Printed semi-transparent large area organic photovoltaic modules with power conversion efficiencies of close to 5 %

Currently, certified lab scale organic photovoltaic (OPV) cells reach efficiencies of more than 12% and life times of 10 years. For commercialization, it is necessary to understand which performance can be reached in fully printed large scale products. Our investigations show that large area, semi-transparent organic photovoltaic modules based on industrially available materials can achieve power conversion efficiencies of more than 4.8% on rigid substrates and 4.3% on flexible ones. The modules processed with a combination of large area coating and laser patterning with an active area of 68.76 cm² for flexible modules and a total area of 197.4 cm² for glass modules offer exceptionally high geometric fill factors of more than 94% and a transparency of more than 10%. The processing recipe and the layout of the modules are based on indications of optical and electrical simulations which allow to produce devices with only negligible losses in comparison to small single cell devices. Losses due to imperfect coating or patterning are identified by thermal imaging.     

Demonstration of the monolithic interconnection on CIS solar cells by picosecond laser structuring on 30 by 30 cm2 modules

In this paper, we present the selective structuring of all three patterns (P1, P2 and P3) of a monolithic interconnection of CIS (Cu(In,Ga)(S,Se)₂) thin film solar cells by picosecond laser pulses at a wavelength of 1064 nm. We show results for single pulse ablation threshold values and line scribing of molybdenum films on glass (P1), CIS on molybdenum (P2) and zinc oxide on CIS (P3). The purposes of these processes are the p‐type isolation (P1), cell interconnect (P2) and n‐type isolation (P3), which are required for complete cell architecture. The half micron thick molybdenum back electrode can be structured with a process speed of more than 15 m/s at about 15 W average power without detectable residues and damage by direct induced laser ablation from the back side (P1). The CIS layer can be structured selectively down to the molybdenum at process speeds up to 1 m/s at about 15 W average power, due to the precision of direct laser ablation in the ultrashort pulse regime (P2). The ZnO front electrode layer is separated by clean trenches with straight side walls at process speeds of up to 15 m/s at about 10 W average power, as a result of indirect induced laser ablation (P3). A validation of functionality of all processes is demonstrated on CIS solar cell modules (30 × 30 cm²). By replacing one state‐of‐the‐art process by a picosecond laser process at a time, solar efficiencies could be increased for P1 and P2 and stayed on a similar level for P3. After an optimization of the patterning processes in the R&D pilot line of AVANCIS, we achieved a new record efficiency for an all‐laser‐patterned CIS solar module: 14.7% as best value for the aperture area efficiency of a 30 × 30 cm² sized CIS module was reached. Copyright © 2014 John Wiley & Sons, Ltd.     

High precision processing of flexible P3HT/PCBM modules with geometric fill factor over 95%

Flexible OPV modules, based on P3HT:PCBM as absorber layer, were manufactured with a power conversion efficiency over 3% and for a total area of 3500 mm² consisting of 14 in series interconnected cells. The modules utilize the excellent mechanical and the outstanding optical properties of sputtered transparent ITO-Metal-ITO (IMI) electrodes deposited on the PET foil on the one hand, and the combination of large area slot-die coating with high resolution ultrafast laser patterning on the other hand. The manufacturing of modules with outstanding performance was found to be reproducible. The right combination of innovative electrodes and smart roll-to-roll compatible processing technologies demonstrates a viable path towards high efficient industrial module technology.     

“Layer‐Filter Threshold” Technique for Near‐Infrared Laser Ablation in Organic Semiconductor Device Processing

Although conventional laser ablation (CLA) method has widely been used in patterning of organic semiconductor thin films, its quality control still remains unsatisfied due to the ambiguous photochemical and photothermal processes. Based on industrial available near‐infrared laser source, herein, a novel “layer‐filter threshold” (LFT) technique is proposed, which involves the decomposition of targeted “layer‐filter” and subsequent explosive evaporation process to purge away the upper layers instead of layer‐by‐layer ablation. For photovoltaic device with structure of metal/blend/PEDOT:PSS/ITO/glass, the PEDOT:PSS layer as the “layer‐filter” is first demonstrated to be effective, and then the merged P1–P2 line and metal electrode layer are readily patterned through the “self‐aligned” effect and regulation of ablation direction, respectively. The correlation between laser fluence and explosive ablation efficacy is also investigated. Finally, photovoltaic modules based on classical P3HT:PC₆₁BM and low‐bandgap PBDT‐TFQ:PC₇₁BM systems are separately fabricated following the LFT technique. It is found that over 90% of geometric fill factor is achieved while device performances maintain in a limited change with increased number of series cells. In comparison to conventional laser ablation methods, the LFT technique does not require sophisticated instruments but reaches comparable processing accuracy, which shows promising potential in the fabrication and commercialization of organic semiconductor thin‐film devices.     

