Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.     

质量比对基于CuInSe2/P3HT纳米复合材料光检测器件性能的影响

利用CuInSe2纳米材料与P3HT共混形成纳米复合材料,并由此构筑了具有高开关比的原理性光检测器件.研究发现,两种材料的混合比例对器件的性能有明显影响.随着CuInSe2纳米颗粒含量的增加,器件的开关比先增加后减小,而响应时间则一直减小.     

纳米结构TiO2/聚3-己基噻吩多孔膜电极光电性能研究

用光电流作用谱、光电流-电势图等光电化学方法研究了ITO/聚3-己基噻吩(ITO/ P3HT)膜和纳米结构TiO2/聚3-己基噻吩(TiO2/P3HT)复合膜的光电转换性质. 结果表明, P3HT膜的禁带宽度为1.89 eV, 价带位置为－5.4 eV. 在ITO/TiO2/ P3HT复合膜电极中存在p-n异质结, 在一定条件下异质结的存在有利于光生电子-空穴对的分离. P3HT修饰ITO/TiO2电极可使光电流发生明显的红移, 从而提高了宽禁带半导体的光电转换效率.     

HAXPES of protected ITO surfaces at the buried P3HT/ITO interface

The characterization of buried interfaces is difficult and often has to be performed by a post‐processing method where the interface is exposed. Hard energy X‐ray photoelectron spectroscopy offers the ability to tune the X‐ray energy and thereby change the information depth. In this work, an inorganic/organic interface was evaluated, namely the poly(3‐hexylthiophene) (P3HT) interface with indium tin oxide (ITO), with relevance to organic photovoltaic devices. P3HT/ITO buried interfaces were examined using three X‐ray energies where the ITO surface was prepared under different pretreatment conditions. The P3HT film protected the ITO surface from adventitious adsorbents and allowed for sensitivity to the buried ITO surface. Robust peak fitting parameters were obtained to model the O 1 s and In 3d lineshapes. The deconvolution of these lineshapes allowed for the clear identification of a surface layer on the ITO which is oxidized to a greater extent than the underlying bulk ITO. The surface oxide layer, composed of indium oxide and indium hydroxide, is deficient of oxygen vacancies and would therefore be expected to act as an insulating barrier on the ITO surface. Peak fitting conditions allowed for an estimation of the relative thicknesses of this insulating layer. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of polydispersity on the bulk‐heterojunction morphology of P3HT:PCBM solar cells

Bulk heterojunctions (BHJs) based on semiconducting electron–donor polymer and electron–acceptor fullerene have been extensively investigated as potential photoactive layers for organic solar cells (OSCs). In the experimental studies, poly‐(3‐hexyl‐thiophene) (P3HT) polymers are hardly monodisperse as the synthesis of highly monodisperse polymer mixture is a near impossible task to achieve. However, the majority of the computational efforts on P3HT: phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM)‐based OSCs, a monodisperse P3HT is usually considered. Here, results from coarse‐grained molecular dynamics simulations of solvent evaporation and thermal annealing process of the BHJ are shared describing the effect of variability in molecular weight (also known as polydispersity) on the morphology of the active layer. Results affirm that polydispersity is beneficial for charge separation as the interfacial area is observed to increase with higher dispersity. Calculations of percolation and orientation tensors, on the other hand, reveal that a certain polydispersity index ranging between 1.05 and 1.10 should be maintained for optimal charge transport. Most importantly, these results point out that the consideration of polydispersity should be considered in computational studies of polymer‐based OSCs. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 895–903     

Improvement of Power Conversion Efficiency of P3HT/PCBM Polymer Solar Cell Systems by Optimization of the Process Steps

In this work, different steps involved in the fabrication of polymer solar cells were optimized using P3HT/PCBM heterojunction. Steps included spinning speed for coating of the PEDOT:PSS layer, use of filter for the PEDOT:PSS layer, spinning speed for coating of the active layer, sequence of annealing of the active layer either before or after electrode deposition, and modification of the cooling mechanism (either by cooling rapidly or slowly after heating of the active layer). Investigation of these steps led to an improvement of the power-conversion efficiency (PCE) of the polymer solar cells, especially the last step involving the change of cooling mechanism, which improved PCE by 25%.     

P3HT与CdTe纳米枝晶p-n异质结敏化ZnO纳米管阵列的光电化学研究

采用电化学方法首先在ITO导电玻璃上制备了一维有序ZnO纳米管阵列,然后在ZnO纳米管阵列上采用电化学方法沉积纳米枝状CdTe,形成了纳米枝状CdTe包覆ZnO纳米管的CdTe@ZnO壳核式复合结构,最后在上述复合结构中旋涂一层P3HT薄膜形成P3HT包覆的P3HT@CdTe@ZnO复合薄膜. 以此复合薄膜为光活性层组装成半导体敏化太阳电池,研究了该类电池的光电转换性能,对该电池的工作原理进行初步研究,所得太阳电池能量转换效率最高达到1.38%.     

