TiO2光学间隔层增强聚合物太阳能电池光吸收的分析

基于共轭聚合物给体材料聚3-己基噻吩（P3HT）和富勒烯衍生物受体材料（6,6）-苯基-C61（PCBM）共混的体异质结结构的聚合物太阳能电池因其空穴载流子迁移率低而限制了P3HT:PCBM功能层厚度,从而影响了器件对入射光的吸收、在聚合物功能层和反射电极间插入TiO₂光学间隔层可以使器件内电场重新分布并改善器件的光吸收.基于薄膜传递矩阵法计算了不同的P3HT:PCBM功能层厚度和TiO₂插入层厚度的器件内光电场和光吸收.理论分析证明:器件结构为铟锡氧化物（ITO）（100 nm）/聚3,4-乙撑二氧噻吩/聚苯乙烯磺酸盐PEDOT:PSS（40 nm）/P3HT:PCBM/TiO₂/LiF（1 nm）/Al（120 nm）时,插入10 nm厚的TiO₂膜层可以使器件的聚合物功能层厚度在减薄25 nm的同时增加16.3%的光子吸收数,并且不明显降低功能层的激子分离概率,即功能层和TiO₂光学间隔层厚度分别约为75和10 nm时的器件性能为宜,此结果通过器件性能实验得以证实.     

共轭聚合物作为有机光电池电子受体的特性研究

以聚3-已基噻吩(P3HT)和聚对苯亚乙烯衍生物(MDMO-PPV)作为电子给体,聚 (TQ1)作为电子受体,制备并研究了聚合物给体/聚合物受体有机光伏电池性能。当给体P3HT、受体TQ1共混质量比为1∶1时,器件性能最佳。热处理会改变薄膜形貌,导致激子扩散到达界面的距离增加和激子分离界面数量下降,进而引起器件性能下降。溶剂效应对器件性能影响不明显。研究了相似能带结构给体聚合物对MDMD-PPV光电池性能的影响,发现结晶程度较低的给体材料会进一步导致器件性能降低。     

染料敏化太阳电池中TiO2颗粒界面接触对电子输运影响的研究

采用溶胶-凝胶法制备TiO₂浆料,通过丝网印刷技术印刷和不同温度曲线烧结TiO₂薄膜,并应用于染料敏化太阳电池(DSC).高分辨透射电子显微镜发现,低温下多孔薄膜中TiO₂颗粒之间呈现点接触,510 ℃烧结后TiO₂颗粒间由点接触变为面接触,近邻颗粒数增多,接触面积增大.同时采用强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)技术,研究了不同颗粒接触方式和接触面积对电子传输与复合的影响.结果表明:在420- 510 ℃之间,随着烧结温度提高,颗粒接触面积增大,电子传输时间(τ _d)缩短,电子有效扩散长度(L _n)增大,暗电流减小;当烧结温度达到550 ℃时,薄膜比表面积减小,多孔结构坍塌,表面态密度增大,电子传输时间(τ _d)增大.电池光伏特性研究表明:在480-510 ℃范围内烧结得到的TiO₂薄膜,电池短路电流密度(J_sc)最佳,电池效率(η)最好. 关键词： 界面接触 电子输运 暗电流 染料敏化太阳电池     

4,7-二（2-噻吩基）苯并噻二唑-3-辛基噻吩二炔在TiO2（100）表面吸附的密度泛函理论研究

采用密度泛函理论中的广义梯度近似（DFT/GGA）方法,在PW91/DNP水平上研究了4,7-二（2-噻吩基）苯并噻二唑-3-辛基噻吩二炔（简称P）的低聚合物P_n（n=1～5）的稳定性和化学活性.结果表明:随着聚合度增加,P_n的稳定性降低,化学活性增强.采用密度泛函理论与周期性平板模型相结合的方法,研究了化合物P在TiO₂（100）表面的吸附,通过吸附前后化合物P的Mulliken charge和前线轨道分析表明:当P吸附在TiO₂（100）表面时,P向TiO₂（100）表面转移0.692 e电荷,前线轨道能隙变窄.通过吸附前后TiO₂（100）表面的能带和态密度分析表明:在TiO₂（100）表面吸附了化合物P后,能带向低能区移动,且TiO₂中价带和导带间的禁带消失.理论预测的结果与实验值吻合.     

