Organic small molecule solar cells with a homogeneously mixed copper phthalocyanine: C60 active layer

Abstract

An efficient organic solar cell with a vacuum codeposited donor–acceptor copper phthalocyanine $({\mathrm{CuPc):C}}_{60}$ mixed layer is described. A device with a structure of indium tin oxide/330 Å ${\mathrm{CuPc:C}}_{60}\text{(1:1)/100}$ Å ${\mathrm{C}}_{60}\text{/75}$ Å 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/Ag has a series resistance of only $R_S\text{=0.25\hspace{0.5em}Ω\hspace{0.05em}}{\mathrm{cm}}^2,$ resulting in a current density of ∼1 ${\mathrm{A/cm}}^2$ at a forward bias of +1 V, and a rectification ratio of ${10}^6$ at ±1 V. Under simulated solar illumination, the short circuit current density increases linearly with light intensity up to 2.4 suns. The maximum power conversion efficiency is ${\eta }_P\text{=(3.6±0.2)\%}$ at 0.3 suns (AM1.5G simulated solar spectrum) and ${\eta }_P\text{=(3.5±0.2)\%}$ at 1 sun. Although the fill factor decreases with increasing intensity, a power efficiency as high as ${\eta }_P\text{=(3.3±0.2)\%}$ is observed at 2.4 suns intensity.