Thin film encapsulation for flexible organic solar cells

We report a damage-free thin-film encapsulation (TFE) for flexible small molecule based photovoltaic devices. The damage to organic PV layers arises during the sputtering deposition of Al₂O₃ and ultraviolet (UV) curing of monomers. To minimize such damage, we insert a buffer layer after evaporating an aluminum cathode. With this scheme, we have fabricated the flexible PV device that consists of ITO(150nm)/CuPc(10nm)/ CuPc:DCM(10nm, 50wt%)/C₆₀:DCM(10nm,50wt%)/ C₆₀(30nm)/Bphen(5nm)/ Al(150nm). To make a comparative analysis, we have fabricated a glass-encapsulated one. It is found that there is no significant discrepancy in the conversion efficiency between them. To demonstrate the barrier property of the TFE, the conversion efficiency as a function of time is observed. It shows that the barrier property of the TFE is comparable with that of the glass encapsulation.