Organic solar cells (OSCs) have received considerable attention due to their many merits such as low cost, light weight,and compatibility with large-area and flexible substrates.In add ition,during the past decades, Re-complexes as efficient phosphorescent materials have been applied successful ly in organic light emitting diodes thanks to their chemical and thermal stability,short lifetime and high quantum efficiency.In this paper,we introduce Re(CO)₃Cl(bathocuproine) (Re-BCP) to OSCs as cathode buffer layer.The curren t density-voltage characteristics of the OSCs under AM1.5solar illumination show that the power conversion efficiency depends on the thickness of the buffer layer.Efficie ncy increases at first and then dec reases.When the thickness is 0nm,the efficiency is 0.65%;when the thickness is 7nm,the efficiency is 1.10%;but wh en the thickness increases to 10nm, the efficiency decreases to 0.50%.This can be understood as follows.Thin Re-B CP layer decorated cathode can provide a good ohmic contact and be in favor of electron transport.However,whe n the Re-BCP layer thickness exceeds 10nm,short current denisty and fill fact or will decrease because the electron won′t transport through cathode buffer layer,then the power conversion efficiency decr eases.