基于聚噻吩/聚己内酯共混物的有机薄膜晶体管

选择聚3-己基噻吩(P3HT)/聚己内酯(PCL)双晶共混体系制备了不同配比的共混物有机薄膜晶体管。电学性能研究发现,随着共混物中P3HT含量降低,薄膜晶体管的场效应迁移率、开关电流比和阈值电压等性能缓慢降低。当P3HT质量分数为40%时,共混物薄膜仍具有较好的场效应性能,迁移率为0.008 cm²·V^-1·s^-1,开关电流比为5×10³,阈值电压为45.5 V。原子力显微镜测试结果表明:共混物成膜时发生明显的垂直相分离,在界面处形成连续的半导体层,有利于载流子传输。     

纳米TiO2多孔薄膜电极平带电势的研究

采用光谱电化学方法研究了纳米TiO₂多孔薄膜电极的平带电势,获得了薄膜厚度以及TiCl₄处理对纳米TiO₂薄膜电极平带电势的影响情况,并研究了平带电势对染料敏化太阳电池光伏性能的影响.结果表明,可以通过检测纳米TiO₂电极平带电势的变化趋势来反映电池中TiO₂电极平带电势的变化趋势.随着TiO₂电极膜厚的增加,其平带电势将向正方向移动,导致对应电池的开路电压随之减小.另外,经 关键词： 平带电势 2')" href="#">纳米TiO₂ 染料敏化 太阳电池     

纳米TiO2颗粒/亚微米球多层结构薄膜内电荷传输性能研究

本文主要利用TiO₂亚微米球较强的光散射特性设计了纳米TiO₂颗粒/亚微米球多层结构光阳极, 并借助强度调制光电流谱(intensity-modulated photocurrent spectroscopy)、电化学阻抗谱(electrochemical impedance spectroscopy)和入射单色光光电转化效率(incident photon-to-current conversion efficiency), 研究亚微米球的引入对多层结构薄膜内缺陷态、电子传输时间、电子收集效率和界面电荷转移性能的影响. 强度调制光电流谱反映出亚微米球表面缺陷态少, 但其颗粒间接触不紧密, 导致在接触部位形成了势垒, 阻碍了电子的传输, 导致电子传输时间增长. 电化学阻抗谱结果表明不同多层结构电池界面复合无明显差别, 同时底层采用纳米TiO₂ 透明薄膜结构的电池, 其光利用率要明显高于底层采用亚微米球薄膜结构的电池, TiO₂费米能级电子填充水平也相对增大, 使得电池的光电转换效率得到提升. 多层结构复合薄膜电荷传输和光伏特性的研究, 为高效染料敏化太阳电池光阳极设计提供了实验基础.     

电化学合成聚噻吩薄膜提高光伏电池的开路电压

以铟锡氧化物(ITO)/聚(3,4-亚乙二氧基噻吩)-聚(苯乙烯磺酸)(PEDOT:PSS)为工作电极,采用电化学沉积法,直接在其上形成聚3-己基噻吩(P3HT)薄膜。其紫外可见吸收光谱的峰值约位于410nm处,吸收边延至610nm处,禁带宽度为2.04eV。测得其最高占有分子轨道(HOMO)能级为-5.21eV,而化学合成P3HT的HOMO能级为-5.02eV,这可能源于电化学合成聚噻吩的规整度比化学合成的要高。原子力显微镜AFM形貌结果表明电化学合成的P3HT中噻吩分子排列紧密,循环伏安扫描表明此P3HT薄膜的电化学性质稳定。采用该电化学合成的聚噻吩与富勒烯衍生物[6,6]-苯基-C61-丁酸甲酯(PCBM)复合而成的光伏电池的开路电压高达0.76V,这主要源于电化学合成聚噻吩HOMO能级的降低,因而揭示了提高光伏电池开路电压的新途径。     

