兩步驟官能基置換方式之硒化鉛量子點之特性分析與光伏元件應用

Abstract

本篇論文利用溶液相合成法，合成出不同第一激發吸收峰之硒化鉛量子點。探討硒化鉛量子點大小及其經過兩步驟官能基置換過程的吸收峰位置、薄膜表面形貌的改變及不同主動層厚度之太陽能電池光電轉換效率、外部量子效率與長時間持續照射下之元件壽命。 實驗中觀察發現當量子點粒徑越大時，其第一激發吸收峰波長越長；將不同粒徑大小之量子點量測元件電性，粒徑較小的硒化鉛量子點之開放電壓較大，且光電轉換效率較佳。使用正丁胺進行溶液相官能基置換的量子點旋轉塗佈在銦錫氧化物玻璃（ITO）/PEDOT:PSS上，會使薄膜表面形貌平整，再對此薄膜使用1,2-ethanedithiol溶液進行薄膜化學處理，表面會有些許裂縫產生。實驗中接連使用正丁胺進行溶液相官能基置換及1,2-ethanedithiol溶液進行薄膜化學處理可以有效去除大量油酸，且利用多層的主動層設計可以有效填補1,2-ethanedithiol處理過程中所產生的裂縫，並達到硒化鉛量子點應用在太陽能電池上的最佳厚度約95奈米。將所設計之最佳化元件結構及參數進行外部量子效率量測可以發現，此元件在可見光到紅外光波段皆有響應。因此，將其在太陽光AM 1.5G及紅外光波長830 奈米光源的照射下，量測其光電轉換效率分別為2.14％及2.93％。

In this work, we use solution-synthesis method to fabricate oleate-capped PbSe quantum dots (QDs) and investigate the first absorption peak, particle size, morphology of PbSe QDs and the PbSe QDs films treated with butylamine and 1,2-ethanedithiol (EDT). The above conditions and different thickness of the active layer are discussed by the current density–voltage( I-V) measurement. We observe that the increase of the PbSe QDs size results in the longer first absorption peak wavelength. However, the increase in open-circuit voltages upon decreasing the size of PbSe QD lets the device get a better photovoltaic performance. Butylamine and EDT ligand-exchange process remove the oleic acid on the surface of PbSe QDs and smooth the QDs film surface. Although there are some cracks on the film surface after the use of EDT treatment, the cracks can be filled effectively by the use of multilayer of PbSe QDs film and get the optimal thickness of ca. 95nm of PbSe QDs active layer. Moreover, we measured the External Quantum Efficiency (EQE) for the best PbSe QDs device. The EQE curve presents the photocurrent responses in the either infrared or visible range. Therefore, we get the power conversion efficiencies of 2.14％ and 2.93％ of the PbSe QDs device which was illuminated under solar AM 1.5G and monochromatic light 830 nm, respectively.