Supplementary material (ESI) for Journal of Materials Chemistry This journal is © The Royal Society of Chemistry 2008 1 Supporting Information Perovskite Hollow Cubes: Morphological Control, Three-dimensional Twinning and Intensely Enhanced Photoluminescence Xianfeng Yang, Ian D. Williams, Jian Chen, Jing Wang, Huifang Xu, Hiromi Konishi, Yuexiao Pan, Chaolun Liang and Mingmei Wu* * To whom correspondence should be addressed