阴极缓冲层对于不同惰性气氛气压退火处理的 P3HT∶PCBM光伏性能的影响

制备了基于聚(3-己基噻吩)(P3HT)与可溶性富勒烯衍生物(PCBM)共混体系的太阳能电池。通过改变活性层退火处理时惰性气氛环境的压强,在一定程度上实现对共混物相分离以及聚合物结晶度的控制,研究了LiF作为阴极缓冲层对不同压强下退火处理的器件性能的影响。实验发现,LiF层的关键作用在于稳定开路电压以及提升短路电流,从而带动转化效率整体提升。结果表明,LiF层可以改善器件活性层与金属电极接触的界面形态,而器件的最终性能则由活性层的微观形貌与电极界面形态共同决定。     

负偏压作用下染料敏化太阳电池界面及光电性能研究

太阳电池组件由于局部电压不匹配,其中部分电池可能较长时间工作在负偏压状态下,从而影响电池光电性能.借助拉曼光谱、电化学阻抗谱和入射单色光量子效率(IPCE)等测试手段,研究长期负偏压作用下染料敏化太阳电池光电性能的变化及其影响机理.拉曼光谱研究结果表明:电池在1000 h负偏压作用下,电解质中阳离子(Li⁺)会向光阳极(TiO₂电极)移动并嵌入TiO₂薄膜中;长期负偏压作用还会致使TiO₂/电解质界面阻抗增大和IPCE下降,导致电池开路电压升高和短路电流减小.通过加入苯并咪唑(BI)添加剂,经1000 h负偏压后电池的拉曼光谱实验表明,BI能在一定程度阻碍Li⁺的嵌入,电池具有较好的长期稳定性.不同负偏压下的老化实验进一步表明,通过加入添加剂能够使电池在长期负偏压下保持较好的稳定性. 关键词： 染料敏化 太阳电池 组件 负偏压     

Investigation of polymer/inorganic hybrid photovoltaic device using quantum dots as the interface modifier

CdS quantum dots (QDs) were introduced as an interface modifier in the poly(3-hexylthiophene) (P3HT)/TiO₂ nanorod arrays hybrid photovoltaic device. The presence of CdS QDs interlayer was found to provide enhanced light absorption, increased interfacial recombination resistance at the P3HT/TiO₂ interfaces, thus leading to a lower recombination rate of the electrons due to the stepwise structure of band edge in P3HT/CdS/TiO₂, which accounts for the observed enhanced photocurrent and photovoltage of the hybrid solar cells. The optimized performance was achieved in P3HT/CdS/TiO₂ hybrid solar cells after deposition of CdS QDs for 10 cycles, with a power conversion efficiency of 0.57 %, which is nearly ten times higher than that of P3HT/TiO₂. The findings indicate that inorganic semiconductor quantum dots provide effective means to improve the performance of polymer/TiO₂ hybrid solar cells.     

Photovoltaic Cells with TiO2 Nanocrystals and Conjugated Polymer Composites

Various compositional photovoltaic cells based on the blend of poly(3-hexylthiophene) (P3HT) as donors and TiO₂ nanocrystals as acceptors are fabricated and investigated. It is demonstrated that the blend ratio of P3HT and TiO₂ nanocrystals could greatly influence the performance of the photovoltaic cells. The maximum of 0.411% in power conversion efficiency under AM 1.5, 100mW/cm², and 44.4% of fill factor are obtained in the solar cell with the blend weight ratio 1:1 of P3HT and TiO₂ nanocrystals. The function of nanocrystal composition is discussed in terms of the results of photoluminescence spectroscopy, atomic force microscopy, transmission electron microscopy, and charge transport I-V curve.     

