Sun Xiaoxiao, Zhang Yong, Ge Weikun
Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600, Duebendorf, Switzerland.
Department of Information Technology and Electrical Engineering, ETH Zurich, 8093, Zurich, Switzerland.
Light Sci Appl. 2022 Sep 7;11(1):262. doi: 10.1038/s41377-022-00957-8.
Contrary to the common belief that the light-induced halide ion segregation in a mixed halide alloy occurs within the illuminated area, we find that the Br ions released by light are expelled from the illuminated area, which generates a macro/mesoscopic size anion ring surrounding the illuminated area, exhibiting a photoluminescence ring. This intriguing phenomenon can be explained as resulting from two counter-balancing effects: the outward diffusion of the light-induced free Br ions and the Coulombic force between the anion deficit and surplus region. Right after removing the illumination, the macro/mesoscopic scale ion displacement results in a built-in voltage of about 0.4 V between the ring and the center. Then, the displaced anions return to the illuminated area, and the restoring force leads to a damped ultra-low-frequency oscillatory ion motion, with a period of about 20-30 h and lasting over 100 h. This finding may be the first observation of an ionic plasma oscillation in solids. Our understanding and controlling the "ion segregation" demonstrate that it is possible to turn this commonly viewed "adverse phenomenon" into novel electronic applications, such as ionic patterning, self-destructive memory, and energy storage.
与混合卤化物合金中光诱导卤离子偏析发生在光照区域内的普遍观点相反，我们发现光释放的溴离子从光照区域排出，这在光照区域周围产生了一个宏观/介观尺寸的阴离子环，呈现出光致发光环。这种有趣的现象可以解释为由两种相互平衡的效应导致：光诱导自由溴离子的向外扩散以及阴离子亏缺区和过剩区之间的库仑力。去除光照后，宏观/介观尺度的离子位移导致环与中心之间产生约0.4V的内建电压。然后，位移的阴离子回到光照区域，恢复力导致阻尼的超低频振荡离子运动，周期约为20 - 30小时，持续超过100小时。这一发现可能是首次在固体中观察到离子等离子体振荡。我们对“离子偏析”的理解和控制表明，有可能将这种通常被视为“不利现象”转化为新型电子应用，如离子图案化、自毁式存储器和能量存储。
