Temperature-dependent morphology evolution of P3HT:PCBM blend solar cells during annealing processes

In this paper, the morphology evolution of [6,6]-phenyl-C-61(or 71)-butyric acid methyl ester (PC₆₁BM or PC₇₁BM) in poly(3-hexylthiophene) (P3HT) annealed at different temperatures was investigated. One result which was observed is that PCBM clusters aggregate more readily at higher annealing temperatures. The aggregation of PCBM could be avoided after coating the Al layer on the active layer, which is due to the hindering effect of the Al layer for the formation of PCBM clusters. SEM images show that the active layer with Al coating is smoother than that without Al layer. The performance of so-fabricated devices was analyzed with different annealing temperatures. Open-circuit voltage, fill factor and power conversion efficiency (PCE) of the devices were improved subsequently with increased annealing temperatures, while the absorption intensity of the devices was also improved. The P3HT:PC₆₁BM and P3HT:PC₇₁BM blend devices had highest PCEs of 4.55% and 4.84%, respectively. Crystallinity of the active layer is raised with higher annealing temperatures, which may result in the increased performance of devices.     

Graphene doping of P3HT:PCBM photovoltaic devices

We have introduced solution-processable functionalized graphene material (SPFGraphene) in P3HT/PCBM photovoltaic devices. The best results were obtained with a P3HT/PCBM (1:1) mixture with 10 wt% of graphene is open-circuit voltage (V_oc) of 0.64 V, a short-circuit current density (J_sc) of 5.3 mA/cm² and a FF of 0.41 which led to a power conversion efficiency of 1.4% at illumination at 100 mW/cm² AM1.5. This device takes advantage of the electron-accepting feature of fullerenes and the high electron transport capability of graphene. The results indicate that the addition of graphene enhances the performance of polymer photovoltaic cells.     

Effect of monodisperse Cu2S nanodisks on photovoltaic performance of P3HT/PCBM polymer solar cells

Hybrid solar cells using monodisperse Cu₂S nanodisks compositing with the mixture of poly (3-hexylthiophene):1-(3-methoxycarbonyl) propyl-1-pheny [6,6] C61 (P3HT:PC₆₀BM) as the active layer have been fabricated and characterized. The hybrid solar cells exhibit the highest efficiency of 1.35% when the weight ratio of P3HT:PC₆₀BM:Cu₂S is 1:0.8:0.224. The power conversion efficiency (PCE) of nanocomposite device is increased 22.7% comparing with that of the device based on pure P3HT/PC₆₀BM. It is due to that the effect of high-quality Cu₂S nanodisks with good dispersity contributes the increased electronic transportation in the active layer and results in the enhancement in photovoltaic performance. We also investigated the morphology of photoactive layer by microscope; it is found that the dispersity of nanomaterial in active layer is very important for device performance and improvement of carrier mobility.     

Composition and annealing effects in solution-processable functionalized graphene oxide/P3HT based solar cells

Characterization of a solution-processable functionalized graphene oxide (SPFGraphene oxide) was investigated by FT-IR spectroscopy and the result of elemental analysis showed that the isocyanate treatment results in the functionalization groups in SPFGraphene oxide. Doping SPFGraphene oxide to P3HT based solar cells induces absorbing spectra more strongly and a great quenching of the photoluminescence of the P3HT. With an increase in the SPFGraphene oxide content, the overall performances of the hybrid devices increases first, reaching the peak efficiency for the 10 wt% SPFGraphene oxide content, and then decreases. After annealing at 160 °C for different time durations, the device containing 10 wt% of SPFGraphene oxide for 10 min shows the best performance with a power conversion efficiency of 1.046%, an open-circuit voltage of 0.73 V, a short-circuit current density of 3.98 mA cm^?2 and a fill factor of 0.36 under simulated AM1.5G conditions at 100 mW cm^?2; The similar content one for 20 min shows η value of 1.013%, which is lower than the former one to a small extent for longer annealing duration. The graphene has the potential to act as the next-generation material in the photovoltaic devices and other applications for ease of preparation, low price, large surface area, high conductivity and excellent transparency.     

