表面科学

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太陽光発電が牽引する日本の再生可能エネルギー

瀬川浩司

2014 年 35 巻 11 号 p. 594
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.594

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特集：有機系太陽電池の最先端

有機系太陽電池の光電変換効率の理論限界

関和彦

原稿種別: 総合報告
2014 年 35 巻 11 号 p. 595-602
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.595

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Organic and inorganic photovoltaic cells can be classified as excitonic solar cells and pn-junction solar cells, respectively. In this article, a fundamental difference in the operational mechanism between them is explained. The detailed balance limit of power conversion efficiency (PCE) was already established for pn-junction solar cells by Shockley and Queisser. Recent attempts to obtain theoretical limits of PCE for excitonic solar cells are reviewed.

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新規フラーレン系材料によるバルクヘテロジャンクション有機太陽電池の効率向上

松尾豊

原稿種別: 研究紹介
2014 年 35 巻 11 号 p. 603-608
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.603

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This article focuses on the synthesis, design concepts and photovoltaic performance of fullerene-based electron acceptors used in solution processed bulk heterojunction organic solar cells. Excellent fullerene acceptors such as 56π-electron conjugated dihydromethanofullerene derivatives, ICBA, methano-indene-fullerenes, mix-PCBM are introduced from a synthetic chemistry viewpoint in addition to fullerene chemistry background being offered, which should benefit a wide range of organic solar cell research.

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有機太陽電池の外部量子効率と電子供与体膜の結晶性・分子配向性

尾上順

原稿種別: 研究紹介
2014 年 35 巻 11 号 p. 609-614
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.609

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Organic solar cells have been intensively investigated as next-generation solar cells, because of their fascinating advantages of lightweight, low fabrication cost, resource-free, and flexibility. However, the fundamental aspects for improving the energy conversion efficiency (η) have been unclear satisfactorily. In this review, I report on the effects of molecular crystallinity/orientation of a donor film on the external quantum efficiency, which is one of the most important factors to determine the η, of Zinc-porphyrin/C₆₀ hetero-junction solar cells.

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電子-正孔対のフリーキャリアへの分離機構の理論研究

田村宏之

原稿種別: 研究紹介
2014 年 35 巻 11 号 p. 615-620
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.615

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This article introduces our recent studies on charge separation mechanism in organic solar cells. One of important questions on organic solar cells is how free electrons and holes are generated overcoming the Coulomb attraction at donor-acceptor interfaces. We carried out a combined electronic structure and quantum dynamical analysis that captures the elementary events from the exciton dissociation to the free carrier generation at polymer/fullerene donor-acceptor heterojunctions. Our calculations show that experimentally observed efficient charge separations can be explained by a combination of two effects: First, the delocalization of charges which substantially reduces the Coulomb barrier, and second, the vibronically hot nature of the charge transfer state which promotes charge dissociation beyond the barrier.

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有機太陽電池界面の長距離電子的相互作用：時間分解電子スピン共鳴法による電子状態解析

小堀康博, 三浦拓

原稿種別: 研究紹介
2014 年 35 巻 11 号 p. 621-626
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.621

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Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has been utilized at T = 77 K to characterize geometries and electronic couplings (V_CR) of transient charge-separated (CS) states in photoactive layers in organic thin film solar cells fabricated by spin-coating of mixed solutions of polyalkylthiophenes (RR-P3AT) and [6, 6]-C₆₁-butyric acid methyl ester (PCBM). Electron-hole distance of the interfacial transient CS states has been revealed to be modulated by alkyl side-chain number in P3AT. This result is explained by a coupling of a hole dissociation to polymer librations by the side-chains. From an exponential decay of V_CR with respect to the CS distance, an attenuation factor (β_e) of the decay has been determined to be β_e＝0.2 Å⁻¹. Such a long-range tunneling feature is explained by generations of shallowly trapped, delocalized electron-hole pairs by the dissociations of the hole toward π-stacking directions at the organic photovoltaic interface.

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広帯域増感色素と有機金属ハライドペロブスカイトを用いた高効率有機系タンデム太陽電池

木下卓巳, 瀬川浩司

原稿種別: 研究紹介
2014 年 35 巻 11 号 p. 627-632
発行日: 2014/11/10
公開日: 2014/11/22

DOIhttps://doi.org/10.1380/jsssj.35.627

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Tandem-type solar cell is a multiple-layered solar cell to decrease thermal- and optical-energy losses. However, typical organic photovoltaics has been difficult to apply tandem photovoltaics because of the lack of organic photovoltaic cells with high open-circuit voltage (V_OC) and/or near-infrared (NIR) photoelectric conversion. In this study, we constructed tandem-type organic photovoltaics using high V_OC organometal halide perovskite solar cell and NIR dye-sensitized solar cell. Consequently, over 16% power conversion efficiency which is highest record among tandem-type organic photovoltaics has been accomplished.

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