The bell-shaped response functions of the first twelve species (left panel) and the U-shaped response functions of the next eight species (right panel).

<p>The bell-shaped response functions of the first twelve species (left panel) and the U-shaped response functions of the next eight species (right panel).</p

Ordination diagram of the BECOA analysis of a subset of the Antarctic lake data, with penalisation parameter <i>δ</i> being -1.7 for the first dimension and = 0.7 for the second dimension.

<p>Numbers represent lakes. The points represent the species optima, with symbols indicating the shape of the corresponding species response function when <i>δ</i> = 0: p1, U-shaped in 1st and 2nd dimension; p2, bell-shaped in 1st dimension; p3, bell-shaped in 2nd dimension; p4, bell-shaped in 1st and 2nd dimension. Species labels are added.</p

Results for the case study in the second dimension.

<p>Estimated coefficients of environmental gradient (a) and the average number of bell-shaped response functions (b) as a function of penalty parameter <i>δ</i>. Relative changes of average LLR (c) and average SSE (d) as a function of penalty parameter <i>δ</i>.</p

Ordination diagram of the BECOA analysis of the Antarctic lake data, with penalisation parameter <i>δ</i> being -1.7 for the first dimension and = 0.7 for the second dimension.

<p>Numbers represent lakes. The points represent the species optima, with symbols indicating the shape of the corresponding species response function when <i>δ</i> = 0: p1, U-shaped in 1st and 2nd dimension; p2, bell-shaped in 1st dimension; p3, bell-shaped in 2nd dimension; p4, bell-shaped in 1st and 2nd dimension.</p

Influence of the Guest on Aggregation of the Host by Exciton–Polaron Interactions and Its Effects on the Stability of Phosphorescent Organic Light-Emitting Devices

The root causes of the differences in electroluminescence stability among phosphorescent organic light-emitting devices (PHOLEDs) utilizing different emitter guests are studied. The results show that the host material plays a more influential role in limiting device stability in comparison to the guest. During the operation of a PHOLED, the host undergoes aggregation as a result of interactions between the excitons and positive polarons. The rate of this aggregation is found to be the limiting factor for device lifetime and is influenced by the choice of the guest material and its concentration. Finally, it is shown that phase segregation between the host and the guest is an important aspect of the aggregation process. As a result of this segregation, energy transfer from the host to the guest becomes increasingly less efficient, resulting in the observed gradual loss in electroluminescence efficiency in the devices over time. The findings explain why PHOLEDs utilizing different guest materials but otherwise identical material systems can have significantly different lifetimes and provide an answer to a long-lasting question in the field

Results of the simulation study.

<p>(a) the averages of the estimated environmental gradients as a function of the penalty parameter <i>δ</i>; the intervals shown on top are proportional to the total variance of the estimates. (b) the average number of bell-shaped response functions as a function of the penalty parameter <i>δ</i>. (c) for each of the 20 species the graph shows the evolution of the ’s as <i>δ</i> changes. (d) for each of the 20 species the graph shows the evolution of the Sum of Squared Errors (SSE) of the fits of the response functions for the penalty parameter moving from <i>δ</i> = 0 (symbol: +) to <i>δ</i> = −1 (symbol: O); the dots represent the intermediate results with larger dots representing smaller penalisation.</p

The relative changes of average LLR (left) and average SSE (right) as a function of the penalty parameter <i>δ</i>.

<p>The relative changes of average LLR (left) and average SSE (right) as a function of the penalty parameter <i>δ</i>.</p

The parameters used for the U-shaped response functions for species <i>k</i> = 13, …, 20. For all species, the scaling parameters <i>s</i>_<i>k</i> are set to so as to make the maxima comparable.

<p>The parameters used for the U-shaped response functions for species <i>k</i> = 13, …, 20. For all species, the scaling parameters <i>s</i>_<i>k</i> are set to so as to make the maxima comparable.</p

The parameters used for the bell-shaped response functions for species <i>k</i> = 1, …, 12.

<p>For all species, the scaling parameters <i>s</i>_<i>k</i> are set to (<i>η</i>_<i>k</i>+<i>ζ</i>_<i>k</i>) so as to make the maxima comparable.</p

Results for the case study in the first dimension.

<p>Estimated coefficients of environmental gradient (a) and the average number of bell-shaped response functions (b) as a function of penalty parameter <i>δ</i>. Relative changes of average LLR (c) and average SSE (d) as a function of penalty parameter <i>δ</i>.</p