Photonically Cured Solution Deposited Hybrid Transparent Conducting Electrode Fabricated with Methods Scalable to Web Speeds > 10 m/min

Transparent conducting electrodes are used in many applications such as LEDs, displays, and solar cells. Ideal transparent conducting electrodes have low sheet resistance, high transmittance, and low surface roughness. This work demonstrates a roll-to-roll (R2R) compatible process to fabricate hybrid transparent conducting electrodes on PET. Roll-to-roll manufacturing at a commercial scale requires flexible substrates that can be conveyed at processing speeds > 10 m/min. Solution deposition via blade coating, gravure, or flexographic printing can be performed at a high speed with low capex cost. However, thermal annealing is too slow and can damage PET; thus, we adapt photonic curing for post-deposition processing. Photonic curing uses a xenon flash lamp to deliver micro-to-millisecond light pulses onto the sample and heat specific films via light absorption. High temperatures can be achieved in the film processed using photonic curing with the PET substrate staying at low temperatures because the short light pulse can be of high intensity and low energy. This work applies photonic curing to make hybrid transparent conducting electrodes that consist of a multi-scale Ag network of metal bus lines (MBLs) and nanowires (AgNWs), overcoated with indium zinc oxide (IZO) on PET. We achieved an average transmittance > 80%, sheet resistance < 15 ohms/sq, and surface roughness < 5 nm. The AgNWs and IZO are blade coated at a 1.5 m/min speed and photonically cured at speeds > 10 m/min. TEM cross sections and SEM images show IZO planarizing MBLs and AgNWs.^[1] Bending tests are performed to show the material can be conveyed over 2” diameter rollers. XPS analysis shows metal oxide conversion after photonic curing. The process is then adapted to gravure/flexographic printing at speeds up to 60 m/min to further demonstrate scalability. Perovskite solar cells are fabricated on top of these hybrid TCEs and benchmarked against commercial TCEs.