光散射与导模共振模型在薄膜太阳能电池结构设计中的应用

利用光散射与导模共振的理论,设计了一种薄膜太阳能电池的陷光结构,对硫属化合物薄膜太阳能电池进行了优化设计,选择多孔氧化铝薄膜(PAA)作为散射层,模型结构层厚度为:窗口层(AZO)320nm,缓冲层(In2S3)65nm,吸收层(SnS)660nm。研究结果表明,光散射与导模共振相结合的薄膜太阳能电池结构能够提高自身的光吸收率,其中由光散射结构提高的全光谱吸收率约为3%。本设计可以优化薄膜太阳能电池的吸收光谱,提高其对近红外波段的光吸收能力,在波长950nm位置的吸收率达到85%,增强了薄膜太阳能电池的光利用率。     

脉冲激光沉积法制备的ZnO薄膜的低阈值电抽运紫外随机激射

分别采用直流反应溅射法和脉冲激光沉积法在硅衬底上沉积ZnO薄膜, 用X射线衍射、扫描电镜、光致发光谱等手段对两种方法沉积的ZnO薄膜的结晶状态、 表面形貌和光致发光等进行了表征. 进一步对比研究了以上述两种方法制备的ZnO薄膜作为发光层的金属-绝缘体-半导体结构器件的电抽运紫外随机激射. 结果表明, 与以溅射法制备的ZnO薄膜作为发光层的器件相比, 以脉冲激光沉积法制备的ZnO薄膜为发光层的器件具有更低的紫外光随机激射阈值电流和更高的输出光功率. 这是由于脉冲激光沉积法制备的ZnO薄膜中的缺陷更少, 从而显著地减少了紫外光在光散射过程中的光损耗. 关键词： 随机激射 ZnO薄膜 脉冲激光沉积 溅射     

非周期微纳结构增强有机发光二极管光耦合输出的研究进展

有机发光二极管（OLED）具有功耗低、重量轻、色域宽、响应时间快及对比度高等优点,在全彩平板显示和固态照明等领域均显现出巨大的应用潜力,受到人们的广泛关注.然而,较低的光输出效率使得器件的外量子效率远低于内量子效率,这严重制约了OLED器件的发展和应用.因此如何提高OLED器件的光耦合输出效率已成为备受关注的研究课题.本文主要介绍了采用非周期微纳结构提高OLED器件光耦合输出效率的最新研究进展,对随机微纳透镜结构、光散射介质层、聚合物多孔散射薄膜、随机凹凸波纹结构及随机褶皱结构等多种对器件亮度分布和光谱稳定性无明显影响的光耦合输出技术进行了总结和讨论.最后,对提高OLED器件光耦合输出研究做了总结和展望.     

GaN基薄膜LED倒装芯片表面结构设计及光萃取效率研究

利用FDTD方法研究具有表面微纳结构氮化镓基倒装薄膜LED芯片的光萃取效率。通过优化表面结构并研究了器件的光萃取效率随p-Ga N层厚的变化。研究发现,具有表面光子晶体和六棱锥结构的器件的光萃取效率最大值比无表面微结构器件分别提高了56%和97%。尽管两种表面结构都能有效提高器件的光萃取效率,然而采用光子晶体的方案对p-Ga N厚度和腔长要求极为苛刻。采用六棱锥结构则不仅可以获得更高的光萃取效率,并且还将大大降低实验上材料外延生长及器件制备的难度。     

在电子传输层中添加PVK提高钙钛矿太阳能电池的性能

为了探究PVK对倒置平面异质结钙钛矿太阳能电池电子传输层的影响,向电子传输层PCBM中添加了一种富电子的聚乙烯基咔唑(PVK).采用原子力显微镜、PL光谱对薄膜进行了表征.实验结果表明:少量PVK的添加提高了覆盖在钙钛矿薄膜上PCBM层的平整度.当PVK的添加质量分数为4%时得到最佳器件效率,相比于纯PCBM作为电子传输层的器件,器件效率由(5.11±0.14)% 提升到(9.08±0.46)%.当PVK的添加质量分数大于4%时,粗糙度又趋于变大.PL光谱显示,少量PVK的加入使钙钛矿/电子传输层薄膜的PL强度降低,并使PL峰蓝移.研究表明:向PCBM中掺杂适量PVK能够改善钙钛矿/电子传输层/Al的界面接触,减少漏电流,并能够减少钙钛矿表面陷阱和晶界缺陷,减少电荷复合,从而提高了器件性能.     

