Synergistic Roll‐to‐Roll Transfer and Doping of CVD‐Graphene Using Parylene for Ambient‐Stable and Ultra‐Lightweight Photovoltaics

Abstract

Large area graphene grown by chemical vapor deposition (CVD) has been the main focus of many researchers due to its vast areas of applications such as sensing or photovoltaics.Addressing the main challenges in transfer techniques such as Roll-to-Roll (R2R) process is a critical step for scaling up and commercialization of graphene. In this work, we employ a R2R transfer technique and improve the electrical properties of transferred graphene on flexible substrates using parylene as an interfacial layer. We deposit a layer of parylene on graphene/copper (Cu) foils grown by CVD and laminate them onto EVA/PET. Then, the samples are delaminated from the Cu using an electrochemical transfer process, resulting in flexible and conductive substrates with sheet resistance of below 300 Ω/sq, which is significantly better (4-fold) than the sample transferred by R2R without parylene (1200 Ω/sq). By scanning over different types of parylene (N, C, and D) here, we find that parylene C and D are better candidates than parylene N, given the higher conductivity measured on the as-transferred graphene samples. Our characterization results indicate that parylene C and D dope graphene due to the presence of chlorine atoms in their structure, resulting in higher carrier density and thus lower sheet resistance. Density functional theory (DFT) calculations reveal that the binding energy between parylene and graphene is stronger than that of EVA and graphene, which may lead to less tear in graphene during the R2R transfer. Finally, we fabricate organic solar cells (OSCs) on the ultrathin and flexible parylene/graphene substrates and achieve an ultra-lightweight device with a power conversion efficiency (PCE) of 5.86% comparable with PET/ITO ones, which has also a high power-per-weight of 6.46 W/g. In this study, we employ PV2000/PC 60 BM blend for the device fabrication, which does not require any encapsulation due to its superior air-stability.

Spectacular Oxygen Evolution Reaction Enhancement through Laser Processing of the Nickel‐Decorated Titania Nanotubes

“…Growing concerns for a natural environment drive innovation toward novel, clean energy sources, and storage devices. [ 1,2 ] Among them, cheap but efficient water‐splitting devices are being developed, and great hopes are being put into light‐enabled catalysts. The titania‐based electrode materials are especially looked at, because of their abundance, flexibility, and high stability within a wide pH range.…”

Mutually Reinforced Polymer–Graphene Bilayer Membranes for Energy‐Efficient Acoustic Transduction

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Monolayer Hexagonal Boron Nitride: An Efficient Electron Blocking Layer in Organic Photovoltaics

“…2D materials, especially graphene, have attracted many researchers in the field of solar cells due to their exciting optoelectronic properties 33–35 . Since the scaling trend in the photovoltaic (PV) technology is moving toward lighter and thinner devices, the atomically thin structure and great flexibility of 2D materials make them ideal candidates for the next generation of thin film PVs 36,37 . For instance, monolayer graphene has shown great potential to be used as top and bottom electrodes in the thin film solar cells 38–41 .…”