基于非对称光栅导模共振提高有机太阳能电池吸收效率的研究
发布时间：2018-09-12 18:58
【摘要】：有机太阳能电池(Organic Solar Cells,OSCs)由于其材料廉价、柔韧性和成膜性都较好、可低温操作以及可根据需要对分子进行修饰等特性,近年来,一直成为研究的热点。虽然有机材料易于制备,但是其较短的载流子扩散距离使得活性层的厚度较大时会降低的载流子收集效率,这一矛盾限制了OSCs器件的吸收,使得OSCs转换效率很低。近年来,有很多研究致力于改变OSCs的内部结构以提高活性层对入射光的捕获能力。在OSCs器件结构中引入金属纳米材料是一种行之有效的方法,例如,在OSCs中引入周期性金属光栅或在活性层中添加金属纳米颗粒,通过在金属与有机材料活性层界面形成表面等离子激元,并在局部区域形成较强的电磁场分布,从而能够很大程度提高活性层对光的吸收。但是将金属纳米结构与有机活性层直接接触时,金属材料会对光生载流子有一定的吸收,同时也会产生热电子辐射,因此活性层的吸收效率会受到一定的影响。另一方面,在含有一维金属纳米光栅的OSCs器件中,表面等离子激元只有在TM(横磁场)偏振的入射光下才能激发,而对于TE(横电场)偏振的入射光,吸收效率并没有明显的提高。本论文提出采用电介质材料构成非对称光栅来实现OSCs器件吸收效率的提高,具体光栅结构主要由作为活性层的P3HT:PCBM和作为电子传输层的PEDOT:PSS材料构成。该结构能够避免因为金属材料对光生载流子的吸收而产生损耗。在电介质材料构成的光栅结构中,通过采用合适参数的衍射光学元件和波导层的薄膜结构使得衍射光场与受调制波导泄露模之间耦合引起能量重新分布,从而在波导层产生场强增强的导模共振现象,这种近场的增强能够促进活性层材料的光的吸收。同时,非对称光栅能够打破对称光栅中的简并模式,在考察的波长范围为内产生更多的波导模式,从而提高OSCs器件的吸收效率的宽谱特性。本文主要研究内容:(1)简述OSCs的发展背景和意义,介绍其工作原理、以及影响OSCs活性层的吸收效率的因素。(2)介绍亚波长光栅特性,即导模共振异常现象。阐述导模共振异常的激发原理,及如何运用时域有限差分法在TE(横电场)和TM(横磁场)偏振模式进行电磁场分析。(3)第三章提出一种基于T型非对称二元光栅陷光结构的OSCs器件。分析发现,T型对称光栅结构中,光栅结构的周期P对对称光栅模式的位置和模式的变化起主要作用。在TE偏振模式下,在400~800 nm范围内,与对称结构相比,与对称结构相比,含有2个光栅脊的非对称光栅结构整体平均吸收效率提高了4.2%。与其相比,当非对称光栅结构中光栅脊的个数为3个时,整体平均吸收效率提高了约52%。(4)在第三章基础上,提出核壳-ITO非对称光栅结构的OSCs器件,发现核壳-ITO非对称光栅相比较T型光栅结构,导模形成的在有机活性层材料中的局域场分布更有利于器件吸收效率的提高。
[Abstract]:Organic solar cell (Organic Solar Cells,OSCs) has been a hot research area in recent years because of its cheap materials, good flexibility and film-forming properties, low temperature operation and modification of molecules as needed. Although organic materials are easy to prepare, the short carrier diffusion distance reduces the carrier collection efficiency when the thickness of the active layer is larger, which limits the absorption of OSCs devices and makes the conversion efficiency of OSCs very low. In recent years, many studies have been devoted to changing the internal structure of OSCs to improve the ability of the active layer to capture incident light. It is an effective method to introduce metal nanomaterials into the structure of OSCs devices, for example, to introduce periodic metal gratings in OSCs or to add metal nanoparticles to active layers. Through the formation of surface plasmon at the interface of the active layer of metal and organic materials and the formation of strong electromagnetic field distribution in the local region, the absorption of light in the active layer can be greatly improved. However, when the metal nanostructure is directly contacted with the organic active layer, the metal material will absorb the photogenerated carriers and generate hot electron radiation, so the absorption efficiency of the active layer will be affected to a certain extent. On the other hand, in OSCs devices containing one-dimensional metal nanocrystalline gratings, the surface plasma excitations can only be excited under the polarized incident light of TM (transverse magnetic field), but for the incident light polarized by TE (transverse electric field), the absorption efficiency is not significantly improved. In this paper, an asymmetric grating based on dielectric material is proposed to improve the absorption efficiency of OSCs devices. The grating structure is mainly composed of P3HT:PCBM as the active layer and PEDOT:PSS as the electron transport layer. The structure can avoid loss due to the absorption of photogenerated carriers by metal materials. In the grating structure of dielectric material, the coupling between the diffractive light field and the leaky mode of the modulated waveguide is caused by the appropriate parameters of the diffractive optical element and the thin film structure of the waveguide layer, which results in the redistribution of the energy. Thus the guided mode resonance in the waveguide layer is enhanced by the field intensity, and the near field enhancement can promote the light absorption of the active layer material. At the same time, the asymmetric grating can break the degenerate mode in the symmetric grating and generate more waveguide modes in the wavelength range of investigation, so as to improve the absorption efficiency of OSCs devices. The main contents of this paper are as follows: (1) the development background and significance of OSCs, its working principle and the factors affecting the absorption efficiency of the active layer of OSCs are introduced. (2) the characteristics of subwavelength grating, that is, the anomalous phenomenon of guided mode resonance, are introduced. The excitation principle of guided mode resonance anomaly and how to analyze the polarization mode of TE (transverse electric field) and TM (transverse magnetic field) by using finite-difference time-domain method are described. (3) in chapter 3, a novel OSCs device based on T-type asymmetric binary grating trapping structure is proposed. It is found that the periodic P of the grating structure plays a major role in the position and mode change of the symmetric grating mode in the structure of T type symmetric grating. In the polarization mode of TE, the average absorption efficiency of asymmetric grating structure with two ridges is increased by 4.2% compared with symmetric structure in the range of 400,800 nm. Compared with the asymmetric grating structure, when the number of grating ridges is 3, the overall average absorption efficiency is improved by about 52. (4) based on the third chapter, a core-shell OSCs device with asymmetric grating structure is proposed. It is found that the local field distribution of core-shell ITO asymmetric gratings in organic active layer materials is more favorable to the increase of absorption efficiency than that of T-type gratings.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM914.4
