A case including a case main body, a matrix including a semiconductor nanocrystal, the matrix disposed in the case main body, and a sealant disposed on the case main body, wherein the sealant has a gas permeability of about 1 cubic centimeter at standard temperature and pressure per centimeter per meter squared per day per atmosphere or less and a tensile strength of about 5 megaPascals or more, and wherein the semiconductor nanocrystal is a Group II-VI compound, a Group III-V compound, a Group IV-VI compound, a Group IV element, a Group IV element, a Group IV compound, or a combination thereof.