Sunlight-activated Graphene-heterostructure Transparent Cathodes：Enabling High-performance n-graphene/p-Si Schottky Junction Photovoltaics
Date Issued
2015
Date
2015
Author(s)
Lee, Wei-Chen
Abstract
Graphene, which consists of a single atom-thick layer of carbon, has a lot of attracting properties such as tunable work function, high transparency and high carrier mobility etc. All these properties make graphene be a promising material to replacing widely-used ITO as transparent conducting electrode. However, compared to well-developed graphene-based anodes, fabricating a stable graphene-based cathode is more difficult because n-type dopants for graphene have limited thermal and chemical stabilities and are also sensitive to the influence of ambient environment. In the first part of this thesis, we developed a novel “sunlight-activated” graphene-heterostructure transparent electrode. Besides, TiOx was found to be an effective n-type dopant for graphene by surface charge transfer process. With only costing a small amount of ultraviolet, TiOx will photo-generates charges under illumination then are transferred toward graphene and further doped it. This photoactive TiOx/graphene heterostructure transparent electrode exhibits excellent tunable electrical properties and is appropriate to fabricate an n-graphene/p-silicon Schottky junction solar cell, even achieving a record-high power efficiency of graphene/p-silicon structure. In the second part, we aim to improve the performance of device in the first part. With more suitable anti-reflective layers, back contact electrodes, and surface passivation, we demonstrate a “trap-free” photoactive n-graphene/p-Si Schottky solar cell with higher short circuit current and open circuit voltage. This device is also an ideal candidate for future derivatives of tandem cells.
Subjects
Chemical vapor deposition graphene
Schottky solar cells
graphene cathodes
photoactive doping
graphene heterostructure
SDGs
Type
thesis
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