Preparation of CdSe Nanocrystals with Different Morphologies and the Application in Organic Photovoltaic Devices

• Main Authors: Chen-Yu Chien, 簡振宇
• Other Authors: Kuan-Wen Wang
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/36329215288265930674

碩士 === 國立中央大學 === 材料科學與工程研究所 === 101 === 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.