本文编号：2239933
[Abstract]:Organic solar cell (Organic Solar Cells,OSCs) has been a hot research area in recent years because of its cheap materials, good flexibility and film-forming properties, low temperature operation and modification of molecules as needed. Although organic materials are easy to prepare, the short carrier diffusion distance reduces the carrier collection efficiency when the thickness of the active layer is larger, which limits the absorption of OSCs devices and makes the conversion efficiency of OSCs very low. In recent years, many studies have been devoted to changing the internal structure of OSCs to improve the ability of the active layer to capture incident light. It is an effective method to introduce metal nanomaterials into the structure of OSCs devices, for example, to introduce periodic metal gratings in OSCs or to add metal nanoparticles to active layers. Through the formation of surface plasmon at the interface of the active layer of metal and organic materials and the formation of strong electromagnetic field distribution in the local region, the absorption of light in the active layer can be greatly improved. However, when the metal nanostructure is directly contacted with the organic active layer, the metal material will absorb the photogenerated carriers and generate hot electron radiation, so the absorption efficiency of the active layer will be affected to a certain extent. On the other hand, in OSCs devices containing one-dimensional metal nanocrystalline gratings, the surface plasma excitations can only be excited under the polarized incident light of TM (transverse magnetic field), but for the incident light polarized by TE (transverse electric field), the absorption efficiency is not significantly improved. In this paper, an asymmetric grating based on dielectric material is proposed to improve the absorption efficiency of OSCs devices. The grating structure is mainly composed of P3HT:PCBM as the active layer and PEDOT:PSS as the electron transport layer. The structure can avoid loss due to the absorption of photogenerated carriers by metal materials. In the grating structure of dielectric material, the coupling between the diffractive light field and the leaky mode of the modulated waveguide is caused by the appropriate parameters of the diffractive optical element and the thin film structure of the waveguide layer, which results in the redistribution of the energy. Thus the guided mode resonance in the waveguide layer is enhanced by the field intensity, and the near field enhancement can promote the light absorption of the active layer material. At the same time, the asymmetric grating can break the degenerate mode in the symmetric grating and generate more waveguide modes in the wavelength range of investigation, so as to improve the absorption efficiency of OSCs devices. The main contents of this paper are as follows: (1) the development background and significance of OSCs, its working principle and the factors affecting the absorption efficiency of the active layer of OSCs are introduced. (2) the characteristics of subwavelength grating, that is, the anomalous phenomenon of guided mode resonance, are introduced. The excitation principle of guided mode resonance anomaly and how to analyze the polarization mode of TE (transverse electric field) and TM (transverse magnetic field) by using finite-difference time-domain method are described. (3) in chapter 3, a novel OSCs device based on T-type asymmetric binary grating trapping structure is proposed. It is found that the periodic P of the grating structure plays a major role in the position and mode change of the symmetric grating mode in the structure of T type symmetric grating. In the polarization mode of TE, the average absorption efficiency of asymmetric grating structure with two ridges is increased by 4.2% compared with symmetric structure in the range of 400,800 nm. Compared with the asymmetric grating structure, when the number of grating ridges is 3, the overall average absorption efficiency is improved by about 52. (4) based on the third chapter, a core-shell OSCs device with asymmetric grating structure is proposed. It is found that the local field distribution of core-shell ITO asymmetric gratings in organic active layer materials is more favorable to the increase of absorption efficiency than that of T-type gratings.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM914.4
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相关期刊论文 前2条
1 陈乐;王庆康;沈向前;陈文;黄X;刘代明;;Absorption enhancement in thin film a-Si solar cells with double-sided SiO_2 particle layers[J];Chinese Physics B;2015年10期
2 刘瑞远;孙宝全;;有机物/硅杂化太阳能电池的研究进展[J];化学学报;2015年03期
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