Non-fullerene organic solar cells have undergone significant improvements via both, synthesis of novel organic synthesis materials and application of easy fabrication methods. However, device degradtion is still a major problem. For example, the peeling-off of the top electrode fabricated by thermal evaporation leads to an intrinsic device degradation, which is one ofamong the main reasons for the performance losses of organic solar cells. Another disadvantage is the inevitable high temperature during the evaporation process, which can be harmful to the organic materials and is energy extensive thereby prolonging the energy payback times significantly. To overcome these challenges, the magnetron sputtering technique appears very promising for top contact deposition.
For understanding the mechanism of the metal cluster growth on the thin films with various morphologies used in organic solar cells, we use apply in-situ grazing-incidence small-angle X-ray scattering (GISAXS) to observe the morphology changes during the sputter depositioning process. In the present study, the active layer of the organic solar cells is composed of the polymer donor PffDT4T-2OD and the small molecule accepter EH-IDTBR. Both materials were dissolved in 1,2,4-trimethylbenzene and chlorobenzene, respectively to obtain different morphologies of the printed PffDT4T-2OD: EH-IDTBR films. Then 10 nm MoO3 was deposited on their surfaceese films, which acts as the electron blocking layer for thein an inverted solar cell devicegeometry. A 20 nm Al layer is sputtered on top of MoO3 acting as top contact. Notably, the formation of the Al electrode on MoO3 is slower than on the active layer without deposition of MoO3. In addition, SEM and AFM measurements indicate that the morphology impacts the Al growth significantly.