Switchable polarity in polymer solar cells using conjugated polyelectrolyte

We report polarity-switchable polymer solar cells that use poly [(9,9-bis((6′-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis(2-(2-(2-methoxy-ethoxy)ethoxy)ethyl)-9-fluorene))dibromide polyelectrolyte (WPF-6-oxy-F). By introducing WPF-6-oxy-F as a polarity-controlling layer, we selectively achieved polarity switching in the device operation. When we deposited the WPF-6-oxy-F film on the top of an active polymer layer, the device operated conventionally; holes moved to the transparent indium tin oxide (ITO) electrode. However, the device showed switched polarity when we changed the position of insertion of the WPF-6-oxy-F film to the top of the transparent ITO electrode. Then, the electrons moved to the transparent ITO electrode, leading to an inverted device.