; (b) Time-resolved fluorescence spectroscopy; (c) Tauc plots of MBI films after treatments with 0 and 60 μL DMF

图4. (a) 不同用量DMF处理后的紫外可见吸收光谱;(b) 时间分辨荧光光谱;(c) 0和60 μL DMF处理后薄膜Tauc图

图5为不同DMF的用量处理下的完整器件在光照下的电流–电压特性曲线。表2给出了电池性能的详细参数。用DMF处理以后,电池的开路电压、短路电流、光电转换效率均有所提升,趋势为随着DMF用量增加,电池性能先变好再变差——这与上述表征的SEM形貌变化,以及载流子寿命先增加后减少等表征相一致。所有结果表明,在本研究的条件下,DMF的用量为60 μL时能够获得高质量的MBI薄膜。在60 μL处理的条件下制备的完整电池开路电压为0.67 V,短路电流为1.02 mA∙cm−2,光电转换效率为0.26%。相比于未处理的电池,开路电压提升了5%,短路电流提升了55.7%,光电转换效率提升了52.9%,后二者均有显著的提升。这归因于DMF处理后的薄膜晶粒与晶粒之间裂缝消失,使薄膜变得更加致密平整,载流子在晶界处复合减少;DFM处理后也使载流子寿命变长,使载流子具有更远的扩散距离。电子和空穴被有效的萃取,减少了复合,从而提升光电转换效率。DMF的用量为90 μL时,开路电压为0.62 V,短路电流为0.91 mA∙cm−2,光电转换效率为0.23%;DMF的用量为120 μL时,开路电压为0.62 V,短路电流为0.74 mA∙cm−2,光电转换效率为0.18%。DMF的用量增多时电池的性能逐渐降低,这是由于过量的DMF将部分薄膜溶解,导致空穴传输层和电子传输层直接接触,电子和空穴不能有效分离。

(a) (b)

Figure 5. (a) I-V curves of complete devices processed with different amounts of DMF; (b) device performance of films with 60 µLDMF processing.

图5. (a)不同量DMF处理的完整器件效率图;(b) 60 µLDMF处理最优器件性能

Table 2. Parameters of solar cell performance with DMF enhanced MBI films

表2. MBI电池的性能参数

4. 结论

本文在两步蒸镀、掺氯的基础上,探索了DMF溶剂气氛处理对MBI薄膜的影响,系统研究了DMF的用量对改善MBI钙钛矿太阳能电池性能的作用。研究表明,DMF溶剂气氛退火不仅能够提高薄膜质量,增大晶粒,消除晶粒与晶粒之间的裂缝使薄膜变得致密平整,还能够增加薄膜的光吸收,减少薄膜内部缺陷,增加载流子寿命。在最优条件下,即用60 μL DMF处理MBI薄膜,制备的薄膜粗糙度为14 nm,器件性能达到最好,短路电流和光电转换效率相对于原始器件都有显著提升,光电转换效率为0.26%,比未处理的提升了52.9%。

基金项目

本研究由国家自然科学基金(51602096、11374091、11574076、11674087)、湖北省科技厅(2018CFA026)、

武汉市科技局(2018010401011268)和高校学科创新引智计划(111项目,D18025)资助。

NOTES

*通讯作者。

文章引用:
艳领, 王星辰, 孙振兴, K. P. Homewood, 高云, 雷丙龙. 溶剂退火制备高质量MA3Bi2I9钙钛矿薄膜与太阳能电池[J]. 材料科学, 2020, 10(1): 31-39. https://doi.org/10.12677/MS.2020.101005

