Development of high-performance light harvesters is a persistent goal for mesoscopic solar cells. In the current work, lead-free CH3NH3SnBr3-xIx (x = 0-3) perovskite quantum dots (QDs) are made by integrating Br- ions into host crystal structure. Through tuning Br/I ratio, these perovskite-structured QDs are highlighted with tunable optical bandgaps. When applied as light harvesters for mesoscopic solar cell applications, the devices yield reasonable power conversion efficiency and rapid start-up behaviors. An efficiency of 8.79% is achieved for CH3NH3SnBr3-xIx QDs and N719 co-sensitized mesoscopic solar cells. (C) 2018 Elsevier Ltd. All rights reserved.