1998年Nozik首次用量子点作为光敏化剂，用无机半导体作为敏化剂制作新型敏化太阳能电池[1]。近年来，量子点敏化太阳能电池(QDSSCs)发展迅速。目前基于合金化策略制备的五元合金量子点获得了15.20%的认证效率[2]。QDSSCs具有原料来源广泛[3~7]、制备成本低廉、电池性能稳定以及光电转换效率较高的等优势，是最具有开发潜力的新一代太阳能电池[8]。QDSSCs的结构与DSSCs相同，都是由光阳极、电解液和对电极组成的典型的三明治结构[9]。为了实现量子点敏化剂更好的匹配[10~13]，QDSSCs的光阳极通常选用导带底低于量子点敏化剂的宽带隙半导体氧化物，以利于光生电子的注入[14]。量子点因其特有的“零维”空间结构而具有一些特殊的物理特性。“零维”空间结构为量子点注入了一些特殊的物理特性，如量子尺寸效应使量子点具有带隙可调性，可调节其光谱响应范围。与窄光谱染料敏化剂相比，宽光谱量子点敏化剂具有更高的吸光系数，能更充分地利用太阳光。同时，量子点敏化剂的多激子效应可在吸收一个光子的情况下激发多个电子，因此QDSSCs的理论光电转换率达到了惊人的44%，超过了单结半导体太阳能电池32%的传统光电转换效率[15]。随着研究的深入，TiO2阳极材料可广泛地应用于QDSSCs[16]和其他类型光伏电池中[17~21]。
作为TiO2的潜在替代品，其他合适的半导体氧化物也受到了关注。Hossain等[22]发现纳米结构的SnO2比纳米TiO2更有望成为QDSSCs中的光阳极材料。SnO2是一种p型宽带隙半导体[23]，具有比TiO2更高的电子扩散速率[24, 25]，因为其电子迁移率更高。这将使其成为QDSSCs光阳极材料的更好选择[26]。SnO2(3.6 eV)比TiO2(3.2 eV)的带隙更大，可以减少价带中的氧化空穴，有利于激子的复合作用，从而提高QDSSCs的稳定性。Pan等[27]制备的分层SnO2空心结构的多功能光电极，用于PbS量子点电池中其光电转换效率可达1.34。Lin等[23]用水热法合成的SnO2纳米粒子，结合CdS量子点使SnO2膜敏化后光电转换效率达到1.78%的。Wang等[28]首次合成了粒径可调SnO2纳米球，用于QDSSCs光电转换效率约为1.91%，随后又将纳米结构SnO2太阳能电池光电转换效率优化到3.68%[29]。
在复合电极薄膜中，底层的二氧化钛与导电玻璃结合更紧密，在光电转化中电子传输率更高[30]。本文将SnO2作为散射层与TiO2膜构成复合电极应用于ZnCuInSe量子点敏化太阳能电池中，改变光阳极膜的厚度以研究光阳极材料膜厚对电池效率的影响，并找出不同膜厚电池效率的变化趋势从而实现对电池的优化。
1 实验方法
1.1 实验用材料
乙酸锌(质量分数：99.99%)、醋酸铟、硒粉、升华硫和乙基纤维素，松油醇，醋酸锌(质量分数：99.99%)、十八烯胺(质量分数：97%)和十八烯(质量分数：90%)，碘化亚铜(质量分数：99.998%)，无水乙醇，聚乙二醇。未标注质量分数的化学品均为分析纯，溶剂包括去离子水。
1.2 SnO2 空心球的制备
图1
1.3 ZnCuInSe量子点的合成
将乙酸锌加入到OAm和ODE三颈烧瓶中，然后在N2中加热得到Zn源溶液。将CuI和In(OAc)3加入含有OAm、ODE和Zn源的溶液中[32]，将其加热至150℃后加入Se源溶液(0.4 mL DPP，0.5 mL OAm和0.04 g Se粉超声制得)，随后用配体交换程序从油相转移到水相。在震荡机中超声震荡3 min至均匀混合，然后将6 g P25粉末以少量多次的方式加入上述溶液后超声振荡至全溶，得到澄清透明溶液。然后向其中加入20 mL的松油醇和2.5 g的乙基纤维素乙醇溶液，超声震荡30 min使其充分混合，最后用旋转蒸发仪旋蒸5 h去除溶液中的乙醇，得到白色粘稠液体即TiO2浆料。
