Luminescent and photovoltaic properties of poly(9,9-dioctylfluorene-co-bithiophene) in organic electronic devices

We studied the luminescent and photovoltaic properties of poly(9,9-dioctylfluorene-co-bithiophene)(F8T2) based on ITO/PEDOT:PSS/F8T2/Bphen/LiF(0 or 1 nm)/Al and ITO/PEDOT:PSS/F8T2:PCBM/Bphen/Al.A stable and bright yellow emission was obtained from polymer F8T2,and the electroluminescence power reached 45 ?W at a 15 V driving voltage.Polymer F8T2 shows a broad absorption band from 400 to 500 nm,and has a shorter absorption edge at about 560 nm compared to that of the typical electron donor P3HT(650 nm).The photoluminescence quenching of F8T2 occurs with only a small fraction of blended PCBM due to the effective exciton dissociation at the interface between F8T2 and PCBM.Polymer solar cells(PSCs) using F8T2:PCBM as the active layer show a low power conversion efficiency(PCE) of 0.10% with an open circuit voltage(Voc) of 0.91 V and short circuit current density(Jsc) of 0.23 mA/cm2.The PSCs using F8T2:P3HT:PCBM as the active layer have a Voc of 0.85 V and Jsc of 3.02 mA/cm2,improving the PCE by about 0.90%.We attribute the improved cell performance to the higher number of photons harvested by P3HT molecules.

We studied the luminescent and photovoltaic properties of poly（9,9-dioctylfluorene-co-bithiophene） （F8T2） based on ITO/ PEDOT： PSS/F8T2/Bphen/LiF（0 or 1 nm）/A1 and ITO/PEDOT： PSS/F8T2 ： PCBM/Bphen/A1. A stable and bright yellow emis- sion was obtained from polymer F8T2, and the electroluminescence power reached 45 laW at a 15 V driving voltage. Polymer F8T2 shows a broad absorption band from 400 to 500 nm, and has a shorter absorption edge at about 560 nm compared to that of the typical electron donor P3HT （650 nm）. The photoluminescence quenching of F8T2 occurs with only a small fraction of blended PCBM due to the effective exciton dissociation at the interface between F8T2 and PCBM. Polymer solar cells （PSCs） using F8T2 ： PCBM as the active layer show a low power conversion efficiency （PCE） of 0.10% with an open circuit voltage （Voc） of 0.91 V and short circuit current density （Jsc） of 0.23 mA/cm2. The PSCs using F8T2：P3HT：PCBM as the active layer have a Voc of 0.85 V and Jsc of 3.02 mA/cm2, improving the PCE by about 0.90%. We attribute the improved cell performance to the higher number of photons harvested by P3HT molecules.