Time-resolved photoluminescence is a validated method for tracking the photoexcited carrier dynamics in luminescent materials. This technique probes the photoluminescence decays upon a periodic excitation by short laser pulses. Herein, we show that this approach cannot directly detect hidden photoexcitations with much slower dynamics than the photoluminescence decay. We demonstrate a new method based on a multipulse excitation scheme that enables an unambiguous detection and an easily interpreted tracking of these hidden species. The multipulse excitation consists of a single pulse (Read) followed by a burst of many closely separated pulses (Write) and finally another single pulse (Read). To illustrate the efficacy of the Read-Write-Read excitation scheme, we apply it to metal halide perovskites to directly visualize carrier trapping, extract the concentration of trapped charges, and determine the rate constant of trap depopulation. The developed approach allows studying performance-limiting processes in energy devices using a versatile, highly applicable all-optical method.

中文翻译：

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通过多脉冲光致发光探测的隐藏光激发


时间分辨光致发光是一种经过验证的方法，用于跟踪发光材料中的光激发载流子动力学。该技术探测光致发光在短激光脉冲的周期性激发下衰减。在此，我们表明这种方法不能直接检测隐藏的光激发，其动力学速度比光致发光衰减慢得多。我们展示了一种基于多脉冲激发方案的新方法，该方法能够对这些隐藏的物质进行明确检测和易于解释的跟踪。多脉冲激励由一个脉冲 （Read） 组成，然后是许多紧密分离的脉冲 （Write），最后是另一个单脉冲 （Read）。为了说明读-写-读激发方案的有效性，我们将其应用于金属卤化物钙钛矿，以直接可视化载流子俘获，提取俘获电荷的浓度，并确定陷阱减少的速率常数。开发的方法允许使用通用、高度适用的全光学方法研究能源设备中的性能限制过程。