Yao Disheng, Zhang Chunmei, Pham Ngoc Duy, Zhang Yaohong, Tiong Vincent Tiing, Du Aijun, Shen Qing, Wilson Gregory J, Wang Hongxia
School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty , Queensland University of Technology , Brisbane , Australia.
Faculty of Informatics and Engineering , The University of Electro-Communications , 1-5-1 Chofugaoka , Chofu, Tokyo 182-8585 , Japan.
J Phys Chem Lett. 2018 Apr 19;9(8):2113-2120. doi: 10.1021/acs.jpclett.8b00830. Epub 2018 Apr 12.
Organic-inorganic hybrid lead halide perovskite solar cells have demonstrated competitive power conversion efficiency over 22%; nevertheless, critical issues such as unsatisfactory device stability, serious current-voltage hysteresis, and formation of photo nonactive perovskite phases are obstacles for commercialization of this photovoltaics technology. Herein we report a facial yet effective method to hinder formation of photoinactive δ-FAPbI and hysteresis behavior in planar heterojunction perovskite solar cells based on K (MAFA)PbIBr (0≤ x ≤ 0.1) through incorporation of potassium ions (K). X-ray diffraction patterns demonstrate formation of photoinactive δ-FAPbI was almost completely suppressed after K incorporation. Density functional theory calculation shows K prefers to enter the interstitial sites of perovskite lattice, leading to chemical environmental change in the crystal structure. Ultrafast transient absorption spectroscopy has revealed that K incorporation leads to enhanced carrier lifetime by 50%, which is also confirmed by reduced trap-assisted recombination of the perovskite solar cells containing K in photovoltage decay. Ultraviolet photoelectron spectroscopy illustrates that K incorporation results in a significant rise of conduction band minimum of the perovskite material by 130 meV, leading to a more favorable energy alignment with electron transporting material. At the optimal content of 3% K (molar ratio, relative to the total monovalent cations), nearly hysteresis-free, enhanced power conversion efficiencies from 15.72% to 17.23% were obtained in this solar cell.
有机-无机杂化铅卤化物钙钛矿太阳能电池已展现出超过22%的具有竞争力的功率转换效率；然而，诸如器件稳定性不尽人意、严重的电流-电压滞后现象以及光非活性钙钛矿相的形成等关键问题，是这项光伏技术商业化的障碍。在此，我们报告一种简便而有效的方法，通过引入钾离子（K）来阻碍基于K(MAFA)PbIBr（0≤x≤0.1）的平面异质结钙钛矿太阳能电池中光非活性δ-FAPbI的形成及滞后行为。X射线衍射图谱表明，引入K后，光非活性δ-FAPbI的形成几乎被完全抑制。密度泛函理论计算表明，K倾向于进入钙钛矿晶格的间隙位置，导致晶体结构中的化学环境发生变化。超快瞬态吸收光谱表明，引入K使载流子寿命提高了50%，这在含K的钙钛矿太阳能电池光电压衰减中的陷阱辅助复合减少中也得到了证实。紫外光电子能谱表明，引入K使钙钛矿材料的导带最小值显著提高了130毫电子伏特，导致与电子传输材料形成更有利的能量排列。在3%K（摩尔比，相对于总单价阳离子）的最佳含量下，该太阳能电池获得了几乎无滞后、功率转换效率从15.72%提高到17.23%的效果。
