半导体纳米晶的制备与表面调控及光伏应用

发布时间：2018-06-12 05:49

本文选题：纳米晶 + 可控制备　；参考：《中国科学院研究生院（上海技术物理研究所）》2014年博士论文

【摘要】：量子尺寸效应使半导体纳米晶的禁带宽度随尺寸减小而增大，在光学性质上表现为激子吸收波长随尺寸可调。而纳米晶自由载流子的集体振动与入射电磁波耦合会产生局域表面等离子体共振吸收和局域电磁场增强效应。半导体纳米晶的自由载流子浓度可随掺杂浓度改变的特性，，使得其局域表面等离子体共振可人工调控。激子吸收和局域表面等离子体共振吸收使纳米晶具有优异的光吸收特性，有利于减小光电转换器件吸收层厚度，为缩短光生载流子传输距离和降低制造成本提供新途径。本论文以新型太阳能电池吸光材料为出发点，为实现对太阳光的全谱利用效率，采用化学法制备纳米晶并实现材料尺寸和形貌可控制备，获得激子吸收在可见光区域的CdSe量子点和近红外区域的PbS量子点以及在近红外波段具有局域表面等离子体共振吸收效应的CuS纳米晶以及热电Bi2Se3纳米晶；通过纳米结构表面工程来调控纳米晶光学性质和材料稳定性；研究纳米晶表面调控对纳米晶太阳能电池性能的影响和载流子界面传输特性。具体的研究内容和获得的结果可归结为如下三个方面。 1、半导体纳米晶的可控制备：以十八碳烯和油胺为非极性溶剂，采用化学法在惰性气氛中制备半导体CdSe、PbS、CuS和Bi2Se3纳米晶。通过控制反应温度、时间和前驱体浓度实现纳米晶尺寸和形貌可控制备。所获得的CdSe、PbS纳米晶量子点激子吸收峰位于可见到近红外范围，其中CdSe激子吸收峰从520nm至610nm可调，PbS激子吸收峰从920nm至1055nm可调。采用超声化学法进一步简化在非极性溶剂中制备CuS纳米晶的工艺，用介质球散射理论和环境介电常数实验证实所制备的CuS纳米晶在近红外波段具有明显的局域表面等离子体共振效应。通过调节硒前驱体的反应活性，成功实现在非极性溶剂中制备热电Bi2Se3纳米晶。为半导体纳米晶光学性质研究和光伏应用提供了丰富的材料基础。 2、纳米晶表面与光学性质调控：采用表面配体交换技术改变CdSe、PbS纳米晶量子点的表面阻抗以提高纳米晶颗粒间载流子传输能力，发现表面改性和环境气氛、PH值对纳米晶化学稳定性和光学性质具有显著影响，通过进一步包覆无机壳层提高纳米晶化学稳定性和光学稳定性。通过配体表面掺杂技术改变CuS纳米晶自由载流子浓度来调控其局域表面等离子体共振波长。 3、纳米晶太阳能电池的制备与性能研究：采用旋涂成膜工艺制备PbS纳米晶太阳能电池吸光层，结合原子层沉积制备的TiO2透明电子传输层，构筑纳米晶/电子传输层异质结太阳能电池。利用I-V特性测试和交流阻抗谱测试对纳米晶太阳能电池的光伏性能和载流子界面传输特性进行初步研究，通过等效元件拟合阻抗谱获得纳米晶太阳能电池等效电路模型。
[Abstract]:Because of quantum size effect, the band gap of semiconductor nanocrystals increases with the decrease of size, and the optical properties of semiconductor nanocrystals show that the wavelength of exciton absorption is adjustable with the size of semiconductor nanocrystals. The collective vibration of nanocrystalline free carriers and the coupling of incident electromagnetic waves will produce local surface plasmon resonance absorption and local electromagnetic field enhancement effect. The free carrier concentration of semiconductor nanocrystals varies with the doping concentration, which makes the local surface plasmon resonance (SPR) of semiconductor nanocrystals artificially adjustable. Exciton absorption and local surface plasmon resonance absorption make nanocrystals have excellent optical absorption properties, which is beneficial to reduce the thickness of the absorption layer of optoelectronic conversion devices. In order to shorten the distance of photogenerated carrier transmission and reduce the manufacturing cost, this paper takes the new solar cell absorbent material as the starting point, in order to realize the full spectrum utilization efficiency of solar light. Nanocrystals were prepared by chemical method and the size and morphology of the materials were controlled. CdSe quantum dots with exciton absorption in visible region and PBS quantum dots in near infrared region, CuS nanocrystals and thermoelectric Bi2Se3 nanocrystals with local surface plasmon resonance absorption effect in near infrared band were obtained. The optical properties and material stability of nanocrystals were regulated by surface engineering of nanocrystals, and the effects of surface regulation on the performance of nanocrystalline solar cells and the transport characteristics of carrier interface were studied. The specific research contents and the obtained results can be summed up as follows. 1. Controlled preparation of semiconductor nanocrystals: using octadecene and oleamine as non-polar solvents, the semiconductors CdSePbSnCuS and Bi2Se3 nanocrystals were prepared in inert atmosphere by chemical method. The size and morphology of nanocrystals were controlled by controlling reaction temperature, time and precursor concentration. The exciton absorption peaks of CdSe-PBS nanocrystalline quantum dots are located in the near infrared region, in which CdSe exciton absorption peaks are tunable from 520nm to 610nm. The exciton absorption peaks of CdSe nanocrystalline quantum dots are adjustable from 920nm to 1055nm. Ultrasonic chemical method was used to further simplify the preparation process of CuS nanocrystals in non-polar solvents. The dielectric sphere scattering theory and environmental dielectric constant experiments show that the prepared CuS nanocrystals have obvious local surface plasmon resonance effect in near infrared band. The thermoelectric Bi2Se3 nanocrystalline was successfully prepared in nonpolar solvent by adjusting the reaction activity of selenium precursor. For semiconductor nanocrystalline optical properties and photovoltaic applications to provide a rich material basis. 2, nanocrystalline surface and optical properties control: surface ligand exchange technology to change the surface impedance of CdSePbS nanocrystalline quantum dots to improve nanocrystals Transport capacity of carriers between micrite particles, It is found that the chemical and optical properties of nanocrystals are significantly affected by surface modification and ambient pH value, and the chemical and optical stability of nanocrystals are improved by further coating the shell free layer. The local surface plasmon resonance wavelength was controlled by changing the free carrier concentration of CuS nanocrystals by ligand surface doping technology. 3. Preparation and performance of nanocrystalline solar cells: preparation of PBS nanocrystals by spin-coating process Crystal solar cell absorbent layer, A nanocrystalline / electron transport layer heterojunction solar cell was constructed by combining the transparent electron transport layer prepared by atomic layer deposition. The photovoltaic properties and carrier interface transport characteristics of nanocrystalline solar cells were preliminarily studied by I-V and AC impedance spectroscopy. The equivalent circuit model of nanocrystalline solar cells was obtained by equivalent element fitting impedance spectroscopy.
【学位授予单位】：中国科学院研究生院（上海技术物理研究所）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB383.1;TM914.4

【相似文献】