Direct imprinting of ordered and dense TiO2 nanopore arrays by using a soft template for photovoltaic applications

Highly ordered and dense TiO₂ nanopore arrays are directly nanoimprinted on a transparent conductive glass substrate by using a polymethylmethacrylate/polydimethylsiloxane (PMMA/PDMS) composite soft template, which is replicated from an anodic aluminum oxide (AAO) replica mold. Results indicate that heat infiltration under vacuum conditions can ensure complete filling of PMMA into the AAO pores, and that free-standing PMMA nanorods with an aspect ratio more than 5 can be obtained by adjusting the AAO pore depth based on a freeze-drying technique. TiO₂ nanopore arrays with different diameters from 30 to 300 nm and inter-pore distances between 70 and 450 nm can be easily fabricated by using the corresponding templates with different sizes. Preliminary solar cells are also assembled with a heterojunction of conjugated polymer/TiO₂ nanopore arrays. Results indicate that the construction of poly-(3-hexylthiophene) (P3HT)/TiO₂ nanopore arrays can be more helpful in quenching the PL emission of P3HT than that of P3HT/flat TiO₂ film, and a maximum efficiency of about 0.32% can be obtained for a photovoltaic device with a TiO₂/[6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM)/P3HT structure.     

Enhanced performance in organic photovoltaic devices with a KMnO4 solution treated indium tin oxide anode modification

<正>The properties of poly（3-hexylthiophene）:（6,6）-phenyl C₆₁ butyric acid methyl ester（P3HT:PCBM） organic photovoltaic devices（OPVs） with an indium tin oxide（ITO） anode treated by a KMnO₄ solution are investigated.The optimized KMnO₄ solution has a concentration of 50 mg/L,and ITO is treated for 15 min.The modification of ITO anode results in an enhancement of the power conversion efficiency（PCE） of the device,which is responsible for the increase of the photocurrent.The performance enhancement is attributed to the work function modification of the ITO substrate through the strong oxygenation of KMnO₄,and then the charge collection efficiency is improved.     

Performance and stability studies of inverted polymer solar cells with TiO2 film as a buffer layer

TiO₂ based inverted polymer solar cells (PSCs) with a structure of fluorine-doped tin oxide (FTO)/TiO₂/P3HT:PCBM/PEDOT:PSS/Ag presented excellent air stabilities,; the power conversion efficiency (PCE) of devices exhibited only 15 % decay as compared to the highest value while being exposed in air-condition for more than 20 days. Interestingly, an overall enhancement of PCE from 3.5 % to 3.9 % was observed while the PSCs were exposed in air-condition up to 3 days; the improvement of performance was attributed to the TiO₂ films’ oxygen and water protection effect and the oxidation of Ag, which will benefit to form an effective work function match with the HOMO of P3HT leading to improved ohmic contact. However, the performance slowly decreased when the exposure time remains longer due to the physical adsorbed oxygen. UV–ozone treatment on the TiO₂ films’ leads to the formation of a metal-deficient oxide that results in a decreased PCE for the devices. Finally, X-ray photo-emission spectroscopy (XPS) was used to analyze the compositional changes of the TiO₂ films while they were exposed in air-condition or treated by UV–ozone.     

Natural hybrid organic–inorganic photovoltaic devices

Natural hybrid organic–inorganic photovoltaic devices based on TiO₂ have been realized. Chlorophyll A (from anacystis nidulans algae), chlorophyll B (from spinach), carmic acid (from insect Coccus cacti L.), synthetic trans-β-carotene, natural fresh picked Morus nigra, and their mixtures have been used as an organic photo active layer to fabricate photovoltaic prototypes. In order to reduce the charge’s interfacial recombination, different thicknesses (5–45 nm) of Si layers, subsequently oxidized in air, were inserted between the TiO₂ and chlorophyll B. Scanning electron microscopy of TiO₂ and Si/TiO₂ systems shows the coexistence at least of four classes of nanoparticles of 60, 100, 150 and 250 nm in size. Auger electron spectroscopy of the Si L_2,3V V transition demonstrates the presence of silica and SiO_x suboxides. Photocurrent measurements versus radiation wavelength in the range 300–800 nm exhibit different peaks according to the absorption spectra of the organic molecules.All realized photovoltaic devices are suitable for solar light electric energy conversion. Those made of a blend of all organic molecules achieved higher current and voltage output. The Si/TiO₂-based devices containing chlorophyll B exhibited an enhanced photocurrent response with respect to those with TiO₂ only.     

