Figure 2.

The temporal evolution of the normalized forward electroluminescence spectrum of LECs with different active-layer thickness, as identified in the upper right corner. The arrows and colors indicate increasing time from 1–2 min (initial, blue line), over 5–60 min (transition, red line), to 180 min (steady-state, green line). The photoluminescence spectrum of a thin film of the conjugated-polymer emitter, Super Yellow, is included as the black dashed line for reference. The inset photographs show the corresponding forward emission color during steady-state operation.