Enhanced diode characteristics of organic solar cells using titanium suboxide electron transport layer

The (dark) diode characteristics of the organic bulk heterojunction solar cell based on the phase separated blend of poly[N-9 ''-heptadecanyl-2,7-carbazole-alt-5,5-(4', 7'-di-2-thenyl-2', 1', 3'-benzothiadiazole )] with [6,6]-phenyl C(70)-butyric acid methyl ester have been analyzed with a focus on the effect of the titanium suboxide (TiO(x)) electron transport layer. The addition of the TiO(x) layer into the device structure causes the saturation current density to decrease by a factor of 26 and the shunt resistance to increase by a factor of 12. The diode ideality factor and series resistance are, respectively, almost the same for diodes made with and without the TiO(x) layer. The results indicate that the TiO(x) layer increases the energy barrier for hole transport and reduces the minority carrier density. (C) 2010 American Institute of Physics. [doi:10.1063/1.3409116]