Fabrication, optical, morphological, structural and electrical characterization of organic solar cells based P3HT:PCBM doped with Fe3O4 nanoparticle and mpg-C3N4 nanocomposite

In this Ph.D. thesis, an organic solar cell was produced with P3HT:PCBM photoactive layer and to increase the power conversion efficiency of the organic solar cells, different methods were studied. PEDOT:PSS as the hole transport layer was coated with the spin coating process on ITO and the P3HT:PCBM active layer in the rates, 1:1, 1:0,8 and 1:0,6 were coated on PEDOT:PSS layer using the same method in the glove box. The absorption and AFM, SEM, EDAX, XRD, Raman and XPS measurements of PEDOT:PSS, P3HT, PCBM and P3HT:PCBM layers were carried out. First, using thermal evaporation, Al was coated over the layer of P3HT:PCBM which have different ratios and ITO/PEDOT:PSS/P3HT:PCBM/Al organic solar cell structure was obtained and tested. Then, LiF which has 2 nm thicknes was coated on the active layer using the same method and the effect of LiF layer on the characteristic parameters of ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al organic solar cells was investigated. When the six different samples were examined in both designs, it was seen that without LiF layer, the highest efficiency which is 1,54% was obtained from P3HT:PCBM that has 1:0,8 rate and the power conversation efficiency of LiF layer device that has same contribution rate was 2,74%. After this step, in various designs both the inorganic Fe3O4 nanoparticles and polymer mpg-C3N4 nanocomposite materials in different ratios were doped to P3HT:PCBM photoactive layer to provide a solution to the problems such as short diffusion length, restricted carrier transfer, low carrier mobility, low optic absorbtion intensity and low power conversion efficiency of organic solar cells. It was observed that the power conversion efficiency of ternary P3HT:PCBM:Fe3O4 and P3HT:PCBM:mpg-C3N4 active layer solar cells obtained in the same condition of as the reference the ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al organic solar cell, changed depending on the content ratio. As the result of doped Fe3O4 in different ratios to the active layer, the highest efficiency (4,49%) was obtained in the ratio of 6% and then it was observed that the efficiency was decreased with increase of Fe3O4. In the same way, mpg-C3N4 materials at different rates were doped to P3HT:PCBM. The highest efficiency of 3,70% was obtained with 4% doped mpg-C3N4 and then the efficiency was started to decrease with the increased content ratio. After 7% content ratio, the efficiency value which is lower than the value of reference device was observed. Absorption, AFM, SEM, EDAX, XRD, Raman and XPS measurements of P3HT:PCBM:Fe3O4 and P3HT:PCBM:mpg-C3N4 films were provided considering the contribution rates at which the highest efficiency values were obtained. As a result, it was found that the doped Fe3O4 and mpg-C3N4 are effective at increasing the efficieincy of organic solar cells which cause increase of the absorption intensity.