Surface treatment patterning of organic photovoltaic films for low-cost modules

This work describes a patterning technique for the photoactive layer of organic photovoltaic modules. We demonstrate the fabrication of efficient poly[3-(hexyl)thiophene-2,5-diyl]:[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) based organic photovoltaic modules through a specific surface treatment, based on the deposition of a fluorinated self assembled monolayer (SAM) on top of the bottom electric contact. Direct self-patterning of the photoactive layer is achieved by the high contact angle between the SAM and the polymer solution, while a smooth topography is created by combining two solvents with different surface tensions and boiling points in the polymer:PCBM solution. The resolution of the patterning is approximately 400 μm for modules based on a conventional cell architecture and 120 μm for an inverted architecture. As a result, we show 25 cm² P3HT:PCBM based organic photovoltaic modules with 10 series-connected cells, fabricated via roll-to-roll compatible deposition and patterning techniques.     

半导体中超快过程的研究

用飞秒脉冲激光技术研究了半导体中的超快过程．通过用超快光生电压谱对激光激发载流子的动量弛豫过程进行检测,得到在半导体硅中载流子的动量弛豫时间约为70飞秒,该过程与载流子与载流子的散射几率有关;对于锗硅量子点,由于载流子的散射几率下降,使动量弛豫时间增加至130飞秒．用超快反射谱法测量了载流子的能量弛豫过程和扩散过程,用高能量激光激发得到载流子的能量弛豫时间约为几个皮秒,这与载流子与声子的散射几率密切相关;而用低能量激光激发可得到光生载流子的扩散时间约为1百皮秒量级．     

Substrates,contacts and monolithic integration

Substrates and contacts play a critical role in thin-film solar cell device and module performance. They influence light trapping, film growth, impurity levels, doping, stability, yield and laser scribing for monolithic integration. The substrate is also a major cost factor, often accounting for the largest component of the module cost. The interaction between the substrates or contacts with the semiconductor layers can also limit the range of the subsequent semiconductor layer processing parameters. The panel and audience discussed these factors in relation to fabrication, performance and characterization of today's thin-film solar cells and modules. © 1997 John Wiley & Sons, Ltd.     

Metal cathode patterning for OLED by nanosecond pulsed laser ablation

Throughthe efforts of researchers for about two dec-ades since Tang invented organic light-emitting diode(OLED) in 1987[1],OLEDs are coming into practicalapplications as the displayfor some niche products ,suchas mobile phone,mp3 and etc .To make a matrix…     

飞秒激光刻蚀增强非晶硅薄膜太阳电池性能的研究

通过恒速移动线偏振飞秒激光焦点对非晶硅(a-Si) pin型薄膜太阳电池n型硅膜表面进行绒化刻蚀处理,形成不同周期间隔“凹槽”状结构.采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对刻蚀后薄膜表面形貌进行了表征,证实了刻蚀区域表面能够诱导晶态多孔微结构形成.比较了飞秒激光刻蚀前后a-Si太阳电池的光电转换效率(η)、开路电压、短路电流密度和填充因子.结果表明,当飞秒激光脉冲能量为0.75 J/cm2、刻蚀周期间隔为15μm时,太阳电池光电转换效率达到14.9％,是未经过激光刻蚀处理电池光电转换效率的1.87倍.同时,反射吸收谱表明,电池表面多孔“光俘获”微结构的形成对其光电转换效率的提高起到了关键作用.     

Interconnection of busbar‐free back contacted solar cells by laser welding

We are presenting the module integration of busbar‐free back‐junction back‐contact (BJBC) solar cells. Our proof‐of‐concept module has a fill factor of 80.5% and a conversion efficiency on the designated area of 22.1% prior to lamination. A pulsed laser welds the Al metallization of the solar cells to an Al foil carried by a transparent substrate. The weld spots electrically contact each individual finger to the Al foil, which serves as interconnect between different cells. We produce a proof‐of‐concept module using busbar‐free cell strips of 25 × 125 mm². These are obtained by laser‐dicing of a 125 × 125 mm² BJBC solar cell. The fill factor of this module is increased by 3.5% absolute compared with the initial cell before laser‐dicing. This is achieved mainly by omitting the busbars and reduction of the finger length. The improvement of the module fill factor results in an increase in the module performance of 0.9% absolute before lamination in comparison with the efficiency of the initial 125 × 125 mm² BJBC solar cell. Hence, this interconnection scheme enables the transfer of high cell efficiencies to the module. Copyright © 2014 John Wiley & Sons, Ltd.     