利用Raman散射光谱研究铜铟镓硒薄膜表面的掺杂调节作用

主要研究了采用溅射后硒化方法制备CIGS(铜铟镓硒)薄膜太阳电池的吸收体材料中的表面层掺杂调节问题。并利用Raman散射谱分析研究了样品表面层特征峰的移用,研究结果表明: CIGS薄膜表面层由富In表面层调节为富CuGa表面层后,Raman特征峰位向高波数移动,表明薄膜表面的Ga含量随之变化,并导致表面能带的相应改变,经计算证实了富CuGa表面层样品较之富In表面层样品具有更高的表面能带,从而改善了以此材料为吸收层的太阳电池器件性能, V_oc提高了74 mV,填充因子上升8％,最终使器件转换效率η相应提高了约2％。提高了V_oc与FF。同时表明Raman散射谱作为一种灵敏的表面表征手段,在研究太阳电池吸收层表面状态时十分有力。     

在电子传输层中添加PVK提高钙钛矿太阳能电池的性能（英文）

为了探究PVK对倒置平面异质结钙钛矿太阳能电池电子传输层的影响,向电子传输层PCBM中添加了一种富电子的聚乙烯基咔唑(PVK)。采用原子力显微镜、PL光谱对薄膜进行了表征。实验结果表明:少量PVK的添加提高了覆盖在钙钛矿薄膜上PCBM层的平整度。当PVK的添加质量分数为4%时得到最佳器件效率,相比于纯PCBM作为电子传输层的器件,器件效率由(5.11±0.14)%提升到(9.08±0.46)%。当PVK的添加质量分数大于4%时,粗糙度又趋于变大。PL光谱显示,少量PVK的加入使钙钛矿/电子传输层薄膜的PL强度降低,并使PL峰蓝移。研究表明:向PCBM中掺杂适量PVK能够改善钙钛矿/电子传输层/Al的界面接触,减少漏电流,并能够减少钙钛矿表面陷阱和晶界缺陷,减少电荷复合,从而提高了器件性能。     

ITO界面调制层对GZO电极LED器件性能的影响

采用磁控溅射制备GZO和具有ITO界面调控层的GZO(ITO/GZO)透明导电薄膜作为大功率LED的电流扩散层,对比研究界面调控层对LED器件性能的影响。研究结果表明,ITO/GZO薄膜的透过率在可见光区达80%以上,退火后的ITO/GZO薄膜有较低的电阻率(1.15×10^-3 Ω·cm)。ITO调控层的介入能够调制GZO表面粗糙度,有利于改善LED外量子效率,降低GZO/p-GaN界面的接触势垒,提高LED器件的光电性 能。通过ITO界面调控后,LED器件20 mA驱动电流下的工作电压从9.5 V降低为6.8 V,发光强度从245 mcd 升到297 mcd,提高了20%;驱动电流为35 mA时,其发光强度从340.5 mcd 升到511 mcd,提高了50%。     

溶胶凝胶法制备透明IZO薄膜晶体管

采用溶胶凝胶法制备了非晶铟锌氧化物(a-IZO)薄膜,并作为薄膜晶体管(TFT)的有源层制备了a-IZO TFT。研究了IZO薄膜中铟锌比对薄膜性质及a-IZO TFT器件性能的影响。结果表明:溶胶凝胶法制备的IZO薄膜经低温(300℃)退火后为非晶结构,薄膜表面均匀平整、致密,颗粒大小为20 nm左右,并具有高透过率(>85%)。IZO薄膜中的铟锌比对薄膜的电学性能和TFT器件特性影响显著,增加In含量有利于提高薄膜和器件的迁移率。当铟锌比为3∶2时,所获得的薄膜适合于作为薄膜晶体管的有源层,制备的IZO-TFT经过相对低温(300℃)退火处理具有较好的器件性能,阈值电压为1.3 V,载流子饱和迁移率为0.24 cm2·V-1·s-1,开关比(Ion∶Ioff)为105。     

基于聚合物共混的有机场效应晶体管光电性能研究

采用聚合物共混的方法制备了体异质结薄膜,将其作为光敏半导体层制备了有机场效应光晶体管.利用原子力显微镜表征了共混薄膜的分相情况,探究了器件提高激子解离效率的机理,并对比了聚合物共混前后有机场效应晶体管的光电性能变化和相分离情况.结果表明：制备的聚合物共混光晶体管在微弱光线条件下(0.038 mW/cm²,808 nm)具有较高的光敏性(为10⁶).通过共混聚合物半导体材料制备体异质结薄膜可以有效地提高激子解离的效率,通过双层绝缘层能进一步降低光晶体管的暗电流,从而提高器件的光敏性.     

