ABSTRACT
We have synthesized water-soluble polymer, poly[(9,9-bis((6'-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene))-alt-bisphenylfumaronitrile]dibromide (AHF-alt-PFN), the polymer typically obtained by the Suzuki type of polymerization reaction and shows good solubility in methanol. Bulk heterojunction polymer solar cells (BHJ-PSCs) fabricated by using water soluble conjugated polymer and positive (Cs+) and negative (F-, CO2-(3)) charge ions doping as an interfacial layer for poly(3-hexylthiophene):phenyl-C61 butyric acid methyl ester (P3HT:PCBM). We have achieved an enhancement of the short circuit density and power conversion efficiency in solar cell by introducing poly(AHF-alt-PFN) layer between the active layer and the cathode metal. The device with poly(AHF-alt-PRN) layer containing F-, CO2-(3) showed a short circuit current density more 1.3, 2.3 times higher than those of the device without poly(AHF-alt-PFN) + ion layer. We explain the better performance in solar cell with poly(AHF-alt-PFN) + ion layer was due not only to the increase of electron mobility in poly(AHF-alt-PFN) layer but also to the decrease of the electron barrier near cathode by the addition of the negative ions.
ABSTRACT
We have fabricated a polymer light-emitting diode (PLED) from the conventional blue-emitting polymer, polyfluorene (PFO), by constructing a multilayer structure with non-metal ion containing water soluble non-conjugated polymer, polyurethane with F- ion (PU:F-), on the top of the PFO. The device with PU:F- layer shows a maximum luminance of 5294 cd/m2 at an applied voltage of 10 V while the one without PU:F- layer shows only 4439 cd/m2 at the same applied voltage. We propose the improvement of device performance with PU:F- layer was due to not only an effective hole blocking at the polymer-polymer interface but also increase of electric field strength with anode after electro-stactic repulsion between electrons from the cathod and anions from the water soluble polymer layer. We will discuss the effect of multilayer polymer structure in PLED in terms of current/voltage characteristics, luminance, and quantum efficiency related with the applied bias.