SnO2散射层浆料的制备：将1 g的SnO2粉末、0.1 g的乙基纤维素、0.2 g的聚乙二醇和5 mL乙醇置于球磨机球磨4 h，再加入0.1 g乙基纤维素和0.2 mL乙酰丙酮继续球磨2 h，最后用旋转蒸发仪去除乙醇得到SnO2糊剂。将SnO2糊剂丝网印刷到预先清洁的掺氟氧化锡导电玻璃(FTO)上，印刷后的有效面积为0.235 cm2。将TiO2透明层浆料和SnO2散射层浆料通过丝网印刷均匀地涂在洁净的FTO玻璃上，以15 μm的TiO2透明层作为底层，控制丝网印刷的层数以控制SnO2散射层的膜厚，然后0.5 mL OAm和0.04 g Se粉超声制得)，随后通过配体交换程序从油相转移到水相。
1.4 光阳极的制备和电池的组装
TiO2透明层浆料的制备：将无水乙醇、去离子水和冰醋酸按20:5:1的量置于圆底烧瓶，放入超声震荡机中超声震荡3 min至均匀混合，再将6 g P25粉末少量多次加入上述溶液超声振荡至全溶，得到澄清透明溶液。向其中加入20 mL松油醇和2.5 g的乙基纤维素乙醇溶液，超声震荡30 min使其充分混合，最后旋蒸5 h去除溶液中的乙醇，得到白色粘稠液体即为TiO2浆料。
SnO2散射层浆料的制备：将1 g 的SnO2粉末、0.1 g乙基纤维素、0.2 g聚乙二醇和5 mL乙醇置于球磨机球磨4 h，再加入0.1 g乙基纤维素和0.2 mL乙酰丙酮继续球磨2 h，最后旋蒸去除乙醇得到SnO2糊剂。将糊剂丝网印刷到预先清洁的掺氟氧化锡导电玻璃(FTO)上，有效面积为0.235 cm2。将TiO2透明层浆料和SnO2散射层浆料丝网印刷均匀地涂在洁净的FTO玻璃上，以15 μm TiO2透明层作为底层，控制丝网印刷的层数以控制SnO2散射层的膜厚，然后放入400℃的马弗炉中加热1 h，得到不同膜厚的光阳极。使用探针式表面轮廓仪测量样品膜厚，膜厚分别为6、9 和12 μm。
1.5 性能的测试和表征
用紫外-可见光谱仪(Lambada 950)表征吸附量子点的光阳极在(波长范围为500~1200 nm)可见光的响应波段。用X射线衍射仪(D8 Advance, BRUKER AXS GMBH, 德国)测试物质的化学成分。
用场发射扫描电子显微镜(Nova Nano SEM450, FEI Company) 表征材料的表面宏观形貌，用透射电子显微镜(JEOL-2100)测试微观形貌。用电化学工作站(CHI660E) 测试光伏性能和电化学阻抗，用IPCE量子效率测试仪(PTS-2-IQE) 测试入射光子的转换效率。对材料进行了X射线衍射(XRD)分析表征，管电压为40 kV、管电流为40 mA，使用Cu靶Kα 射线(λ=0.15406 nm)在扫描角度范围为10°~80°内对37.8°。测试了不同厚度的SnO2薄膜的电流密度-电压关系(J-V)。
2 实验结果
2.1 材料的形貌
图2
图2
SnO2材料的SEM图、SnO2材料的TEM照片以及SnO2材料的示意性模型
Fig.2
SEM images of SnO2 (a), TEM image of SnO2 (b,d) and schematic model of SnO2 (c)
图3
2.2 量子点敏化复合光阳极的光学性质
分别测试了有散射层(TiO2-SnO2)和没有散射层(TiO2)的量子点敏化复合光阳极的光学性质。图4给出了在波长范围为400~1000 nm内的紫外-可见吸收光谱。可以看出，吸附ZnCuInSe量子点的复合光阳极以及没有散射层的光阳极分别在900和940 nm附近出现起始吸收，散射层的加入使吸收范围向长波长方向偏移，证实复合光阳极具有更窄的带隙，有利于更好的光吸收而使光电转换效率提高。复合光阳极膜的吸波能力增强和吸波范围扩大，证明SnO2散射层能为QDSSCs的沉积提供更大的附着面积和空心球结构能促进量子点形成异质形核。这些结果表明，SnO2散射层能增强光阳极的吸光能力，有利于提高电池的光电转换效率。
图4
图4
无散射层TiO2膜和有散射层TiO2-SnO2膜的紫外-可见吸收(UV-Vis)光谱
Fig.4
