氧化鋅奈米棒與高規則度聚噻吩混摻太陽能電池研究

Abstract

本篇論文我們藉由氧化鋅奈米棒取代奈米粒子和共軛高分子聚噻吩(P3HT)混摻，減少電子跳躍傳遞的次數，增加短路電流，使光電轉換效率提高2.2倍。將濃縮的氧化鋅奈米粒子溶液再加熱，成功使氧化鋅奈米粒子自組裝排列成奈米棒，控制不同加熱時間可以合成不同長度的氧化鋅奈米棒。利用X光繞射儀鑑定氧化鋅奈米棒的晶體結構為wurtzite。選用兩種不同長度的氧化鋅奈米棒與聚噻吩混摻，討論不同混摻比例的光學性質的變化。隨著氧化鋅尺度縮小產生量子侷限效應，其UV光譜有藍位移的現象。當氧化鋅加入時除了會造成高分子上的能量轉移使PL下降，也會破壞原本P3HT的推疊規則度使PL上升，這兩個效應會互相競爭，影響著整體PL的強度，使我們無法從PL趨勢預估元件效率。再對氧化鋅混摻比例、膜厚與退火時間對元件效率造成的影響做一個比較，將所得到最佳化條件應用於不同型態的氧化鋅和P3HT混摻的系統，研究氧化鋅型態對元件效率的影響。以短氧化鋅奈米棒(直徑8nm、長度20~40nm)和P3HT混摻比例為0.9，最佳光電轉換效率可達0.5%。最後以原子力顯微鏡(AFM)和穿透式顯微鏡(TEM)分析混摻後的表面型態。

In this work, polymer based solar cell using blend zinc oxide nanorods and regioregular poly(3-hexylthiophene) can increase the power conversion efficiency by almost 220%. Application of nanorods can lead to an improved transport of electrons through the nanoparticle network because less electron hopping steps between individual nanoparticles are needed to bridge the distance to the collecting electrode. ZnO nanorods can be grown from the nanoparticles by heating a concentrated nanoparticle solution. The length of the rods can be tuned varying the heating time. We use high resolution X-ray diffractometer to determine the wurtzite structure of ZnO nanorods. In optical properties, Ultraviolet-visible Spectroscopy of regioregular P3HT blend with ZnO nanorods showed a blue shift in violet emission with a reduction in crystal size and revealed the quantum confinement effect. P3HT polymer chain stacking and conformational disorder caused by mixing with the ZnO nanorods. The photoluminescence intensity is unexpected because the photoluminescence of P3HT is known to be sensitive to the degree of chain order. The photovoltaic effect in devices, made by sandwiching the active ZnO rods：P3HT layer between charge-selective electrodes, has been studied as a function of the ZnO concentration and the thickness of the layer. We also investigated the different shape of the ZnO. Optimized devices have an estimated AM1.5 performance of 0.5%. Atomic force microscopy and transmission electron microscopy have been used to gain insight in the morphology of these blends.