High‐Performance Organic Solar Cells with Spray‐Coated Hole‐Transport and Active Layers

In this study, we report high performance organic solar cells with spray coated hole‐transport and active layers. With optimized ink formulations we are able to deposit films with controlled thickness and very low surface roughness (<10 nm). Specifically we deposit smooth and uniform 40 nm thick films of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as well as films composed of a mixture of poly(3‐hexyl thiophene) (P3HT) and the C₆₀‐derivative (6,6)‐phenyl C61‐butyric acid methyl ester (PCBM) with thicknesses in the range 200–250 nm. To control film morphology, formation and thickness, the optimized inks incorporate two solvent systems in order to take advantage of surface tension gradients to create Marangoni flows that enhance the coverage of the substrate and reduce the roughness of the film. Notably, we achieve fill factors above 70% and attribute the improvement to an enhanced P3HT crystallization, which upon optimized post‐drying thermal annealing results in a favorable morphology. As a result, we could extend the thickness of the layer to several hundreds of nanometers without noticing a substantial decrease of the transport properties of the layer. By proper understanding of the spreading and drying dynamics of the inks we achieve spray coated devices with power conversion efficiency of 3.75%, with fill factor, short circuit current and open circuit voltage of 70%, 9.8 mA cm^?2 and 550 mV, respectively.     

Photovoltaic Devices: High‐Performance Organic Solar Cells with Spray Coated Hole‐Transport and Active Layers (Adv. Funct. Mater. 1/2011)

In this study, we report high performance organic solar cells with spray coated hole‐transport and active layers. With optimized ink formulations we are able to deposit films with controlled thickness and very low surface roughness (<10 nm). Specifically we deposit smooth and uniform 40 nm thick films of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as well as films composed of a mixture of poly(3‐hexyl thiophene) (P3HT) and the C₆₀‐derivative (6,6)‐phenyl C61‐butyric acid methyl ester (PCBM) with thicknesses in the range 200–250 nm. To control film morphology, formation and thickness, the optimized inks incorporate two solvent systems in order to take advantage of surface tension gradients to create Marangoni flows that enhance the coverage of the substrate and reduce the roughness of the film. Notably, we achieve fill factors above 70% and attribute the improvement to an enhanced P3HT crystallization, which upon optimized post‐drying thermal annealing results in a favorable morphology. As a result, we could extend the thickness of the layer to several hundreds of nanometers without noticing a substantial decrease of the transport properties of the layer. By proper understanding of the spreading and drying dynamics of the inks we achieve spray coated devices with power conversion efficiency of 3.75%, with fill factor, short circuit current and open circuit voltage of 70%, 9.8 mA cm^?2 and 550 mV, respectively.     

环形脉冲发生器中的超快光电导开关

一种新型的由电压充电传输线(VCTL)及本征硅光电导开关组成的极快电脉冲发生器巳研制成功。采用波长为1.06μm、脉宽为80ps的激光脉冲激励环形电路中的开关,可以获得具有极快上升下降沿(小于200ps)、宽度决定于环形线长、开关效率决定于负载的纳秒方波脉冲。     

Visualization of Photoexcited Carrier Responses in a Solar Cell Using Optical Pump—Terahertz Emission Probe Technique

We observed photoexcited carrier responses in solar cells excited by femtosecond laser pulses with spatial and temporal resolution using an optical pump-terahertz emission probe technique. We visualized the ultrafast local variation of the intensity of terahertz emission from a polycrystalline silicon solar cell using this technique and clearly observed the change in signals between a grain boundary and the inside of a grain in the solar cell. Further, the time evolution of the pump–probe signals of the polycrystalline and monocrystalline silicon solar cells was observed, and the relaxation times of photoexcited carriers in the emitter layers of crystalline silicon solar cells were estimated using this technique. The estimated relaxation time was consistent with the lifetime of the Auger recombination process that was dominant in heavily doped silicon used as an emitter layer for the silicon solar cells, which is difficult to obtain with photoluminescence method commonly used for the evaluation of solar cells.     