聚3-己基噻吩：非富勒烯太阳能电池中的量子效率损失和电压损失

聚3-己基噻吩(P3HT)以其合成工艺简单、成本低廉的优势,成为有机光伏领域中最具吸引力的电子给体材料之一。然而,目前P3HT: 非富勒烯太阳能电池的光伏性能仍然较差。在本工作中,我们证明了与P3HT: 富勒烯太阳能电池相比,较快的电荷转移态的非辐射衰减速率(K_nr)是导致P3HT: 非富勒烯太阳能电池中较低的量子效率和较高的电压损失的原因。然后,我们研究了基于非富勒烯受体ZY-4Cl的太阳能电池的工作机理。研究结果表明与P3HT: 非富勒烯体系相比,P3HT: ZY-4Cl中K_nr的降低改善了器件的量子效率,同时降低了电压损失。K_nr降低的原因可以部分归因于电荷转移态能量的增加。此外,给体分子和受体分子之间的距离(DA间距)的增大也是K_nr减少的重要原因。因此,我们得出结论：为了提高P3HT太阳能电池的性能,需进一步降低器件的K_nr,这可通过增加活性层中的DA间距来实现。     

聚3-己基噻吩：非富勒烯太阳能电池中的量子效率损失和电压损失

From the industrial perspective, poly(3-hexylthiophene) (P3HT) is one of the most attractive donor materials in organic photovoltaics. The large bandgap in P3HT makes it particularly promising for efficient indoor light harvesting, a unique advantage of organic photovoltaic (PV) devices, and this has started to gain considerable attention in the field of PV technology. In addition, the up-scalability and long material stability associated with the simple chemical structure make P3HT one of the most promising materials for the mass production of organic solar cells. However, the solar cells based on P3HT has a low power conversion efficiency (PCE), which is less than 11%, mainly due to significant voltage losses. In this study, we identified the origin of the high quantum efficiency and voltage losses in the P3HT: non-fullerene based solar cells, and we proposed a strategy to reduce the losses. More specifically, we observed that: 1) the non-radiative decay rate of the charge transfer (CT) states formed at the donor–acceptor interfaces was much higher for the P3HT: non-fullerene solar cells than that for the P3HT: fullerene solar cells, which was the main reason for the more severely limited photovoltage; 2) the origin of the high non-radiative decay rate in the P3HT: non-fullerene solar cell could be ascribed to the short packing distance between the P3HT and non-fullerene acceptor molecules at the donor–acceptor interfaces (DA distance), which is a rarely studied interfacial structural property, highly important in determining the decay rate of CT states; 3) the lower voltage loss in the state-of-the-art P3HT solar cell based on the 2, 2'-((12, 13-bis(2-butyldecyl)-3, 9-diundecyl-12, 13-dihydro-[1, 2, 5]-thiadiazolo[3, 4-e]thieno[2', 3': 4', 5']thieno[2', 3': 4, 5]p-yrolo[3, 2-g]thieno[2', 3': 4, 5]thieno[3, 2-b]indole-2, 10-diyl)bis(methanelylidene))bis(5, 6-dichloro-1H-indene-1, 3(2H)-dion-e) (ZY-4Cl) acceptor could be associated with the better alignment of the energy levels of the active materials and the longer DA distance, compared to those based on the commonly used acceptors. However, the DA distance was still very short, limiting the device voltage. Thus, improving the performance of the P3HT based solar cells requires a further increase in the DA distance. Our findings are expected to pave the way for breaking the performance bottleneck of the P3HT based solar cells.     

Molecular weight dependence of carrier mobility and recombination rate in neat P3HT films

The microstructure dependence of carrier mobility and recombination rates of neat films of poly 3‐hexylthyophene (P3HT) were determined for a range of materials of weight‐average molecular weights, M_w, ranging from 14 to 331 kDa. This variation has previously been shown to modify the polymer microstructure, with low molecular weights forming a one‐phase, paraffinic‐like structure comprised of chain‐extended crystallites, and higher molecular weights forming a semicrystalline structure with crystalline domains being embedded in an amorphous matrix. Using Charge Extraction by Linearly Increasing Voltage (CELIV), we show here that the carrier mobility in P3HT devices peaks for materials of M_w = 48 kDa, and that the recombination rate decreases monotonically with increasing molecular weight. This trend is likely due to the development of a semicrystalline, two‐phase structure with increasing M_w, which allows for the spatial separation of holes and electrons into the amorphous and crystalline regions, respectively. This separation leads to decreased recombination. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 31–35     