Effect of oxygen precipitates in solar grade silicon on minority carrier lifetime and efficiency of solar cells

The effect of oxygen precipitates on minority carrier lifetime and performance of solar cell was studied by means of Fourier Transform Infrared Spectroscopy (FTIR), quasi-steady state photoconductance (QSSPCD), optical microscope, spectrumresponse and solar cell efficiency test. The minority carrier lifetime and performance of solar cell reduced depend on oxygen precipitates. A few of oxygen precipitates have formed after single-step annealing; and they do not impact the efficiency dramatically. Pre-annealing at 650 ℃ for 4 h enhances the oxygen precipitation when it is subjected to middle temperature annealing. The solar cells performance decayed sharply. Especially annealing at 950 ℃ for 3 h, the V os and I sc of cells decrease 12% and 25% respectively. Few oxygen precipitates have formed in silicon after high temperature annealing at about 1050 ℃ whether pre-annealing is used or not, and the performance of cells is notbe affected.     

Effect of wetting solvent on poly(3-hexylthiophene) (P3HT) nanotubles fabricated via template wetting

Template wetting is a simple, solution based nanofabrication method that has been shown effective for a wide range of polymers. Like other solution based polymer processing methods, it is reasonable to expect that the choice of solvent will have a significant impact on the chain orientation in the final solid structure. Here we examine the impact of wetting solvent on the properties of 100 nm diameter poly(3-hexylthiophene) (P3HT) nanotubules made via template wetting. The degree of alignment of the P3HT backbone with the nanotubule axis as observed through dichroism in the FTIR spectrum was observed to depend on the strength of polymer–solvent interaction forces, observed experimentally through thermogravimetric analysis experiments. This solvent effect was not observed in other properties as neither the UV–Vis absorbance nor the hole mobility was observed to depend significantly on the wetting solvent. It is believed that the rigid rod structure and large side chain limited the degree of increase in the effective conjugation length and preventing even the aligned chains from being more tightly packed as would be necessary for an increase in inter-chain π-bond interactions sufficient to impact these performance characteristics of the material.     

Behavior of mixed multi-walled carbon nanotube/P3HT monolayer at the air/water interface

The sidewall structure of multi-walled carbon nanotubes (MWNTs) was successfully functionalized with poly(3-hexylthiophene) (P3HT) by a non-covalent bond method. P3HT plays an important role in dispersing MWNTs, and assists them to have a stable existence at the air/water interface. The behavior of mixed MWNT/P3HT monolayer at the air/water interface was investigated after obtaining a homogeneously dispersed solution. The effect of MWNT concentration on the mixed MWNT/P3HT monolayer was investigated using the pressure–area (π–A) isotherm, relaxation curve and transmission electron microscopy (TEM). The mixed MWNT/P3HT monolayer was transferred onto a solid substrate using the Langmuir–Blodgett (LB) technique with horizontal or vertical deposition. The multilayer film was delicately fabricated by repeated deposition of the ultra-thin film. Scanning electron microscopy (SEM) images revealed non-uniformity in morphology of the ultra-thin MWNT/P3HT films. The absorption intensity at 250 nm by UV/vis spectroscopy illustrates that a uniform formation of mixed MWNT/P3HT monolayer into multilayer film was successfully obtained by horizontal deposition. The current–voltage characteristic of the ultra-thin MWNT/P3HT film shows that the current increases linearly with the increasing voltage, which indicates that MWNT/P3HT film forms an ohmic contact with gold. And, the electric current was estimated to be mainly contributed by MWNTs.     

Unique structural features and electrical properties of electrospun conjugated polymer poly(3-hexylthiophene) (P3HT) fibers

This study examines and compares the internal structure conjugated polymeric fibers fabricated by electrospinning with cast films. Despite rigidity of polymer chain and the inability of its molecular chains to entangle to form viscoelastic jets, regioregular poly(hexyl-3-thiophene) (P3HT) exhibited the remarkable capability to be electrospun when the solution was subjected to gelation. In order to investigate the influence of additional mechanical stretching on the fibers, P3HT was electrospun with the aid of a rotating disc collector. Structure of electrospun fibers was probed via characterization techniques such as differential scanning calorimetry (DSC), Fourier transform infrared and photoluminescence (PL) spectroscopies. The findings indicated internal structural modifications developed within P3HT fibers, as a consequence of additional mechanical stretching induced by the rotating collector. Polarized FTIR and PL spectroscopies suggested that the molecular chains were aligned along the fiber axis. Electrical conductivity of iodine doped P3HT electrospun fibers was between 3 × 10³ S/m and 6 × 10³ S/m.     

