| 摘要: | 本研究合成不同形貌的硒化鎘(CdSe)量子點以應用於有機光伏太陽能電池(OPV)元件中主動層的施體(donor)。利用不同界面活性劑-三正辛基氧膦(TOPO)/正己基磷酸(HPA)、十六胺(HDA)/HPA以及油胺(OA)/十八烷烯(ODE)以合成CdSe奈米晶。此外，在閃鋅礦CdSe晶種上長出纖鋅礦分支的晶種成長法亦用以製備四足狀形貌的CdSe奈米晶。之後將CdSe奈米晶與聚(3-己烷基?吩) (P3HT)和富勒烯衍生物(PCBM)混合使其成為OPV元件中之主動層。所製備CdSe奈米晶的形貌、結構、表面化學狀態、光學性質以及OPV元件的效率量測則由穿透式電子顯微鏡(TEM)、X光繞射分析(XRD)、光電子能譜儀(XPS)、感應耦合電漿原子發射光譜分析儀(ICP-AES)、紫外可見光吸收光譜儀(UV-vis)/螢光光譜儀(FL)、太陽光模擬器/光電流電壓量測(IV)做系統性的分析。
CdSe-T奈米晶由TOPO/HPA製備而成，當反應時間在10分鐘之後，可合成具有纖鋅礦結構之四足狀奈米晶，反應60分鐘的樣品其直徑及長度分別為4.6及16.7 nm。CdSe-H系列則由HDA/HPA製備，其形貌為分支狀而其最大直徑與長度分別為4.2與26.4 nm。與CdSe-T系列相比，因HDA在奈米晶表面的鍵結較強，會導致CdSe-T樣品之反應速率下降。由OA/ODE可製備出形貌為四足狀CdSe-O樣品，但此樣品的分支為全系列中最短的。晶種成長法可合成出具有閃鋅礦核種/纖鋅礦分支之四足狀奈米晶，且其產量最大，長度約為14 nm。
在四足狀樣品中Cd原子為電子施體，Se為受體。比較T60，H60及CdSe-SG樣品可發現其添加可增強OPV之光吸收能力及高平衡電荷載子流動性，可分別使短路電流(JSC)由9.6提升至10.3，10.8及10.9 mA/cm2，及效率由3.80提升至4.04，4.17及4.30 %。當CdSe-SG樣品的濃度由0增加至25及80 mg時，JSC由9.6提升至10.9再降至9.4 mA/cm2，同樣的效率由3.80提升至4.30再降至3.19 %，因此適當濃度CdSe的添加，有助於增益OPV元件中之電子傳導及光的吸收。
In this study, CdSe quantum dots (QDs) with different morphologies have been synthesized and applied as the donor in the active layer in the OPV devices. CdSe nanocrystals (NCs) are synthesized by using trioctylphosphine oxide (TOPO)/ hexylphosphonic acid (HPA), hexadecylamine (HDA)/HPA, and oleic acid (OA)/ octadecene (ODE) as surfactants. Besides, CdSe tetrapods with zinc-blend seeds and wurtzite arms are prepared by seed growth method. After that, CdSe NCs are mixed with P3HT:PCBM and used as the active layer of the OPV devices. The morphologies, structures, surface chemical states, chemical compositions, optical properties, and solar cell efficiencies are detected by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma – atomic emission spectrometer (ICP-AES), UV-visible absorption spectroscopy (UV-vis)/fluorescence (FL), and high fidelity solar simulator/IV measurement (IV), respectively.
CdSe-T NCs prepared by TOPO/HPA have tetrapod morphology and wurtzite structure when reacting after 10 mins. T60 sample has the diameter and length about 4.6 and 16.7 nm, respectively.
The morphology of CdSe-H samples prepared by HDA/HPA is branches, and the largest diameter and length is about 4.2 and 26.4 nm, respectively. Compared with CdSe-T samples, the bonding of HDA to the NC surface is stronger and the growth rate of NCs is lower. In terms of the CdSe-O prepared by OA/ODE, their morphology is tetrapod with the shortest length of arm among all samples. Seed growth synthesis can produce a large amount of CdSe tetrapods with length about 14.0 nm and zinc-blend core/wurtzite arm structure.
The Cd is electron supplier and Se is acceptor for the prepared CdSe tetrapods. The addition of T60, H60, and CdSe-SG samples can promote JSC from 9.6 to 10.3, 10.8, and 10.9 mA/cm2, and efficiency from 3.80 to 4.04, 4.17, and 4.30 %, respectively due to the enhancement in the light absorption ability and high balanced charge carrier mobility.
When the concentrations of CdSe-SG increases from 0 to 25 and 80 mg, JSC changes from 9.6 to 10.9 and 9.4 mA/cm2, and efficiency changes from 3.80 to 4.30 and 3.19 %, respectively, suggesting that appropriate CdSe content in the active layer is essential for the transport of electrons and light absorption in the OPV devices. |