P3HT/非富勒烯受体异质结有机太阳电池

非富勒烯受体材料在分子设计、光吸收及能级等多方面具有极其丰富的可调控性, 使得基于非富勒烯电子受体的本体异质结有机太阳电池(BHJ OSC) 近年得以迅速发展。P3HT聚合物作为被广泛研究的第二代有机半导体材料, 其价格便宜、具有较好的结晶性以及优异的载流子传输性能, 是经典的电子给体材料。本文综述了近年来以P3HT聚合物为给体、非富勒烯类有机化合物为电子受体的有机太阳电池研究进展, 探讨了P3HT/非富勒烯受体BHJ OSC中, 影响器件效率提升的关键因素, 以及电子受体优化设计方面的相应要求。对基于P3HT/非富勒烯受体 BHJ OSC器件的研究前景进行了展望。     

Photo-oxidation and ozonization of poly(3-hexylthiophene) thin films as studied by UV/VIS and photoelectron spectroscopy

The kinetics and the mechanisms of degradation of thin P3HT layers have been investigated quantitatively for ozonization and photo-oxidation. Both, decay kinetics and product evolution of the polymer degradation are monitored by in situ UV/VIS and X-ray photoelectron spectroscopy (XPS). The degradation pathways of ozonization and photo-oxidation of P3HT turn out to be significantly different. Ozone attacks the thiophene units mainly by direct addition to the double bonds, leading to the loss of UV/VIS absorption, while the aliphatic side chains [1] are hardly affected. During photo-oxidation, the polymer is primarily attacked at the alkyl side chain which leads to the formation of reactive peroxide species. These subsequently cause the oxidation of sulfur and concomitantly the destruction of the thiophene ring, resulting in the loss of absorption. From the kinetics of the blue shift of the optical absorption it is concluded that the polymer is mainly attacked at the terminal thiophene rings the case of photo-oxidation whereas ozone attacks positions more or less randomly distributed along the chain. The rate of photo-oxidation under AM 1.5 conditions is at least one order of magnitude faster than the decomposition of P3HT by ozone.     

热处理对P3HT与PCBM共混体系光电性能的影响

The effect of annealing treatment on the photoelectric properties of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was analyzed by UV-Vis absorption spectroscopy, photoluminescence (PL) spectroscopy, X-ray diffraction, and solar cell performance. The UV-Vis absorption peaks of P3HT:PCBM thin filmshowed enhancement and a red-shift after thermal annealing. PL and XRD peak intensities increased by annealing treatment. A solar cell based on the blend of P3HT:PCBM was fabricated, and the device performance was significantly improved by thermal annealing. For devices heat-treated at 130 益, open circuit voltage of 0.55 V, short circuit current density of 9.87 mA·cm-2, fill factor of 60.1% and power conversion efficiency (PCE) of 3.26% were achieved under 100 mW·cm-2 air-mass 1.5 solar simulator illumination.     

基于聚合物给体/有机小分子/富勒烯受体的三元共混有机太阳能电池

成功构筑了基于聚合物给体P3HT/有机小分子TT-TTPA/富勒烯受体PC₆₁BM的三元共混有机太阳能电池. 共轭有机小分子TT-TTPA与PC₆₁BM有很好的相容性, 相分离很小. 溶剂退火和热退火时, 含量相对较少的TT-TTPA容易从P3HT相中脱离出来进入PC₆₁BM相, 增加P3HT的结晶空间, 从而提高P3HT的结晶度和相纯度. 通过引入少量的第三组分TT-TTPA, 制备的三元共混有机太阳能电池获得了4.41%的能量转换效率, 相对于P3HT/PC₆₁BM二元共混体系的效率(3.85%)提高显著.     

Thermal effect on microstructure vibration of SiO2 thin films

The microstructure of amorphous SiO₂ thin film is a random network structure in which a large amount of [SiO₄] is interconnected with a specific SiOSi bond angle. The SiO₂ thin films used in this paper were prepared by ion beam sputtering and electron beam evaporation deposition techniques. Two-dimensional correlation spectroscopy analysis techniques were used in this study. By measuring the infrared temperature spectrum, we obtained the two-dimensional correlation synchronous spectrum and asynchronous spectrum, and decomposed the in-phase and out-phase asymmetric stretching vibration characteristics of SiOSi. As the temperature increases, the spectral transmittance of the vibrating peak decreases, and the relative change of in-phase asymmetric stretching vibration absorption peak is higher than that of the out-phase asymmetric stretching vibration absorption peak.     

