High-resolution imaging of electrochemical doping and dedoping processes in luminescent conjugated polymers

We report fluorescence imaging of extremely large planar polymer light-emitting electrochemical cells (LECs) with high spatial and temporal resolution. The type of cation used has been shown to strongly affect n-doping propagation. When left to relax, p doping undergoes significantly faster relaxation than n doping. Imaging also confirms that a p-n junction, rather than a p-i-n junction, is formed in fully turned on LECs, which suffer from heavy photoluminescence quenching throughout the polymer film. However, a p-i-n junction with a much less quenched “intrinsic” region can be formed by relaxing a p-n junction without bias, suggesting a simple approach for achieving more efficient LECs.