基于聚多巴胺/氧化锌复合阴极缓冲层的倒置聚合物太阳能电池的研究

利用多巴胺氧化自聚合形成聚多巴胺(PDA)与ZnO结合形成PDA/ZnO复合阴极缓冲层,制备了以P3HT:PC_(61)BM为活性层的倒置结构聚合物太阳能电池,通过改变PDA的自聚合时间来分析复合阴极缓冲层对器件性能的影响.实验发现,随着PDA的自聚合时间的增加,聚合物太阳能电池的光电转换效率先增大后减小,当自聚合时间为10 min时,相应器件光伏性能达到最优值,其开路电压V_(OC)为0.66 V,短路电流密度J_(SC)为9.70 mA/cm~2,填充因子FF为68.06%,光电转换效率PCE为4.35%.器件性能改善的原因是由于PDA/ZnO复合阴极缓冲层减小了ZnO与ITO之间的接触电阻,同时PDA中存在大量的氨基有利于倒置太阳能电池阴极对电子的收集.     

Enhanced photoelectrochemical performance of ZnO photoanode with scattering hollow cavities

Abstract ZnO nanoparticles with average diameter of 12 nm were used to fabricate ZnO photoanodes by electrohydrodynamic (EHD) technique for dye-sensitized solar cells (DSSCs). To enhance the light scattering and conversion efficiency, the ZnO film with scattering hollow cavities (HCs) was realized by calcining polystyrene spheres (PSs) in the film. The films had strong light scattering ability and the overall light to electricity conversion efficiency (η) was improved and reached 5.5% under illumination of simulated solar light (AM-1.5, 100 mW/cm²).     

Highly crystalline bilayer electron transport layer for efficient conjugated polymer solar cells

Solution processed solar cells are a promising renewable energy technology due to the low fabrication costs. The most commonly used electron transport layer for solution processed organic solar cells is ZnO. However, sol-gel derived ZnO is amorphous, which limits interfacial charge transport. In this study, we demonstrate a ZnO bilayer, composed of a nanoparticle ZnO and sol-gel derived ZnO layer, as the electron transport layer in polymer solar cells incorporating the novel polymer poly [(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di (2-octyldodecyl)-2,2′; 5′,2″; 5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD). Compared with the single layer sol-gel ZnO, the bilayer displayed enhanced crystallinity. Consequently, the interfacial transport from the active layer was improved, as evidenced by dark J-V and PL spectroscopy measurements. Solar cells incorporating this bilayer ZnO layer achieved PCE values exceeding 10%, a relative improvement of 25% compared to the sol-gel ZnO devices.     

Metal oxide buffer layer for improving performance of polymer solar cells

We report the application of aluminum doped ZnO (ZnO:Al) layer as a buffer on ITO glass for fabrication of non-inverted polymer solar cells. The ZnO:Al thin film was deposited using DC magnetron sputtering, with the thickness being varied from 23 to 100 nm. The devices showed most discernible improvements in their efficiencies when a thin layer of ZnO:Al film of thickness ∼40 nm was introduced. The observed enhancement in short circuit current density and open circuit voltage is likely attributed to the role of the ZnO:Al film as an optical tuner and an interfacial diffusion barrier. The result suggests that a metal oxide layer inserted between ITO and polymer layers can be a route for improving both efficiency and stability of polymer solar cells.     

ZnO/Ag/ZnO multilayer transparent electrode for highly-efficient ITO-Free polymer solar cells

Ultrathin metal film (UTMF) with a ZnO/Ag/ZnO hybrid structure was used as transparent electrode in a high-efficiency bulk heterojunction system for the fabrication of ITO-free polymer solar cells. The performance of the devices was carefully tuned through optical simulation using transfer matrix method by varying the thickness of ZnO seed layer and thin absorber layer. By employing appropriate device architecture, polymer solar cells fabricated using this UTMF-based electrode show efficiency as high as 9.49%, which is slightly higher compared to that of ITO-based device. From good agreement between the external quantum efficiency and optical modeling, it was found that the optimized microcavity configuration formed in UTMF-based device can greatly enhance the absorbance of the BHJ layer at longer wavelength as well as the favored exciton distribution for better charge transport and collection.     