参考文献

[1] Kojima, A., Teshima, K., Shirai, Y. and Miyasaka, T. (2009) Organometal Halide Perovskites as Visible-Light Sensi-tizers for Photovoltaic Cells. Journal of the American Chemical Society, 131, 6050-6051.
https://doi.org/10.1021/ja809598r
[2] Kim, M., Kim, G.-H., Lee, T.K., Choi, I.W., Choi, H.W., Jo, Y., Yoon, Y.J., Kim, J.W., Lee, J., Huh, D., Lee, H., Kwak, S.K., Kim, J.Y. and Kim, D.S. (2019) Methylammonium Chloride Induces Intermediate Phase Stabilization for Efficient Perovskite Solar Cells. Joule, 3, 2179-2192.
https://doi.org/10.1016/j.joule.2019.06.014
http://www.sciencedirect.com/science/article/pii/S2542435119303058
[3] Li, X., Liu, Y., Eze, V.O., Mori, T., Huang, Z., Homewood, K.P., Gao, Y. and Lei, B. (2019) Amorphous Na-noporous WOx Modification for Stability Enhancement and Hysteresis Reduction in TiO2-Based Perovskite Solar Cells. Solar Energy Materials and Solar Cells, 196, 157-166.
https://doi.org/10.1016/j.solmat.2019.03.040
http://www.sciencedirect.com/science/article/pii/S092702481930159X
[4] Jiang, Q., Zhao, Y., Zhang, X., Yang, X., Chen, Y., Chu, Z., Ye, Q., Li, X., Yin, Z. and You, J. (2019) Surface Passivation of Perovskite Film for Efficient Solar Cells. Nature Photonics, 13, 460-466.
https://doi.org/10.1038/s41566-019-0398-2
[5] Gao, P., Grätzel, M. and Nazeeruddin, M.K. (2014) Organohalide Lead Perovskites for Photovoltaic Applications. Energy & Environmental Science, 7, 2448-2463.
https://doi.org/10.1039/C4EE00942H
[6] Hao, F., Stoumpos, C.C., Cao, D.H., Chang, R.P.H. and Kanatzidis, M.G. (2014) Lead-Free Solid-State Organic-Inorganic Halide Perovskite Solar Cells. Nature Photonics, 8, 489-494.
https://doi.org/10.1038/nphoton.2014.82
[7] Noel, N.K., Stranks, S.D., Abate, A., Wehrenfennig, C., Guarnera, S., Haghighirad, A.-A., Sadhanala, A., Eperon, G.E., Pathak, S.K., Johnston, M.B., Petrozza, A., Herz, L.M. and Snaith, H.J. (2014) Lead-Free Organic-Inorganic Tin Halide Perovskites for Photovoltaic Applications. Energy & Environmental Science, 7, 3061-3068.
https://doi.org/10.1039/C4EE01076K
[8] Park, B.-W., Philippe, B., Zhang, X., Rensmo, H., Boschloo, G. and Johansson, E.M.J. (2015) Bismuth Based Hybrid Perovskites A3Bi2I9 (A: Methylammonium or Cesium) for Solar Cell Application. Advanced Materials, 27, 6806-6813.
https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201501978
https://doi.org/10.1002/adma.201501978
[9] Zhao, Z., Gu, F., Li, Y., Sun, W., Ye, S., Rao, H., Liu, Z., Bian, Z. and Huang, C. (2017) Mixed-Organic-Cation Tin Iodide for Lead-Free Perovskite Solar Cells with an Efficiency of 8.12%. Advanced Science, 4, Article ID: 1700204.
https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.201700204
https://doi.org/10.1002/advs.201700204
[10] Wang, F., Ma, J., Xie, F., Li, L., Chen, J., Fan, J. and Zhao, N. (2016) Organic Cation-Dependent Degradation Mechanism of Organotin Halide Perovskites. Advanced Functional Materials, 26, 3417-3423.
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201505127
https://doi.org/10.1002/adfm.201505127
[11] Vigneshwaran, M., Ohta, T., Iikubo, S., Kapil, G., Ripolles, T.S., Ogomi, Y., Ma, T., Pandey, S.S., Shen, Q., Toyoda, T., Yoshino, K., Minemoto, T. and Hayase, S. (2016) Facile Syn-thesis and Characterization of Sulfur Doped Low Bandgap Bismuth Based Perovskites by Soluble Precursor Route. Chemistry of Materials, 28, 6436-6440.
https://doi.org/10.1021/acs.chemmater.6b02315
[12] Lehner, A.J., Fabini, D.H., Evans, H.A., Hébert, C.-A., Smock, S.R., Hu, J., Wang, H., Zwanziger, J.W., Chabinyc, M.L. and Seshadri, R. (2015) Crystal and Electronic Structures of Complex Bismuth Iodides A3Bi2I9 (A = K, Rb, Cs) Related to Perovskite: Aiding the Rational Design of Photovoltaics. Chemistry of Materials, 27, 7137-7148.
