Advanced Materials

Biography

Biography: Wing Chung Tsoi

Abstract

Perovskite solar cells (PSCs) are very attractive for next generation solar cells, which can be solution processed in simple ways and imply the fabrication can be at very low cost by scalable printing/coating methods. Besides, power conversion efficiency (PCE) as high as ~22% has been recently demonstrated. However, the key challenge is their generally low stability. It is important to probe and understand the degradation products and how these products affect its functionality. On the other hand, passivation effect on perovskite solar material is important as it could increase its PCE and improve its stability. It is therefore also important to probe and understand the passivation effect as well e.g. by small additional amount of Lead Iodide (PbI₂). Raman spectroscopy is a powerful technique which could be used to identify and quantify chemical species, including degradation products from PSCs, such as PbI₂. However, it does not answer questions such as how the formation of PbI₂ affects its photo-physical properties (e.g. photoluminescence (PL)) and photocurrent generation. Here, we developed a simultaneous multi-mapping technique (Raman, PL, and photocurrent mapping) with spatial resolution of ~ 1 µm. This novel and advanced technique allows study on how the degradation product affect is local PL and photocurrent (ion migration). As examples, we show here the effect of dark electrical bias on PSCs and selective photo-degradation (and also likely photo-passivation) of PSCs. The unique information is difficult to be obtained by other characterization techniques, and could be extended to study other type of solar cells.