Nanoimprint texturing of transparent flexible substrates for improved light management in thin‐film solar cells

We present a nanoimprint based approach to achieve efficient light management for solar cells on low temperature transparent polymer films. These films are particularly low‐priced, though sensitive to temperature, and therefore limiting the range of deposition temperatures of subsequent solar cell layers. By using nanoimprint technology, we successfully replicated optimized light trapping textures of etched high temperature ZnO:Al on a low temperature PET film without deterioration of optical properties of the substrate. The imprint‐textured PET substrates show excellent light scattering properties and lead to significantly improved incoupling and trapping of light in the solar cell, resulting in a current density of 12.9 mA/cm², similar to that on a glass substrate. An overall efficiency of 6.9% was achieved for a flexible thin‐film silicon solar cell on low cost PET substrate. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Short-circuit current improvement in CdTe solar cells by combining a ZnO buffer layer and a solution back contact

Conventional CdTe solar cells have a CdS window layer, in which an absorption loss of photons with more than 2.4 eV occurs through the CdS layer. A thinner CdS layer was applied to enhance light transmission and a ZnO buffer layer with a band gap of 3.3 eV was introduced to suppress shunting through the thinner CdS window layer. A 100-nm thick ZnO layer sputter-deposited at 300 °C had uniform coverage on a transparent conductive oxide (TCO) after a subsequent high-temperature process. The ZnO layer was effective in preventing shunting through the CdS window layer so that the open-circuit voltage and fill factor of the CdTe solar cells were recovered and the short-circuit current was enhanced over that of the conventional CdTe solar cell. In the ZnO/CdS/CdTe configuration, the short-circuit current was further improved throughout the visible wavelength region by replacing the Cu-metal contact with a Cu solution contact. As a result the short-circuit current from 21.7 to 26.1 mA/cm² and the conversion efficiency of the CdTe solar cell increased from 12 to 15% without antireflective coating. Our result indicates that the Cu solution back contact is a critical factor for achieving a higher cell efficiency in addition to ZnO buffer layer.     

Silver‐Based Nanoparticles for Surface Plasmon Resonance in Organic Optoelectronics

Organic optoelectronic devices including organic light‐emitting diodes (OLEDs) and polymer solar cells (PSCs) have many advantages, including low‐cost, mechanical flexibility, and amenability to large‐area fabrication based on printing techniques, and have therefore attracted attention as next‐generation flexible optoelectronic devices. Although almost 100% internal quantum efficiency of OLEDs has been achieved by using phosphorescent emitters and optimizing device structures, the external quantum efficiency (EQE) of OLEDs is still limited due to poor light extraction. Also, although intensive efforts to develop new conjugated polymers and device architectures have improved power conversion efficiency (PCE) up to 8%–9%, device efficiency must be improved to >10% for commercialization of PSCs. The surface plasmon resonance (SPR) effect of metal nanoparticles (NPs) can be an effective way to improve the extraction of light produced by decay of excitons in the emission layer and by absorption of incident light energy within the active layer. Silver (Ag) NPs are promising plasmonic materials due to a strong SPR peak and light‐scattering effect. In this review, different SPR properties of Ag NPs are introduced as a function of size, shape, and surrounding matrix, and review recent progress on application of the SPR effect of AgNPs to OLEDs and PSCs.     

Thickness study of Al:ZnO film for application as a window layer in Cu(In1−xGax)Se2 thin film solar cell

Structural, electrical and optical properties of Al doped ZnO (Al:ZnO) thin film of various thicknesses, grown by radio-frequency magnetron sputtering system were studied in relation to the application as a window layer in Cu(In_1−xGa_x)Se₂ (CIGS) thin film solar cell. It was found that the electrical and structural properties of Al:ZnO film improved with increasing its thickness, however, the optical properties degraded. The short circuit current density, J_sc of the fabricated CIGS based solar cells was significantly influenced by the variation of the Al:ZnO window layer thickness. Best efficiency was obtained when CIGS solar cell was fabricated with electrically and optically optimized Al:ZnO window layer.     

Improved performance of polymer solar cells by using inorganic,organic, and doped cathode buffer layers

The interface between the active layer and the electrode is one of the most critical factors that could affect the device performance of polymer solar cells. In this work, based on the typical poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester(P3HT:PCBM) polymer solar cell, we studied the effect of the cathode buffer layer(CBL) between the top metal electrode and the active layer on the device performance. Several inorganic and organic materials commonly used as the electron injection layer in an organic light-emitting diode(OLED) were employed as the CBL in the P3HT:PCBM polymer solar cells. Our results demonstrate that the inorganic and organic materials like Cs_2CO_3, bathophenanthroline(Bphen), and 8-hydroxyquinolatolithium(Liq) can be used as CBL to efficiently improve the device performance of the P3HT:PCBM polymer solar cells. The P3HT:PCBM devices employed various CBLs possess power conversion efficiencies(PCEs) of 3.0%–3.3%, which are ca. 50% improved compared to that of the device without CBL. Furthermore, by using the doped organic materials Bphen:Cs_2CO_3 and Bphen:Liq as the CBL, the PCE of the P3HT:PCBM device will be further improved to 3.5%, which is ca. 70% higher than that of the device without a CBL and ca. 10% increased compared with that of the devices with a neat inorganic or organic CBL.