Mishra Aditya, Hope Michael A, Emsley Lyndon
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland.
ACS Energy Lett. 2024 Sep 25;9(10):5074-5080. doi: 10.1021/acsenergylett.4c02557. eCollection 2024 Oct 11.
Halide perovskites are promising next-generation solar cell materials, but their commercialization is hampered by their propensity to degrade under operating conditions, particularly under heat, humidity, and light. Identifying degradation products and linking them to the degradation mechanism at the atomic scale is necessary to design more stable perovskite materials. Here we use magnetic resonance methods to identify and characterize the formation of both metallic lead clusters and Pb defects upon light-induced degradation of methylammonium lead halide perovskite using nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) measurements. Paramagnetic relaxation enhancement (PRE) of the H NMR resonances demonstrates the presence of localized paramagnetic Pb defects, a large Knight shift of the Pb NMR proves the presence of lead metal, and their relative proportions are determined by the differing temperature dependence in variable-temperature EPR. This work reconciles previous conflicting literature results, enabling the use of EPR spectroscopy to monitor photodegradation of perovskite devices.
卤化物钙钛矿是很有前景的下一代太阳能电池材料，但其商业化受到在工作条件下，特别是在热、湿度和光照下易降解的倾向的阻碍。识别降解产物并在原子尺度上将它们与降解机制联系起来，对于设计更稳定的钙钛矿材料是必要的。在这里，我们使用磁共振方法，通过核磁共振（NMR）和电子顺磁共振（EPR）测量，来识别和表征甲基铵卤化铅钙钛矿光致降解过程中金属铅簇和Pb缺陷的形成。H NMR共振的顺磁弛豫增强（PRE）表明存在局域顺磁Pb缺陷，Pb NMR的大奈特位移证明存在铅金属，并且它们的相对比例由变温EPR中不同的温度依赖性确定。这项工作调和了先前相互矛盾的文献结果，使得能够使用EPR光谱来监测钙钛矿器件的光降解。
