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Graphene shows great potential for flexible optoelectronic devices owing to its unique 2D structure and excellent electronic, optical, and mechanical properties. Chemical vapor deposition (CVD) is the most promising method for fabricating large‐area and high‐quality graphene films at an acceptable cost; therefore enormous efforts have been attempted to investigate the flexible optoelectronic devices based on CVD‐grown graphene. Here, recent advances and significant development of CVD‐grown graphene towards flexible optoelectronics including photodetectors, organic solar cells, and light‐emitting diodes are reviewed. Insight into the challenges of improvement of optoelectronic properties, work function tuning, as well as interfacial control of CVD‐grown graphene for high‐performance devices is provided. In particular, the availability to fabricate large‐area devices on the flexible substrates is discussed, which is crucial to drive the practical use of CVD‐grown graphene for future wearable optoelectronics. [ABSTRACT FROM AUTHOR]

Ambient solution-processed conductive materials with a sufficient low work function are essential to facilitate electron injection in electronic and optoelectronic devices but are challenging. Here, we design an electrically conducting and ambient-stable polymer electrolyte with an ultralow work function down to 2.2 eV, which arises from heavy n-doping of dissolved salts to polymer matrix. Such materials can be solution processed into uniform and smooth films on various conductors including graphene, conductive metal oxides, conducting polymers and metals to substantially improve their electron injection, enabling high-performance blue light-emitting diodes and transparent light-emitting diodes. This work provides a universal strategy to design a wide range of stable charge injection materials with tunable work function. As an example, we also synthesize a high-work-function polymer electrolyte material for high-performance solar cells. Ambient-stable solution-processed conductive materials with a low work function are essential to facilitate electron injection. Here, the authors design and synthesise polymer electrolyte with work function down to 2.2 eV for applications in high-performance light-emitting diodes and solar cells. [ABSTRACT FROM AUTHOR]

Large‐area fabrication and stacking of various nanometer‐thick functional layers from solutions is essentially important for the construction of flexible thin‐film optoelectronic devices, but very challenging. The existing fabrication methods suffer from either non‐uniformity caused by the coffee‐ring effect or serious solution waste (excess of 90% for spin coating), and are hard to scale up and create stacks. Here, it is shown that centrifugal casting is a universal, scalable, and efficient method to fabricate uniform nanometer‐thick films and their stacks of various materials. The coffee‐ring effect is effectively suppressed, the solution utilization ratio is higher than ≈61%, and the films/stacks show a smooth surface/high‐quality interface. Using this method, flexible quantum dot light‐emitting diode displays with uniform luminance in a large lighting area of ≈115 cm2 that have not been achieved even on rigid substrates by the existing methods, are realized. This efficient and low‐cost solution processing method paves a way for large‐area fabrication of various flexible thin‐film optoelectronic devices. [ABSTRACT FROM AUTHOR]