Continuous, Highly Flexible, and Transparent Graphene Films by Chemical Vapor Deposition for Organic Photovoltaics

Abstract

We report the implementation of continuous, highly flexible, and transparent graphene films obtained by chemical vapor deposition (CVD) as transparent conductive electrodes (TCE) in organic photovoltaic cells. Graphene films were synthesized by CVD, transferred to transparent substrates, and evaluated in organic solar cell heterojunctions (TCE/poly-3,4-ethylenedioxythiophene:poly styrenesulfonate (PEDOT:PSS)/copper phthalocyanine/fullerene/bathocuproine/aluminum). Key to our success is the continuous nature of the CVD graphene films, which led to minimal surface roughness ( approximately 0.9 nm) and offered sheet resistance down to 230 Omega/sq (at 72% transparency), much lower than stacked graphene flakes at similar transparency. In addition, solar cells with CVD graphene and indium tin oxide (ITO) electrodes were fabricated side-by-side on flexible polyethylene terephthalate (PET) substrates and were confirmed to offer comparable performance, with power conversion efficiencies (eta) of 1.18 and 1.27%, respectively. Furthermore, CVD graphene solar cells demonstrated outstanding capability to operate under bending conditions up to 138 degrees , whereas the ITO-based devices displayed cracks and irreversible failure under bending of 60 degrees . Our work indicates the great potential of CVD graphene films for flexible photovoltaic applications.

Self‐Assembled Graphene‐Based Architectures and Their Applications

“…The AuCN nanowires could align themselves along the zigzag lattice direction of graphene, which originated from the interaction with the gold atom and the lattice match suggested by the first‐principles calculations. Dangling bonds of damaged graphene,132, 133 vapor‐phase deposition at high temperature,134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148 and intermediate seed materials132, 148, 149, 150 have been used to produce the hybrid of pristine graphene/inorganic nanostructure; however, the formed inorganic nanostructures were randomly oriented or poorly aligned on pristine graphene. This work paves a new way for precisely assembling inorganic nanomaterials on pristine graphene 93, 135, 136, 137, 138, 139…”

“…The resulting TiO 2 /GAs composite showed high specific capacity and high recyclability of photocatalytic activity for methyl orange pollutant when used for photocatalysis and Li‐ion battery. Other metal or metal oxides or hydroxides (e.g., TiO 2 , SnO 2 , NiOH, and MnO 2 ) have also been assembled on graphene, forming hybrids with well‐controlled nanostructures by using a similar strategy 142, 143, 144, 145, 146, 147…”

Color-stable, ITO-free white organic light-emitting diodes with enhanced efficiency using solution-processed transparent electrodes and optical outcoupling layers

“…Furthermore, the energy level mismatch between the work function of ITO and the highest occupied molecular orbital (HOMO) of typical organic hole transport layers often hinders hole injection and formation of ohmic contacts. [1][2][3][4][5] Accordingly, alternative transparent electrodes for the replacement of ITO, such as carbon nanotubes, [6] graphene, [7] thin metals, [8,9] metal grids, [10] metal nanowires [11] and conducting polymers [12][13][14] have been widely investigated.…”

Comparison Characteristic of Large Area Graphene Films Grown by Chemical Vapor Deposition with Nano-Graphite Structures

“…It has exceptional carrier transport properties which makes it a promising material for future nanoelectronics [4]. Besides graphene's high optical transmittance and conductivity it is also being considered as transparent electrode for flexible transparent displays and printable electronics [5]- [7]. To realize these potential applications, it is essential to synthesize high-quality and large-area graphene films.…”