有機上轉換型光伏元件

Abstract

利用980奈米波長的雷射照射一般的高分子光伏元件，我們已發現可以看到明顯的 光伏效應，由於高分子材料在650 nm之後並沒明顯的吸收，我們認為此現象可能是高分 子元件的光上轉換過程所引起的，此發現將帶給有機太陽能電池領域一個新的衝擊。「有 機上轉換型光伏元件」之研究計劃將系統性地研究此上轉換的現象與機制及對高分子元 件特性的影響。我們首先除了元件製作參數的最佳化與基本的特性分析外，也將藉由不 同的光譜技術系統性的研究電荷轉移激子的物理特性，同時也會使用具有不同能階的材 料製作元件，並檢視元件特性與材料能階之間的關係，藉此得知電荷轉移激子在上轉換 機制可能扮演的角色。而我們也將探討另一個可能的非線性機制，將仔細研究元件是否 呈現出任何的非線性現象，高分子薄膜型態也會以原子力顯微鏡等方式研究，用以幫助 機制的理解，也將發展新的元件結構用以降低長波長光子在元件中的散失。最後我們也 將探索此元件在生醫光電領域(如無線奈米生物機械人)應用的可能性。在計畫的第二年 度，我們將以數種方式改善元件的效能。我們將以不同的結構置入上轉換磷光物質於元 件中，並研究陰極金屬反射率的影響與可能的固態溶媒效應，也將進一步分析元件的內 部光電場的分佈，並經電場的最佳化增加元件的光吸收，也擬藉由加入光學間隙層與金 屬奈米粒子所誘導的表面電漿效應改善光子的吸收效率。預計成功執行本計劃後上轉換 高分子光伏元件的效率將被大幅改善，並將對有機太陽能電池領域有所貢獻。

We have found pronounced photovoltaic effect in polymer solar cells upon the illumination of a 980-nm laser. Because the organic materials used in the device cannot absorb photons with wavelength longer than 650 nm, we attributed such effect to up-conversion process in the photovoltaic device. The initial result of up-conversion photovoltaic effect may bring a new concept to the research area of organic solar cells. The “study of up-conversion organic photovoltaic devices” research project will aim to systematically investigate up-conversion mechanism in organic materials and its effects on the device performance of photovoltaic devices. In the first year, the device performance will be firstly studied by optimizing the fabrication processes. The possible origins of the up-conversion effect will be studied systematically through the investigation of the charge-transfer states. Materials with different energy levels will be used to fabricate the devices; their electrical performance will be correlated to the physical properties of the charge-transfer excitons. The other possible mechanism is due to the nonlinear phenomena of organic materials. The device characteristics will be carefully studied to see if we could observe any nonlinear effect. The morphology of the polymer blends will be also examined. New device architecture will be further used to minimize the energy losses in the near-Infrared wavelength regime. Finally, possible application of these devices on wireless biological nanorobots will be examined. In the second year, the device performance will be further improved by several approaches. The up-conversion phosphors will be incorporated into the device. The effect of the reflection of the metal cathodes will be studied. Possible solid-state solvation effect will be investigated. For improving the photon absorption efficiency, optical electric field in the device structure will be analyzed and optical spacers will be inserted into the device. Additionally, surface plasmonic effect induced by the introduction of metal nanoparticles will be also employed. The device efficiency of the up-conversion solar cells are anticipated to be improved significantly after the success of this project. The results of this project will contribute significantly to the field of organic solar cells.