Structural and electrical properties of mixture based on P3HT:PCBM and low band gap naphthalene diimide-imines

Three small organic molecules, namely naphthalene diimide-imines, were investigated by electrical techniques and theoretically calculated by density functional theory. Electrical properties of the devices were tested in dark and under illumination. Nyquist plots were presented for devices measured by impedance spectroscopy. Additionally, compounds were investigated by ultraviolet–visible spectroscopy and atomic force microscopy. The obtained results showed that chemical structure of the organic compound and device architecture influence on the electrical properties of organic solar cells. The device comprising 5% w/w of naphthalene diimide-imine end-capped with bithiophene units in layer consist of poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl C61 butyric acid methyl ester showed lower value of power conversion efficiency in comparison with the device comprising 33% w/w of this compound in active layer. Up to now to our best knowledge, there is no any study concerns the properties of the solar cell constructed with such type of molecules as an additive.