Synthesis and application of the solar cell of poly(3-hexylthiophene)/Fe N/titanium dioxide nanocomposite material

A series of nanocomposites of poly(3-hexylthiophene) with Fe N-doped TiO₂ (P3HT/Fe N/TiO₂) were synthesized by the chemical method in situ. The structure of the prepared composites was characterized using X-ray diffraction patterns (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Optical and electrochemical properties were determined using UV-vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. These tests indicated that P3HT/Fe N/TiO₂ is a new p-n semiconductor. Two solar cells based on P3HT/Fe N/TiO₂ were manufactured and studied.     

Electronic processes at the interfaces between photoactive layers and TiO<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript> buffer layers in organic solar cells

The effect a layer of TiO_x located between a photoactive layer and a metallic Al electrode has on the photovoltaic properties of an organic solar cell based on P3HT:PC₇₀BM polymer is studied. The optimum thickness of the TiO_x layer at which the efficiency of the solar cells is highest and the TiO_x layer ensures the transfer of electrons from the photoactive polymer layer to the electrode while blocking vacancies is found to be 10 nm. The effect oxygen has on electronic processes during the operation of the photovoltaic cell is discussed.     

Photoconduction action spectra of regio-regular poly(3-hexylthiopene):TiO2 diodes

The development of polymer-based photovoltaic devices brings the promise of low-cost and lightweight solar energy conversion systems. This technology requires new materials and device architectures with enhanced efficiency and lifetime, which depends on the understanding of charge-transport mechanisms. Organic films combined with electronegative nanoparticles may form systems with efficient dissociation of the photogenerated excitons, thus increasing the number of carriers to be collected by the electrodes. In this paper we investigate the steady-state photoconductive action spectra of devices formed by a bilayer of regio-regular poly(3-hexylthiophene) (RRP3HT) and TiO₂ sandwiched between ITO and aluminum electrodes (ITO/TiO₂:RRP3HT/Al). Photocurrents were measured for distinct bias voltages with illumination from either side of the device. Heterojunction structures were prepared by spin coating a RRP3HT film on an already deposited TiO₂ layer on ITO. Symbatic and antibatic curves were obtained and a model for photocurrent action spectra was able to fit the symbatic responses. The quantum yield increased with the electric field, indicating that exciton dissociation is a field-assisted process as in an Onsager mechanism. Furthermore, the quantum yield was significantly higher when illumination was carried out through the ITO electrode onto which the TiO₂ layer was deposited, as the highly electronegative TiO₂ nanoparticles were efficient in exciton dissociation.     

Effect of a buffer layer, composition and annealing on the performance of a bulk heterojunction polythiophene/fullerene composite photovoltaic device

Post-annealing of P3HT/C₆₀-based plastic solar cells, composite ratio and, incorporation of a buffer layers at the ITO–polymer/fullerene composite interface and the polymer/fullerene composite–Al interface have shown significant improvement in the performance of the photovoltaic device, both in terms of open-circuit voltage and short-circuit current. The annealing temperature, time duration and P3HT/C₆₀ composite ratios have been optimized for the best performance of typical ITO/PEDOT:PSS/P3HT:C₆₀/LiF/Al solar cell. The C₆₀ content is very crucial because it improves the photocurrent in the beginning but after a certain value it leads to decrease in absorption, thereby decreasing the photocurrent.