Letian L Dou, Andrew B AB Wong, Yi Y Yu, Minliang M Lai, Nikolay N Kornienko, Samuel W SW Eaton, Anthony A Fu, Connor G CG Bischak, Jie J Ma, Tina T Ding, Naomi S NS Ginsberg, Lin-Wang LW Wang, A Paul AP Alivisatos, Peidong P Yang
Organic-inorganic hybrid perovskites, which have proved to be promising semiconductor materials for photovoltaic applications, have been made into atomically thin two-dimensional (2D) sheets. We report the solution-phase growth of single- and few-unit-cell-thick single-crystalline 2D hybrid perovskites of (C4H9NH3)2PbBr4 with well-defined square shape and large size. In contrast to other 2D materials, the hybrid perovskite sheets exhibit an unusual structural relaxation, and this structural change leads to a band gap shift as compared to the bulk crystal. The high-quality 2D crystals exhibit efficient photoluminescence, and color tuning could be achieved by changing sheet thickness as well as composition via the synthesis of related materials.