Quantum dot semiconductor nanoparticle compositions that incorporate ions such as zinc, aluminum, calcium, or magnesium into the quantum dot core have been found to be more stable to Ostwald ripening. A core-shell quantum dot may have a core of a semiconductor material that includes indium, magnesium, and phosphorus ions. Ions such as zinc, calcium, and/or aluminum may be included in addition to, or in place of, magnesium. The core may further include other ions, such as selenium, and/or sulfur. The core may be coated with one (or more) shells of semiconductor material. Example shell semiconductor materials include semiconductors containing zinc, sulfur, selenium, iron and/or oxygen ions.