https://doi.org/10.1021/acs.chemmater.5b03147
[13] Lyu, M., Yun, J.-H., Cai, M., Jiao, Y., Bernhardt, P.V., Zhang, M., Wang, Q., Du, A., Wang, H., Liu, G. and Wang, L. (2016) Organic-Inorganic Bismuth (III)-Based Material: A Lead-Free, Air-Stable and Solution-Processable Light-Absorber beyond Organolead Perovskites. Nano Research, 9, 692-702.
https://doi.org/10.1007/s12274-015-0948-y
[14] Kulkarni, A., Singh, T., Ikegami, M. and Miyasaka, T. (2017) Photovoltaic Enhancement of Bismuth Halide Hybrid Perovskite by N-methyl Pyrrolidone-Assisted Morphology Conversion. RSC Advances, 7, 9456-9460.
https://doi.org/10.1039/C6RA28190G
[15] Jain, S.M., Phuyal, D., Davies, M.L., Li, M., Philippe, B., De Castro, C., Qiu, Z., Kim, J., Watson, T., Tsoi, W.C., Karis, O., Rensmo, H., Boschloo, G., Edvinsson, T. and Durrant, J.R. (2018) An Effective Approach of Vapour Assisted Morphological Tailoring for Reducing Metal Defect Sites in Lead-Free, (CH3NH3)3Bi2I9 Bismuth-Based Perovskite Solar Cells for Improved Performance and Long-Term Stability. Nano Energy, 49, 614-624.
http://www.sciencedirect.com/science/article/pii/S2211285518303197
https://doi.org/10.1016/j.nanoen.2018.05.003
[16] Lan, C., Luo, J., Zhao, S., Zhang, C., Liu, W., Hayase, S. and Ma, T. (2017) Effect of Lead-Free (CH3NH3)3Bi2I9 Perovskite Addition on Spectrum Absorption and Enhanced Pho-tovoltaic Performance of Bismuth Triiodide Solar Cells. Journal of Alloys and Compounds, 701, 834-840.
https://doi.org/10.1016/j.jallcom.2017.01.169
http://www.sciencedirect.com/science/article/pii/S0925838817301925
[17] Ran, C., Wu, Z., Xi, J., Yuan, F., Dong, H., Lei, T., He, X. and Hou, X. (2017) Construction of Compact Me-thylammonium Bismuth Iodide Film Promoting Lead-Free Inverted Planar Heterojunction Organohalide Solar Cells with Open-Circuit Voltage over 0.8 V. The Journal of Physical Chemistry Letters, 8, 394-400.
https://doi.org/10.1021/acs.jpclett.6b02578
[18] Abulikemu, M., Ould-Chikh, S., Miao, X., Alarousu, E., Murali, B., Ngongang Ndjawa, G.O., Barbé, J., El Labban, A., Amassian, A. and Del Gobbo, S. (2016) Optoelectronic and Photovoltaic Properties of the Air-Stable Organohalide Semiconductor (CH3NH3)3Bi2I9. Journal of Materials Chemistry A, 4, 12504-12515.
https://doi.org/10.1039/C6TA04657F
[19] Mali, S.S., Kim, H., Kim, D.-H. and Kook Hong, C. (2017) Anti-Solvent Assisted Crystallization Processed Methylammonium Bismuth Iodide Cuboids towards Highly Stable Lead-Free Perovskite Solar Cells. Chemistry Select, 2, 1578-1585.
https://onlinelibrary.wiley.com/doi/abs/10.1002/slct.201700025
https://doi.org/10.1002/slct.201700025
[20] Zhang, X., Wu, G., Gu, Z., Guo, B., Liu, W., Yang, S., Ye, T., Chen, C., Tu, W. and Chen, H. (2016) Active-Layer Evolution and Efficiency Improvement of (CH3NH3)3Bi2I9-Based Solar Cell on TiO2-Deposited ITO Substrate. Nano Research, 9, 2921-2930.
https://doi.org/10.1007/s12274-016-1177-8
[21] Zhang, Z., Li, X., Xia, X., Wang, Z., Huang, Z., Lei, B. and Gao, Y. (2017) High-Quality (CH3NH3)3Bi2I9 Film-Based Solar Cells: Pushing Efficiency up to 1.64%. The Journal of Physical Chemistry Letters, 8, 4300-4307.
https://doi.org/10.1021/acs.jpclett.7b01952
[22] 李晓伟, 刘艳领, Homewood, K.P., 黄忠兵, 高云, 雷丙龙. 两步蒸镀法制备高质量(CH3NH3)3Bi2I9钙钛矿薄膜[J]. 材料科学, 2019(9): 115.
[23] Lee, L.C., Huq, T.N., MacManus-Driscoll, J.L. and Hoye, R.L.Z. (2018) Research Update: Bis-muth-Based Perovskite-Inspired Photovoltaic Materials. APL Materials, 6, Article ID: 084502.
https://aip.scitation.org/doi/abs/10.1063/1.5029484
https://doi.org/10.1063/1.5029484