2, Center for Advancing Electronics Dresden (CFAED) and Department of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, , Germany
Indium Tin Oxide (ITO) has been widely used as transparent conductive electrode (TCE) in optoelectronics. However, it suffers from high production costs, dwindling supplies, limited chemical and mechanical stability. Therefore, seeking for an efficient alternative to ITO as TCE is of great significance. As first step we have investigated solution-processed transparent electrodes based on electrochemical exfoliated graphene (EG), characterized by remarkable properties (C/O ratio 17.9), high yield (78%) and low cost. Uniform and smooth electrodes have been obtained by spray-coating of a high-quality EG dispersion on both rigid and flexible substrates. Compared to previous reported solution processed graphene based TCEs, our EG electrodes show improved features (i.e. sheet resistance, Rs, as low as 0.18 kΩ sq–1). However, the organic solar cells (OSCs) based on these pristine EG electrodes exhibit power conversion efficiency (PCE) typically 40% lower than their ITO analogues. Hence, in order to enhance performances of the devices, keeping a feasible approach, we have developed a mixed-dimensional structure (1D-2D) using AgNWs and EG. Compared with pristine EG these hybrid TCEs exhibit a dramatic decrease of the sheet resistance Rs from 78 to 13.7 Ω sq-1 combined with an optical transparency of 89%. In addition the surface roughness (RMS) reduces from 16.4 to 4.6 nm and their mechanical and chemical stability is enhanced. The spray-coated hybrid AgNWs-EG TCEs have been successfully implemented in OSCs and polymer LEDs (PLEDs), which output remarkable efficiencies that are equivalent with their commercial ITO-based counterparts. To the best of our knowledge these are the first solution-processed transparent electrodes that match the performance of ITO based TCEs.
 S. Yang, A. G. Ricciardulli, S. Liu, R. Dong, M. R. Lohe, A. Becker, M. A. Squillaci, P. Samori, K. Mullen, X. Feng, Angew. Chem. Int. Ed. 2017, 56, 6669.
 A. G. Ricciardulli, S. Yang, X. Feng, P. W. M. Blom, ACS Appl. Mater. Interfaces 2017, 9, 25412.
 A. G. Ricciardulli, S. Yang, G. A. H. Wetzelaer, X. Feng, P. W. M. Blom, Submitted.