The objective of this work is to quantitatively characterize the 3D complexity of ZnO : TiO ₂-organic blended solar cells layers by atomic force microscopy and fractal analysis. ZnO : TiO ₂-organic blended solar cells layers were investigated by AFM in tapping-mode in air, on square areas of 25 μm². A detailed methodology for ZnO : TiO ₂-organic blended solar cells layers surface fractal characterization, which may be applied for AFM data, is presented. Detailed surface characterization of the surface topography was obtained using statistical parameters, according with ISO 25178-2: 2012. The fractal dimensions D_f values (all with average ± standard deviation), obtained with morphological envelopes method, for: blend D1 ( P 3 HT : PCBM : ZnO : TiO ₂ blend with ratio 1:0.35:0.175:0.175 mg in 1 ml of Chlorobenzene) is D_f = 2.55 ± 0.01; and for blend D2 ( P 3 HT : PCBM : ZnO : TiO ₂ blend with ratio 1:0.55:0.075:0.075 mg in 1 ml of Chlorobenzene) is D_f = 2.45 ± 0.01. Denoting the ratios in 1 ml of Chlorobenzene with D1 and D2 articles. The 3D surface roughness of samples revealed a fractal structure at nanometer scale. Fractal and AFM analysis may assist manufacturers in developing ZnO : TiO ₂-organic blended solar cells layers with better surface characteristics and provides different yet complementary information to that offered by traditional surface statistical parameters.