UV-Vis curves of TiO2 film without scattering layer and TiO2-SnO2 scattering layer
2.3 光电性能
为了研究不同膜厚的SnO2薄膜对QDSSCs光伏性能的影响，进行了电流密度-电压(J-V)测试。填充因子(FF)、短路电流密度(Jsc)、开路电压(Voc)和光电转换效率(PCE)等光电参数列于表1。使用Cu2S对电极和多硫化物电解质制备典型的夹心型太阳能电池。图5a给出了量子点敏化太阳能电池的J-V特性曲线，表2列出电池的各项光伏参数。可以看出，只有TiO2薄膜吸附的ZnCuInSe量子点敏化太阳能电池，其Voc、Jsc以及FF的值分别为0.548 V、21.48 mA/cm2和0.53，光电转换效率为6.18%。散射层的增加，使电池的电流密度和填充因子明显提高。由表中数据可见，在6、9和12 μm三个膜厚范围内电池效率先提高后降低，膜厚为9 μm的电池效率达到峰值7.34%，且相应的Voc、Jsc以及FF的值都是三者中的最优值[35]。
表1 不同膜厚的光阳极散射层的光伏性能参数
Table 1
| Sample | Voc / V | Jsc / mA·cm-2 | FF | PCE / % |
|---|---|---|---|---|
| 15 μm TiO2 | 0.548±0.15 | 21.48±0.13 | 0.53 | 6.18 |
| 15 μm TiO2-6 μm SnO2 | 0.509±0.07 | 21.83±0.02 | 0.56 | 6.23 |
| 15 μm TiO2-9 μm SnO2 | 0.522±0.10 | 23.26±0.07 | 0.60 | 7.34 |
| 15 μm TiO2-12 μm SnO2 | 0.511±0.12 | 22.78±0.14 | 0.59 | 6.87 |
| 15 μm TiO2-9 μm SnO2-Solid | 0.595±0.08 | 20.94±0.11 | 0.56 | 6.98 |
图5
图5
光电性能分析示意图
Fig.5
J-V curves based on photoanodic scattering layers with different film thicknesses (a), IPCE spectra and Jsc curves (b) and Nyquist curves (c)
表2 不同膜厚光阳极散射层的EIS性能参数
Table 2
| Sample | Rs / Ω·cm2 | Rrec / Ω·cm2 | Cμ / mF·cm-2 | τn / ms |
|---|---|---|---|---|
| 15 μm TiO2 | 4.661 | 531.7 | 0.108 | 57.42 |
| 15 μm TiO2-6 μm SnO2 | 4.341 | 813.1 | 0.127 | 103.26 |
15 μm TiO2-9 μm SnO2 15 μm TiO2-12 μm SnO2 | 3.091 3.936 | 1030 914.3 | 0.168 0.141 | 173.04 128.92 |
对比图5a中的15 μm TiO2-6 μm SnO2与15 μm TiO2-9 μm SnO2两条曲线表明，随着膜厚的增加其FF、Jsc、Voc和PCE随之增加。这表明，随着样品膜厚的增加样品内部的连续性变强，入射光在光阳极内的多次反射或折射使光程增大，增大了量子点与入射光接触几率，使电池能更有效的利用入射光子，产生更多的光生电子。同时，TiO2-SnO2形成的同型半导体异质结能有效的分离光生电子空穴对、降低光阳极内部电子的复合率，使Jsc 增大。但是，由图中的15 μm TiO2-9 μm SnO2与15 μm TiO2-12 μm SnO2曲线可知，光阳极的膜厚继续增大超过优化效果的临界值时，产生的负面影响从而降低电池效率。其原因是，随着膜厚的增大光阳极薄膜晶体的缺陷增多，影响样品结构的连续性，增大了电池内部的电阻(Rs)，阻碍电子的传输，使电池的填充因子(FF)降低。同时，作为光生电子空穴对复合中心的缺陷增加，使电荷的复合率的提高，从而降低电池的Jsc和效率。
