Mastroianni S, Heinz F D, Im J-H, Veurman W, Padilla M, Schubert M C, Würfel U, Grätzel M, Park N-G, Hinsch A
Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg, Germany.
Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Nanoscale. 2015 Dec 14;7(46):19653-62. doi: 10.1039/c5nr05308k.
CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as well as light beam induced current measurements (LBIC). It was found that the most efficient cell shows the highest luminescence and the least efficient cell is most strongly limited by non-radiative recombination. Crystal size, morphology and distribution in the capping layer and in the porous scaffold strongly affect the non-radiative recombination. Moreover, the very non-uniform crystal structure with multiple facets, as evidenced by SEM images of the 0.032 M device, suggests the creation of a large number of grain boundaries and crystal dislocations. These defects give rise to increased trap-assisted non-radiative recombination as is confirmed by high-resolution μ-PL images. The different imaging techniques used in this study prove to be well-suited to spatially investigate and thus correlate the crystal morphology of the perovskite layer with the electrical and radiative properties of the solar cells and thus with their performance.
研究了具有介孔TiO₂层和作为空穴传输层（HTL）的螺环-MeOTAD的CH₃NH₃PbI₃钙钛矿太阳能电池，其CH₃NH₃I浓度有三种不同值（0.032 M、0.044 M和0.063 M）。观察到晶体尺寸和形态的强烈变化，导致电池效率多样化（分别为9.2%、16.9%和12.3%）。通过将电流-电压曲线与光致发光和电致发光（PL和EL）成像以及光束诱导电流测量（LBIC）相结合的详细表征，分析了这种行为的物理起源。发现效率最高的电池发光最强，而效率最低的电池受非辐射复合的限制最大。覆盖层和多孔支架中的晶体尺寸、形态和分布强烈影响非辐射复合。此外，0.032 M器件的SEM图像证明，具有多个面的非常不均匀的晶体结构表明产生了大量的晶界和晶体位错。高分辨率μ-PL图像证实，这些缺陷导致陷阱辅助非辐射复合增加。本研究中使用的不同成像技术被证明非常适合于空间研究，从而将钙钛矿层的晶体形态与太阳能电池的电学和辐射特性以及它们的性能联系起来。
