Boosting Photon Harvesting in Organic Solar Cells with Highly Oriented Molecular Crystals via Graphene鈥揙rganic Heterointerface
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- 作者：Sae Byeok Jo ; Hyun Ho Kim ; Hansol Lee ; Boseok Kang ; Seongkyu Lee ; Myungsun Sim ; Min Kim ; Wi Hyoung Lee ; Kilwon Cho
- 刊名：ACS Nano
- 出版年：2015
- 出版时间：August 25, 2015
- 年：2015
- 卷：9
- 期：8
- 页码：8206-8219
- 全文大小：926K
- ISSN：1936-086X
文摘
Photon harvesting in organic solar cells is highly dependent on the anisotropic nature of the optoelectronic properties of photoactive materials. Here, we demonstrate an efficient approach to dramatically enhance photon harvesting in planar heterojunction solar cells by using a graphene鈥搊rganic heterointerface. A large area, residue-free monolayer graphene is inserted at anode interface to serve as an atomically thin epitaxial template for growing highly orientated pentacene crystals with lying-down orientation. This anisotropic orientation enhances the overall optoelectronic properties, including light absorption, charge carrier lifetime, interfacial energetics, and especially the exciton diffusion length. Spectroscopic and crystallographic analysis reveal that the lying-down orientation persists until a thickness of 110 nm, which, along with increased exciton diffusion length up to nearly 100 nm, allows the device optimum thickness to be doubled to yield significantly enhanced light absorption within the photoactive layers. The resultant photovoltaic performance shows simultaneous increment in Voc, Jsc, and FF, and consequently a 5 times increment in the maximum power conversion efficiency than the equivalent devices without a graphene layer. The present findings indicate that controlling organic鈥揼raphene heterointerface could provide a design strategy of organic solar cell architecture for boosting photon harvesting.