Silicon solar cells: Physical metallurgy principles

This article reviews the physical metallurgy aspects of silicon solar cells. The production of silicon solar cells relies on principles of thermochemical extractive metallurgy, phase equilibria, solidification, and kinetics. The issues related to these processes and their impact on solar cell performance and cost are discussed. For more information, contact M.G. Mauk, Astro-Power, Solar Park, Newark, Delaware 19716-2000; (302) 366-0400, ext. 3016; fax (302) 283-0162; e-mail mauk@astropower.com.     

Aligned rrP3HT film: Structural order and transport properties

Aligned regioregular poly(3 hexyl thiophene), rrP3HT, thin films have been fabricated by a rubbing technique. Structural studies indicate orthorhombic crystalline domains (CDs) with c-axis aligned principally along the rubbing direction. The backbones of the macromolecules are stacked along the b-axis, forming a plane of parallel backbones with π-electron overlap and with side chains between the planes (along the a-axis). There is no π-overlap between these planes due to the long side chains along the a-axis. The optical and electronic properties are correlated with the anisotropic structure. Both for light polarized parallel and for light polarized perpendicular to the chain direction, the onset of photocurrent coincides with the onset of absorption. The larger photoconductivity observed with light polarized along the c-axis suggests the films are of sufficiently high quality to reveal the intrinsic anisotropy of the electronic structure.     

Metallization of polythiophenes II. Interaction of vapor-deposited Cr,V and Ti with poly(3-hexylthiophene) (P3HT)

X-ray photoelectron spectra of poly(3-hexylthiophene) (P3HT) films, metallized with vapor-deposited Cr, V and Ti, were used to study the nature of the metal-P3HT bonds formed with highly reactive metals. These metals cause similar changes in the S(2p) and C(1s) spectra. At coverages less than 3 Å, the spectral evidence indicates that metals react only with the sulfur atom of P3HT. At higher coverages, after the initial metal-S reaction, further reaction occurs between the already bonded metal and carbon.     

Fabrication and characterization of cuprous oxide: fullerene solar cells

Cuprous oxide (Cu₂O)-based solar cells with fullerene (C₆₀) were fabricated on indium tin oxide (ITO) by a spin-coating method. The microstructure and cell performance of the solar cells with the Cu₂O:C₆₀ structure was investigated. A photovoltaic device based on an ITO/Cu₂O:C₆₀ bulk heterojunction structure fabricated by the spin-coating method provided short-circuit current density of 0.11 mA cm^?2 and open-circuit voltage of 0.17 V under an Air Mass 1.5 illumination. The microstructures of the Cu₂O active layer were examined by using X-ray diffraction and transmission electron microscopy. The energy levels of the present solar cells are also discussed.     

Accelerated corrosion of MoO3-deposited copper

The accelerated oxidation kinetics of MoO₃-deposited copper were studied in the temperature range of 480–700 °C in air. The accelerated oxidation followed the parabolic-rate law, indicating that the process was diffusion-controlled. Oxygen diffusion along liquid channels in the oxide scale was inferred to be the rate-limiting step in the overall mechanism. The rate constant increased from 9.2 × 10⁻⁶ to 3.8 × 10⁻⁵ kg² m⁻⁴ s⁻¹ with increasing the deposit mass from 0.3 to 0.9 kg m⁻² at 700 °C.     

Different solvents effect on the performance of the solar cells based on poly(3-hexylthiophene):methanofullerenes

This paper reports the effect on the performance of the solar cells based on poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) with different casting solvents. These blend films are characterized by UV–vis absorption spectra, photoluminescence spectra, charge-transport dark J–V curve, X-ray diffraction pattern curve, and AFM images. The results indicate that high boiling point solvent leads to an enhanced self-organization of P3HT in the active layer, which causes an increased charge transport. Increased incident light absorption and higher carrier mobility in the active layer contribute to the enhancement in the device performance, the power conversion efficiency of 3.69% and fill factor up to 65.3% are achieved with 1,2,4-trichlorobenzene as casting solvent without further heat treatment under Air Mass 1.5, 100 mW/cm².     

