Nanoparticle scattering layer based on polymer-metal oxide composite is successfully introduced to enhance the light extraction efficiency of organic light emitting diodes (OLEDs). We find that the density and the distribution of nanoparticles is the key factor to maximize the light extraction efficiency of pristine OLEDs by out-coupling the unusable light with the scattering film. In our experiment, 71 wt% of Al(2)O(3) mixed with polymer matrix shows the increase of light extraction efficiency of 40%. This method is expected to play a critical role to create the low-power OLED application such as OLED lightings with simple fabrication process and low cost.
Understanding
the effects of the chemical structures of donor polymers on the photovoltaic
properties of their corresponding organic photovoltaic (OPV) devices
under various light-intensity conditions is important for improving
the performance of these devices. We synthesized a series of copolymers
based on poly[(2,6-(4,8-bis(5-(2-thioethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))]
(PBDB-TS) and studied the effects of chlorine substitution of its
thiophene-substituted benzodithiophene (BDT-Th) unit on its photovoltaic
properties. Chlorination of the polymer resulted in a bulk heterojunction
(BHJ) morphology optimized for efficient charge transport with suppressed
leakage current and an increased open-circuit voltage of the OPV device;
this optimization led to a remarkable enhancement of the OPV device’s
power conversion efficiency (PCE) not only under the condition of
1 sun illumination but also under a low light intensity mimicking
indoor light; the PCE increased from 8.7% for PBDB-TS to ∼13%
for the chlorinated polymers, PBDB-TS-3Cl, and PBDB-TS-4Cl under the
1 sun illumination condition and from 5.3% for PBDB-TS to 21.7% for
PBDB-TS-4Cl under 500 lx fluorescence illuminance. Interestingly,
although the OPV PCEs under 1 sun illumination were independent of
the position of chlorine substitution onto the polymer, PBDB-TS-4Cl
exhibited better performance under simulated indoor light than its
derivative PBDB-TS-3Cl. Our results demonstrate that efficient light
absorption and charge-carrier generation play key roles in achieving
high OPV efficiency under low-light-intensity conditions.
We report two newly synthesized naphthalene diimide (NDI)-based conjugated polymers, poly[(E)-2,7-bis(2-decyltetradecyl)benzo [lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-vinylene-thiophene-vinylene] (PNDI-VTV) and poly[(E)-2,7-bis(2-decyltetradecyl)benzo [lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-vinylene-selenophene-vinylene] (PNDI-VSV) with different donor units as electron-transporting organic semiconductors for organic fieldeffect transistors (OFETs). Furthermore, we study the effect of vinylene position on electron transport in the NDI polymers by using two similar polymers but with thiophene-vinylene-thiophene (PNDI-TVT) instead of vinylene-thiophene-vinylene or selenophene-vinylene-selenophene (PNDI-SVS) instead of vinyleneselenophene-vinylene. By incorporating vinylene between thiophene (or selenophene) units, the resulting NDI-based polymers PNDI-VTV and PNDI-VSV show larger backbone planarity than PNDI-TVT and PNDI-SVS. The polymers with a shorter acceptor monomer unit (PNDI-VTV and PNDI-VSV) show a strong face-on orientation, whereas those with a longer monomer unit (PNDI-TVT and SVS) exhibit a mixed face-on and edge-on orientation by two-dimensional grazing incidence X-ray diffraction. Optimized PNDI-VTV and PNDI-VSV OFETs exhibit electron mobilities of 0.043 and 0.7 cm 2 /(V•s), which is quite lower than those of PNDI-TVT and PNDI-SVS. In addition, the activation energies for electron transport of PNDI-VTV and PNDI-VSV were larger than those of PNDI-TVT and PNDI-SVS. Overall, this research provides the insight that the molecular alignment on the substrate can be controlled by the sequence of rigid acceptor monomer molecules for improving the electron transport of NDI polymers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.