Improving the performance of the organic solar cell and the inorganic heterojunction devices using monodisperse Fe3O4 nanoparticles

8 nm Fe3O4 nanoparticles (NPs) were successfully doped into poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) to fabricate ITO/PEDOT:PSS/P3HT:PCBM:Fe3O4/Al solar cell along with a heterojunction device of Fe3O4/p-GaAs by depositing them on p-GaAs substrates. The experimental results revealed that the presence of Fe3O4 nanoparticles (NPs) in the ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell improved its performance with respect to the one without Fe3O4. For example, power conversion efficiency was increased from 1.09% to 2.22% when doping 5 wt% of Fe3O4 NPs to P3HT:PCBM. This was attributed to increase of the light absorption in the presence of Fe3O4 NPs doping. Furthermore, the analysis of the current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) characteristics of the Fe3O4/p-GaAs heterojunction have been studied successfully. The experimental barrier height Φb and ideality factor n were determined as 0.80 eV and 1.53, respectively, from the experimental I-V plots. In addition, the value of the Φb obtained from the C-V characteristics was 0.95 eV (f = 500 kHz). The mismatch between barrier heights obtained from both measurements was explained by the two techniques are based on different nature. The interface state density of the Fe3O4/p-GaAs heterojunction was determined from 5.16 × 1014 cm−2eV-1 to 1.34 × 1015 cm−2eV−1.