对四种不同膜厚的光阳极进行入射光子-电子转换效率(IPCE)测试，并对相应的IPCE积分得到电流密度(Jsc)，将曲线拟合得到图5b。图5b反映了不同波长太阳光的光电转换能力。四种曲线呈不规则梯形，相应的积分Jsc与由J-V得到的Jsc基本吻合。对太阳能电池电流的积分Jsc分别为21.48、21.84、23.26和22.78 mA·cm-2，与J-V测试得到的结果大致相同[36]。可以看出，电池的光响应范围相对于光阳极的吸收范围(图5a)均有些偏移，源于SnO2散射层中较大颗粒(220~240 nm)的光散射效应[27]。增加实心SnO2球在相同条件下的测试结果表明，空心结构的SnO2更有利于电解液的存储和氧化还原反应。由图5b可见，与不加散射层的电池相比，加散射层的样品电池其IPCE谱线的光吸收范围更宽和峰值最高，最高值可达到77%。同时，光电转换效率呈现先增加后减小的趋势。这表明，在散射层增加的过程中膜厚超过阈值使传输电子速率降低，导致其电流减小从而影响光电转换效率。
从图5c可以看出，不同电池组的奈奎斯特曲线均由两个半圆组成。高频(100 kHz~100 Hz)区域内的第一个小半圆反映电池的对电极与多硫电解液界面处的阻抗(RCE)，第二个大半圆显示在中频(10 Hz~100 Hz)区域内量子点敏化后的光阳极与电解液界面处的阻抗(Rrec)。中频区的半圆半径越大则Rrec越大，表明光阳极和电解液界面处的光生电子空穴对的复合率越小越有利于减小光生电子向外电路的传输损耗。图中的膜厚为9 μm时半圆半径最大，散射层电池的Rrec最大，从而说明其光阳极电解液界面处光生电子损耗最小。从表2可以看出，15 μm TiO2-9 μm SnO2样品电池的串联电阻(Rs)值最小，因此从Rs和Rrec可以看出其对应的填充因子(FF)最大。光生电子寿命为
式中，
3 结论
(1) 将用一步水热法制备的SnO2散射层用于QDSSCs，即在TiO2表面加入SnO2散射层对电池的优化效果显著，可延长光阳极中的光生电子寿命，减小Rs且能增加Rrce，从而提高FF和电池的效率。
(2) 光阳极膜的最佳厚度为散射层9 μm，透明层15 μm，此时光电转换效率最高。
(3) 过厚的膜易使光阳极龟裂而影响电子传输速率，太薄的膜影响量子点的吸收、入射光子的传输以及电解质的渗透和接触。
参考文献
Photosensitization of nanoporous TiO2 electrodes with InP quantum dots
[J].
Platinum modulates redox properties and 5-hydroxymethylfurfural adsorption kinetics of Ni(OH)2 for biomass upgrading
[J].
The impact of ZnO nanoparticle size on the performance of photoanodes in DSSC and QDSSC: a comparative study
[J].
Approach to quantum dot solar cells
[J].
量子点太阳电池的探索
[J].
阐述了探索量子点太阳电池的重要意义与物理构想, 简要介绍了两种不同结构组态的量子点太阳电池的光伏性能, 如p--i--n量子点太阳电池和量子点敏化太阳电池. 对发生在各种量子点(PbSe、PbS、PbTe、CdSe和Si)中的因碰撞电离而导致的多激子产生效应及其研究进展进行了重点评述, 并提出了设计与制作量子点太阳电池的若干技术对策. 可以预期, 具有超高能量转换效率、低制作成本与高可靠性的量子点太阳电池的实现,有可能对未来的光伏技术与产业产生革命性的影响.