High‐Performance Pseudoplanar Heterojunction Ternary Organic Solar Cells with Nonfullerene Alloyed Acceptor

The vast majority of ternary organic solar cells are obtained by simply fabricating bulk heterojunction (BHJ) active layers. Due to the inappropriate distribution of donors and acceptors in the vertical direction, a new method by fabricating pseudoplanar heterojunction (PPHJ) ternary organic solar cells is proposed to better modulate the morphology of active layer. The pseudoplanar heterojunction ternary organic solar cells (P‐ternary) are fabricated by a sequential solution treatment technique, in which the donor and acceptor mixture blends are sequentially spin‐coated. As a consequence, a higher power conversion efficiency (PCE) of 14.2% is achieved with a V_oc of 0.79 V, J_sc of 25.6 mA cm^?2, and fill factor (FF) of 69.8% compared with the ternary BHJ system of 13.8%. At the same time, the alloyed acceptor is likely formed between two the acceptors through a series of in‐depth explorations. This work suggests that nonfullerene alloyed acceptor may have great potential to realize effective P‐ternary organic solar cells.     

透明介质材料的超快激光微纳加工研究进展

透明介质材料具有高透光性、高耐热性和良好的耐腐蚀性,被广泛应用于航空航天、微电子器件和光学元件等领域,这些应用对透明介质材料微纳加工的精度与质量提出了一定的要求。超快激光具有超高的峰值强度与超短的脉冲持续时间,可突破衍射极限并极小化热影响区,具有出色的加工精度与加工质量,为透明介质材料的微纳尺度加工提供了多样化的手段。综述了透明介质材料的超快激光微纳加工研究进展,包括超快激光加工透明介质材料的内部结构、相关机理和应用领域三个方面,并对透明介质材料的超快激光微纳加工进行了总结与展望。     

Influence of Blend Morphology and Energetics on Charge Separation and Recombination Dynamics in Organic Solar Cells Incorporating a Nonfullerene Acceptor

Nonfullerene acceptors (NFAs) in blends with highly crystalline donor polymers have been shown to yield particularly high device voltage outputs, but typically more modest quantum yields for photocurrent generation as well as often lower fill factors (FF). In this study, we employ transient optical and optoelectronic analysis to elucidate the factors determining device photocurrent and FF in blends of the highly crystalline donor polymer PffBT4T‐2OD with the promising NFA FBR or the more widely studied fullerene acceptor PC₇₁BM. Geminate recombination losses, as measured by ultrafast transient absorption spectroscopy, are observed to be significantly higher for PffBT4T‐2OD:FBR blends. This is assigned to the smaller LUMO‐LUMO offset of the PffBT4T‐2OD:FBR blends relative to PffBT4T‐2OD:PC₇₁BM, resulting in the lower photocurrent generation efficiency obtained with FBR. Employing time delayed charge extraction measurements, these geminate recombination losses are observed to be field dependent, resulting in the lower FF observed with PffBT4T‐2OD:FBR devices. These data therefore provide a detailed understanding of the impact of acceptor design, and particularly acceptor energetics, on organic solar cell performance. Our study concludes with a discussion of the implications of these results for the design of NFAs in organic solar cells.     

一种单次超快成像的新方法

本文报道了一种单次超快成像的新方法,该方法的时间分辨率仅由投影光的脉宽决定。我们用这种方法记录了有机玻璃中激光辐照损伤的全过程。     

A monolithically integrated high‐efficiency Cu(In,Ga)Se2 mini‐module structured solely by laser

Monolithically integrated Cu(In,Ga)Se₂ mini‐modules were fabricated in order to reduce the width of patterning related dead area. The Cu(In,Ga)Se₂ layers were prepared on soda‐lime glasses using the multistage process at low substrate temperature below 500 °C. A picosecond laser with a wavelength of 532 nm was used for all of the structuring processes (P1, P2, and P3) for the monolithic integration. A “lift‐off” type structuring was applied for P1 and P3, and an “ablation” type was for P2. The laser structuring was optimized to be minimizing the dead area width, and the width of about 70 µm was successfully achieved. A mini‐module, in which the optimized structuring processes were applied for the integration, demonstrated a certified efficiency of 16.6%. Copyright © 2015 John Wiley & Sons, Ltd.