How to measure absolute P3HT crystallinity via 13C CPMAS NMR

We outline the details of acquiring quantitative ¹³C cross‐polarization magic angle spinning (CPMAS) nuclear magnetic resonance on the most ubiquitous polymer for organic electronic applications, poly(3‐hexylthiophene) (P3HT), despite other groups' claims that CPMAS of P3HT is strictly nonquantitative. We lay out the optimal experimental conditions for measuring crystallinity in P3HT, which is a parameter that has proven to be critical in the electrical performance of P3HT‐containing organic photovoltaics but remains difficult to measure by scattering/diffraction and optical methods despite considerable efforts. Herein, we overview the spectral acquisition conditions of the two P3HT films with different crystallinities (0.47 and 0.55) and point out that because of the chemical similarity of P3HT to other alkyl side chain, highly conjugated main chain polymers, our protocol could straightforwardly be extended to other organic electronic materials. Variable temperature ¹H NMR results are shown as well, which (i) yield insight into the molecular dynamics of P3HT, (ii) add context for spectral editing techniques as applied to quantifying crystallinity, and (iii) show why T_1ρ^H, the ¹H spin–lattice relaxation time in the rotating frame, is a more optimal relaxation filter for distinguishing between crystalline and noncrystalline phases of highly conjugated alkyl side‐chain polymers than other relaxation times such as the ¹H spin–spin relaxation time, T₂^H, and the spin–lattice relaxation time in the toggling frame, T_1xz^H. A 7 ms T_1ρ^H spin lock filter, prior to CPMAS, allows for spectroscopic separation of crystalline and noncrystalline ¹³C nuclear magnetic resonance signals. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.     

Monte Carlo morphological modelling of a P3HT:PCBM bulk heterojunction organic solar cell

To deepen the understanding of morphology evolution in bulk heterojunction P3HT:PCBM organic photovoltaics system by thermal treatment, domain‐size‐dependent interfacial energies were first determined by coarse‐grained molecular dynamics modelling and then used in Monte Carlo simulations of the morphology evolution. Thereby initial conditions associated with optimal interfacial surface area, continuous volume, as well as domain sizes, and spatial distributions of the phase separated domains were identified. In line with earlier studies, a 1:1 P3HT:PCBM blend ratio is found to exhibit the most efficient morphology for exciton dissociation and charge transport. Our simulations reveal that preseeding of P3HT crystal at the anode side prior to the annealing process will be instrumental to pin the formation of P3HT at the favorable electrode especially when seeding exceeds a threshold of 10% surface coverage, whereas denser seeding patterns beyond the threshold did not improve the active layer morphology further. The observed trilayer depth profile (in the absence of preseeded P3HT crystals) implies that the commonly used thickness 100 nm of the active layer is not ideal for ensuring that donor and acceptor phases dominate at opposite ends of the active layer. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 270–279     

One dimensional main-chain crystallization kinetics of poly(3-octylthiophenes) investigated by infrared spectroscopy

Time-resolved infrared spectroscopy has been used to study the melt crystallization behavior of poly(3-octylthiophenes) (P3OT), which is a typical conductive polymer among the family of poly(3-alkylthiophenes) (P3ATs). It is found that, during the isothermal crystallization process at high temperature, the alkyl side chains of P3OT always keep in disordered state, whereas the ordering packing of conjugated backbone takes place. In order to reveal the structural changes and the crystallization kinetics corresponding to the main-chain ordering process, two spectral regions that associated with π–π stacking and the effective conjugation length of P3OT have been analyzed in detail. The characteristic IR bands of crystalline and amorphous phase are identified in each spectral region. Moreover, a simple spectral method has been proposed to calculate the evolution of crystallinity during the isothermal crystallization process of P3OT. Of particular note, the distinct one-dimensional growth kinetic of P3OT crystal has been revealed by Avrami analysis.     

Effect of annealing on microstructure and mechanical properties of polypropylene random copolymer

In this work, polypropylene random copolymer (PPR) was taken as an example to study the changes of mechanical properties related to its microstructure evolution. Firstly, the toughness and fracture morphology were analyzed by notched Izod impact test and scanning electron microscope. Annealing at relative lower temperatures (<100°C), mechanical properties are slightly enhanced, which should be pointed out that significant improvements have been observed when annealing at relative higher temperatures (>100°C). Secondly, the study was conducted from the conventional differential scanning calorimetry, wide angle X-ray diffraction, and small-angle X-ray scattering to analyses the changes in the crystalline and amorphous regions. Dynamic thermomechanical analysis was employed to explore the changes of molecular mobility in samples after annealing at different temperatures. Moreover, to find out the stress transfer between the crystalline regions and the amorphous regions, we did further analysis of the typical stress–strain curves and proposed the mechanism of microstructure evolution during annealing process. The results shown that amorphous rearranged and formed thinner lamellae when annealing at relative low temperature. While annealing at higher temperatures, the mobile and rigid amorphous regions rearranged into more perfect lamellae and the density of stress transmitters was increased significantly.