Do Capacitance Measurements Reveal Light-Induced Bulk Dielectric Changes in Photovoltaic Perovskites?,The Journal of Physical Chemistry C

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Do Capacitance Measurements Reveal Light-Induced Bulk Dielectric Changes in Photovoltaic Perovskites?
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-12-30 00:00:00 , DOI: 10.1021/acs.jpcc.7b11703
Osbel Almora _{1,

2} , Clara Aranda ₁ , Germà Garcia-Belmonte ₁

Affiliation

Several studies have identified complex interactions between photogenerated carriers and the crystal lattice in perovskite materials for photovoltaics, which are regarded to have an inherently soft character. Light is known to induce phase segregation in mixed halide perovskites, enhance piezoelectricity, and change dipole moments of the unit cell. Therefore, it is appealing to consider photogenerated variations in the bulk polarizability and dielectric properties. Light-induced bulk polarization changes should be observable by capacitance measurements, preferentially at intermediate frequencies where the geometrical capacitance dominates. However, capacitance spectra are influenced by several capacitive and resistive mechanisms, which are also modulated by light. Capacitances may arise from dielectric bulk polarization, space-charge depletion zones, chemical electronic bulk storage, and interfacial accumulation mechanisms. This variety of capacitive mechanisms may induce wrong interpretations and produce misleading outcomes when uncritically connected to the bulk polarization response. It is shown here how capacitance–voltage analyses performed at a given frequency are influenced by overlapping effects that mask the actual value of the geometrical capacitance. Careful analyses are then needed before attributing the light-induced modulation of the measured capacitance to hybrid perovskite dielectric changes.

中文翻译：

电容测量结果能揭示光致钙钛矿中光诱导的介电常数的变化吗？

几项研究已经确定了用于光伏的钙钛矿材料中光生载流子与晶格之间的复杂相互作用，这些相互作用被认为具有固有的软性。已知光会引起混合卤化物钙钛矿中的相分离，增强压电性并改变晶胞的偶极矩。因此，考虑在体极化率和介电性质方面的光生变化是有吸引力的。光感应的体极化变化应通过电容测量来观察，最好在几何电容占主导的中频处观察。但是，电容频谱受几种电容和电阻机制的影响，这些机制也受光调制。电介质的体极化可能会引起电容，空间电荷耗尽区，化学电子大容量存储和界面堆积机制。当不加批判地连接到体极化响应时，多种电容机制可能会引起错误的解释并产生误导性的结果。此处显示了在给定频率下执行的电容-电压分析如何受到重叠效应的影响，这些重叠效应掩盖了几何电容的实际值。在将测得电容的光感应调制归因于钙钛矿杂化介质杂化变化之前，需要进行仔细的分析。此处显示了在给定频率下执行的电容-电压分析如何受到重叠效应的影响，这些重叠效应掩盖了几何电容的实际值。在将测得电容的光感应调制归因于钙钛矿杂化介质杂化变化之前，需要进行仔细的分析。这里显示了在给定频率下执行的电容-电压分析如何受到重叠效应的影响，这些重叠效应掩盖了几何电容的实际值。在将测得电容的光感应调制归因于钙钛矿杂化介质杂化变化之前，需要进行仔细的分析。

更新日期：2017-12-30

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