engleski

Morphology related energy losses in small molecule organic solar cells

Small molecule organic solar cells have achieved PCE values up to an order of magnitude higher in the past decade, which further signifies their potential for light-weight, cost efficient flexible solar panel fabrication [1]. A promising group of small molecule electron donors for photovoltaic application were shown to be squaraine derivatives (SQ), as they have tunable bandgaps, easy synthesis routes and excellent absorption coefficient as well as good thermal stability [2]. Here we report on hybrid organic solar cells fabricated from various squaraine derivatives synthesized without catalysts. Laboratory scale devices (ITO/ZnO/SQ:PC71BM/MoO3/Ag) were fabricated with various morphologies of the active layer and characterized to gain deeper insight into the charge carrier transport through the cell. Electrical characterization (J/V measurements, light intensity dependence measurements, impendance spectroscopy) confirmed that the degree of phase separation and domain size influence greatly the charge accumulation and recombination mechanisms in the cells. Furthermore, the morphology and phase separation of the thin films were studied by TEM, AFM (KPFM, phase and height) and ToF-SIMS which were, coupled with X-ray scattering, diffraction and UV-VIS spectra, correlated to electrical data and overall performance.

Squaraines, morphology, bulk heterojunction

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