A Transparent Electrode Based on Solution-Processed ZnO for Organic Optoelectronic Devices

Achieving high-efficiency indium tin oxide (ITO)-free organic optoelectronic devices requires the development of high-conductivity and high-transparency materials for being used as the front electrode. Herein, sol-gel-grown zinc oxide (ZnO) films with high conductivity (460 S cm(-1)) and low optical absorption losses in both visible and near-infrared (NIR) spectral regions are realized utilizing the persistent photoinduced doping effect. The origin of the increased conductivity after photo-doping is ascribed to selective trapping of photogenerated holes by oxygen vacancies at the surface of the ZnO film. Then, the conductivity of the sol-gel-grown ZnO is further increased by stacking the ZnO using a newly developed sequential deposition strategy. Finally, the stacked ZnO is used as the cathode to construct ITO-free organic solar cells, photodetectors, and light emitting diodes: The devices based on ZnO outperform those based on ITO, owing to the reduced surface recombination losses at the cathode/active layer interface, and the reduced parasitic absorption losses in the electrodes of the ZnO based devices. A highly conductive and transparent electrode is essential to achieving a high efficiency in indium tin oxide-free optoelectronic devices. Here, the authors strategically prepare sol-gel-grown zinc oxide films based on photoinduced doping effect and demonstrate enhanced performance of devices.

Automated summary

This study focuses on the key issue of high-efficiency indium tin oxide-free organic optoelectronic devices. It achieves high conductivity and low optical absorption losses in zinc oxide films through the photoinduced doping effect, and further improves the conductivity by using a stacking strategy.