Machine learning(ML)-assisted optimization doping of KI in MAPbI_3 solar cells

Perovskite solar cells have drawn extensive attention in the photovoltaic(PV) field due to their rapidly increasing efficiency. Recently, additives have become necessary for the fabrication of highly efficient perovskite solar cells(PSCs). Additionally, alkali metal doping has been an effective method to decrease the defect density in the perovskite film. However, the traditional trial-and-error method to find the optimal doping concentration is timeconsuming and needs a significant amount of raw materials. In this work, in order to explore new ways of facilitating the process of finding the optimal doping concentration in perovskite solar cells, we applied a machine learning(ML) approach to assist the optimization of KI doping in MAPbI_3 solar cells. With the aid of ML technique, we quickly found that 3% KI doping could further improve the efficiency of MAPbI_3 solar cells. As a result, a highest efficiency of 20.91% has been obtained for MAPbI_3 solar cells.     

Efficient and low cost devices for solar energy conversion: Efficiency and stability of some natural-dye-sensitized solar cells

Dye-sensitized solar cells, named by us Dye-Cells, are one of the most promising devices for solar energy conversion due to their reduced production cost and low environmental impact, especially those sensitized by natural dyes. The efficiency and stability of devices based on natural sensitizers such as mulberry (Morus alba Lam), blueberry (Vaccinium myrtillus Lam), and jaboticaba's skin (Mirtus cauliflora Mart) were investigated. Dye-Cells prepared with aqueous mulberry extract presented the highest P_max value (1.6 mW cm^?2) with J_sc = 6.14 mA cm^?2 and V_oc = 0.49 V. Photoelectrochemical parameters of 16 cm² active area devices sensitized by mulberry dye were constant for 14 weeks of continuous evaluation. Moreover, the cell remained stable even after 36 weeks with a fairly good efficiency. Therefore, mulberry dye opens up a perspective of commercial feasibility for inexpensive and environmentally friendly Dye-Cells.     

机械合金化＋热处理制备高纯Ti3SiC2粉体

以3Ti/Si/2C/0.2Al粉体为原料,采用机械合金化和真空热处理的方法合成了高纯度的Ti3SiC2粉体,并分析了粉体颗粒的外观形貌.结果表明,对3Ti/Si/2C/0.2A1粉体机械合金化4 h,可以生成Ti3SiC2和TiC的混合粉体.采用真空碳管炉对机械合金化粉体产物进行热处理,可以显著提高粉体中Ti3SiC2含量.热处理温度对粉体Ti3SiC2含量有很大的影响,过高或过低都不利于提高粉体中Ti3SiC3含量.在1150℃保温2 h得到的粉体产物Ti3SiC2含量最高,达到97.1 v01%.热处理产物粉体颗粒比较细小,适合做复合材料的原料.     

Improved open-circuit voltage and ambient stability of CsPbI_2Br perovskite solar cells by incorporating CH_3NH_3Cl

Inorganic cesium metal halide perovskites have gained research interest as absorbers in perovskite solar cells due to their superior thermal stability.Among these,CsPbI₂Br,with a narrower band gap than CsPbBr₃ and a better phase stability than CsPbI₃,has received tremendous interest of the researchers.However,CsPbI₂ Br takes adverse phase transfer easily with an exposure to the water vapor in ambient air which not only brings inconvenience for research...     

钙钛矿太阳能电池稳定性的研究进展

回顾了钙钛矿太阳能电池的发展历程,总结了影响钙钛矿太阳能电池稳定性的几个重要因素,包括水汽、氧气、光照和高温条件对钙钛矿层的化学稳定性以及电子传输层(ETL)、空穴传输层(HTL)和制备工艺对电池稳定性的影响。对稳定机制进行了分析,提出了改善稳定性的一些方法,并根据目前的研究成果展望了钙钛矿太阳能电池的发展趋势。     

高迁移率的钛掺杂氧化铟薄膜在晶硅/非晶硅异质结电池上的应用研究

采用钛掺杂氧化铟旋转靶制备透明导电薄膜应用在晶硅/非晶硅异质结电池上。在不同氧含量下,研究钛掺杂氧化铟薄膜(T100薄膜)的光电性能,同时对比分析ITO薄膜。在电镜下T100薄膜呈现出柱状结构,并且展示出优异的光学性能。T100薄膜最大载流子迁移率可以达到75.6 cm~2·(V·s)^-1。相比于ITO薄膜,T100薄膜具有优异的电学传导和透光率,因此在异质结电池量产线上电池转换效率可以实现0.26%的提升。