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研究了阴离子和阳离子混合型碘系钙钛矿薄膜材料的结构、光学性质及光致发光温度特性. 研究发现, 阴离子混合型碘系钙钛矿( MAPb(Br x I 1–x) 3, MA +=
$ {\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{NH}}_3^ + $ )随着半径较小的Br –离子的比例增加( x= 0—0.1), 薄膜择优取向生长更明显, 其光学带隙从1.43 eV到1.48 eV线性增加. 在光抽运下, 随着工作温度从10 K升高到125 K, 纯碘系钙钛矿( MAPbI 3, 即 x= 0)可见区光致发光(PL)的峰位轻微的红移; 之后至350 K, 发生蓝移. 而Br –阴离子混合型钙钛矿薄膜的PL峰位只随温度升高持续蓝移. 并且在不同工作温度下, Br –阴离子比例 x与PL峰位呈现线性关系. 对于纯碘系钙钛矿, 其高温段激子结合能是37.5 meV; 随着Br –的比例的增加, 高温段激子结合能会先增大后减小. 当 x= 0.0333, 其薄膜PL半高宽随温度升高展宽幅度最小, 具有更好的温度稳定性. 通过进一步三重阳离子混合和阴离子调节, 获得更加优良的混合型碘系钙钛矿((Cs 0.05( FA 0.85 MA 0.15) 0.95)Pb(Br 0.15I 0.85) 3, FA +=$ {\rm{HC}}({\rm{N}}{{\rm{H}}_2})_2^ +$ )薄膜, 为进一步研制太阳能电池和发光器件奠定了实验基础.Lead halide perovskite has attracted much attention due to its high absorption coefficient, long carrier diffusion length, low binding energy, and low cost. The stability of intrinsic crystal structure in I-based perovskite can be theoretically estimated by calculating cubic structures factor and octahedral factor. Experimental methods to solve the stability of structure in I-based perovskite could be mainly to either incorporate anions (e.g. Cl –, Br –) or mix cations (e.g. Cs +) into I-based perovskite matrix. Moreover, incorporating Br –into I-based perovskite leads its band gap to widen, which might be used as a top-cell material to tandem solar cell. However, in order to understand photo-physics process of anion-mixed and/or cation-mixed perovskites, it is essential to further investigate the optical properties such as absorption spectrum, photoluminescence (PL), temperature-dependent PL (TPL) behavior, etc. In this work, anion-mixed and/or cation-mixed perovskite thin films with high quality crystallization and (110) prereferral orientation are synthesized by one-step solution method. All mixed perovskite films are characterized by using X-ray diffraction (Rigaku D MAX-3C, Cu-Kα, λ= 1.54050 Å) and X-ray photoelectron spectroscopy (XPS) (Thermo Scientific Escalab 250Xi). A set of strong peaks of the mixed perovskite films at 14.12° and 28.48°, is assigned to (110) and (220) lattice plane of orthorhombic crystal structure of I-based perovskite, due to preferred orientation. The Pb 4f and I 3d doublet peaks, corresponding to Pb +2and I –states, are observed in XPS spectra. It should be noted that in the absence of other valence states of Pb and I component at lower/upper binding energy, the chemical element composition ratio of Pb +2and I –are close to stoichiometric proportion. For optical absorptionspectra, the optical bandgaps of the perovskite films increase with doping concentration of Br –increasing. For TPL, the perovskite films with x= 0 and x= 0.05 show abnormal red-shifts in a temperature range from 10 to 100 K. The following blue shifts in a temperature range from 125 to 350 K emerge, which is mainly attributed to band gap widening. However, incorporating more Br –into I-based perovskite leads the TPL spectra to monotonically blue-shift. A linear relationship between the TPL peak position and the doping concentration of Br –ions is observed at the same temperatures. This indicates that the Br –anion in I-based perovskite plays a crucial role in determining the optical properties. The low-temperature and high-temperature (HT) excitonic binding energy at x= 0 are 186 meV and 37.5 meV, respectively. The HT excitonic binding energy first increases and then decreases with the Br –concentration in I-based perovskite film increasing. The minimal variation of TPL peak position and FWHM (full width at half maximum) at x= 0.0333 are 13 nm and (25.8 ± 0.5) meV, respectively, suggesting higher temperature stability in optical property. This should contribute to understanding the relationship between temperature-dependent electrical and optoelectronic performance for hybrid mixed perovskite materials and devices.-
Keywords:
- hybrid mixed perovskite/
- temperature-dependent photoluminescence/
- optical properties/
- excitonic binding energy
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] -
Pb/I原子比 样品化学式 XPS测得成分 26.42/73.58 $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9833}}{\rm{B}}{{\rm{r}}_{0.0167}}} \right)_3}$ $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.97}}{\rm{B}}{{\rm{r}}_{0.03}}} \right)_3}$ 26.84/73.16 $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9667}}{\rm{B}}{{\rm{r}}_{0.0333}}} \right)_3}$ $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9467}}{\rm{B}}{{\rm{r}}_{0.0533}}} \right)_3}$ 27/73 $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9333}}{\rm{B}}{{\rm{r}}_{0.0667}}} \right)_3}$ $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9367}}{\rm{B}}{{\rm{r}}_{0.0633}}} \right)_3}$ 27.55/72.45 $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9}}{\rm{B}}{{\rm{r}}_{0.1}}} \right)_3}$ $ MA{\rm{Pb}}{\left( {{{\rm{I}}_{0.9133}}{\rm{B}}{{\rm{r}}_{0.0667}}} \right)_3}$ 
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[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38]
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