A light-emitting electrochemical cell comprising a first electrode, a second electrode, and at least one light-emitting active material comprising a combination of an electrolyte, a first constituent comprising a host compound and a second constituent comprising a guest compound. A quotient between a difference in LUMO energy level between the first and second constituent, Etrapn, and a difference in HOMO energy level between the second and first constituent, Etrapp, is 1/10 to 10, a quotient between an electron mobility and a hole mobility on the first constituent is 1/100 to 100, a quotient between a number of ions of the electrolyte and a number of molecules or repeat units of the second constituent is ⅓ to 5, and a LUMO energy level of the electrolyte is higher than the LUMO energy level of the first constituent and a HOMO energy level of the electrolyte is lower than the HOMO energy level of the first constituent.