單晶矽太陽能電池技術純熟，在市場上市佔率高，然而受限於矽的能隙為1.12 eV，使得其對於太陽光中波長在400 奈米以下及1200奈米以上的範圍之光電轉換效率很差。目前有不少人研究利用光捕捉（Light Harvesting）的方式捕捉波長在400奈米或者波長在1200奈米以上之光以供單晶矽太陽能電池利用，以提升其整體效率。

本研究將螢光高分子材料混摻EVA （ethylene vinyl acetate copolymer）太陽能電池封裝膜，使用螢光高分子材料不僅可以增加其在EVA中的相容性也可以抑制會造成螢光強度下降的quenching效應。而此螢光高分子材料經由螢光光譜儀證明其能將紫外光轉換成波長大於400奈米可供單晶矽太陽能電池利用之光。螢光高分子的合成是以含有-OH末端基之9-(hydroxymethyl) anthracene螢光分子當作起始劑與環聚酯(ε-caprolactone)以開環聚合的方式進行聚合反應得到螢光高分子9-APCL，並透過FTIR、NMR及GPC確認化學結構，以及藉由熱分析儀器TGA與DSC測得其熱性質。

9-APCL與EVA經由混料、抽料以及最後在90℃下壓成一約0.5 mm的膜，並經由SEM觀察膜的截面以探討其相容性。接著分別以純EVA與改質EVA膜當作封裝膜製成單晶矽太陽能電池模組，測試其在各波長下之外部量子效率(External Quantum Efficiency, EQE)，發現波長在400奈米以下的EQE皆有提升，最好的電池模組達到約50%。最後測試電池模組在太陽光模擬器的照射下所測得之I-V curve，經由計算得知效果最好的電池模組其發電效率比純EVA封裝之電池模組多0.8 %。

本研究結果顯示利用螢光高分子混摻EVA膜當作矽晶太陽能電池模組之封裝膜不僅不影響電池模組製程之程序且又能達到效率提升的效果。

Due to well-developed manufacturing process for monocrystalline silicon solar cell, monocrystalline silicon solar cell leads in the solar cell manufacturing market. However, because of the restriction of energy bandgap of Si (i.e., 1.12 eV), the monocrystalline silicon solar cell has much lower photo-sensitivity to ultraviolet light (λ<400 nm) and infrared light (λ>1200 nm) than visible light. Nowadays, lots of researches develop to utilize the method called light harvesting to enhance the efficiency of monocrystalline silicon solar cell by converting ultraviolet light or infrared light to the light which is more photo-sensitive to monocrystalline silicon solar cell.

In this study, we report on the use of a novel fluorescent polymer doped in the EVA (ethylene vinyl acetate copolymer) encapsulation layer of solar module for light harvesting. The utilization of fluorescent polymer not only can improve the miscibility in EVA matrix but suppress the quenching effect which would lower the fluorescent intensity. And this fluorescent polymer can absorb ultraviolet light, then emit fluorescent light which is more photo-sensitive to monocrystalline silicon solar cell proved by fluorescence spectrophotometer. The synthesis of fluorescent polymer, 9-APCL, was carried out through ring-opening polymerization (ROP) by taking the organic fluorescent molecules with mono-hydroxyl group: 9-(hydroxymethyl) anthracene as ROP initiator and ε-caprolactone as monomers. Moreover, the chemical structure and the thermal properties of 9-APCL were characterized by FTIR, NMR, GPC, TGA and DSC.

The blending of 9-APCL and EVA was prepared in a rotating one-screw extruder. And then the film with thickness approximate 0.5 mm was prepared via thermally pressing the blended pellet by a Laminator. In order to study the miscibility of 9-ACPL and EVA, the morphology was examined by scanning electron microscopy. Subsequently, we used both neat EVA and modified EVA respectively as encapsulant to make monocrystalline silicon solar modules. Finally the characterization of photovoltaic including External Quantum Efficiency (EQE) and I-V curve were measured. The best-performed solar module in this study shows an enhancement of approximate 50% in EQE for the wavelength from 300 to 400 nm, which results in 0.8% higher overall efficiency relatively to the solar module which encapsulated with neat EVA.

This study has shown that an enhancement in the performance of monocrystalline silicon solar modules can be achieved, without any modification to the well-established manufacturing process.
 

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