The entropy and/or temperature change of material with respect to electric fields is known as electrocaloric effect (ECE). Giant ECE is discovered in P(VDF-TrFE) ferroelectric copolymers near ferroelectric-paraelectric (F-P) transition temperature. F-P transition is normally much higher than room temperature around which is preferred by working temperature of cooling device configuration. This paper presents the two defect-inducing methods to lower and broaden working temperature range of P(VDF-TrFE) based copolymers for ECE. Giant ECE is experimentally demonstrated in large temperature range (0-55°C). In addition, an electrocaloric oscillatory refrigerator (ECOR) was proposed and simulated by finite volume method and its high performance was theoretically demonstrated. Temperature gradient larger than 30 °C can be maintained across the two sides of a 1 cm device. For ΔT=20 °C cooling condition, a high cooling power (5.4 W/cm 2) and significantly higher coefficient of performance (COP) can be achieved (50% of Carnot efficiency).