Simultaneous epitaxy growth and photoelectrochemical performance of ZnO nanorod arrays and films
[J].The simultaneous epitaxial growth of vertical nanorod arrays and thin films of zinc oxide (ZnO) was realized on a gold-plated plane sapphire substrate via a simple chemical vapor deposition method. In this nanostructure, the vertical single crystal nanorods are hexagonal prism or cylindrical in shape, and are all grown on a ZnO thin film, so that the vertical nanorods are connected to each other through the beneath thin oxide ZnO film. In comparison with ZnO nanofilms, the prepared nanostructure has excellent photoelectrochemistry (PEC) performance with an incident photocurrent efficiency of 2.4 times that of the simple ZnO nanofilms; while its light energy conversion efficiency is 5 times that of ZnO nanofilms. Its excellent PEC performance can be attributed to its high surface area-to-volume ratio and the carrier transport channel provided by the supporter ZnO film. The mechanism for cooperative growth of ZnO nanorod arrays and thin films was proposed as follows: during the processing, Au liquefies and absorbs Zn atoms in the atmosphere forming alloys. After the alloy droplets were supersaturated ZnO begins to nucleate, and then ZnO film formed on the surface of the substrate. At the same time, Zn autocatalyzed (vapor-solid)VS growth and Au catalyzed (vapor-liquid-solid)VLS growth occurred, respectively forming hexagonal prism nanorods and cylindrical nanorods, and finally a vertical nanorod array was connected through the underneath thin ZnO film.
ZnO纳米棒阵列和薄膜的同步外延生长及其光电化学性能
[J].使用化学气相沉积法在a面蓝宝石衬底上同步外延生长氧化锌(ZnO)竖直纳米棒阵列和薄膜,研究了阵列和薄膜的光电化学性能。结果表明,纳米结构中的竖直单晶纳米棒有六棱柱形和圆柱形,其底部ZnO薄膜使竖直纳米棒互相联通。与ZnO纳米薄膜的比较表明,这种纳米结构具有优异的光电化学性能,其入射光电流效率是ZnO纳米薄膜的2.4倍；光能转化效率是ZnO纳米薄膜的5倍。这种纳米结构优异的光电化学性能,可归因于其高表面积-体积比以及其底部薄膜提供的载流子传输通道。本文分析了这种纳米结构的生长过程,提出了协同生长机理：Au液化吸收气氛中的Zn原子生成合金,合金液滴过饱和后ZnO开始成核,随后在衬底表面生成了ZnO薄膜。同时,还发生了Zn自催化的气-固(VS)生长和Au催化的气-液-固(VLS)生长,分别生成六棱柱纳米棒和圆柱形纳米棒,制备出底部由薄膜连接的竖直纳米棒阵列。
Synthesis and their optical characterizations of CdS quantum dots
[J].
CdS量子点的制备和光学性质
[J].
Preparation and microwave absorbtion performance of composite hollow carbon/Fe3O4 magnetic quantum dots
[J].
中空碳/Fe3O4磁性量子点复合材料的制备及其吸波性能
[J].将二氧化硅作为模板，通过原位聚合-溶剂热-煅烧工艺合成中空碳/Fe<sub>3</sub>O<sub>4</sub>磁性量子点复合材料，通过改变硝酸铁的添加量即相对碳含量来调控复合材料的电磁参数从而调节其微波吸收性能。使用扫描电镜(SEM)、透射电镜(TEM)表征了材料的结构和形貌，用拉曼光谱表征了材料的内部结构缺陷和相对石墨化程度，使用X射线晶体衍射(XRD)、X射线光电子能谱(XPS)表征了材料的晶体结构和化学组成。结果表明，厚度为2.55 mm的材料具有7.06 GHz的最大有效吸收带宽(EAB)，最小反射损耗值(RL<sub>min</sub>)可以达到-43 dB。这种材料优异的微波吸收性能，主要源自于其电磁匹配特性以及介电-磁损耗的协同作用。
The effect of graphene quantum dots/ZnS co-passivation on enhancing the photovoltaic performance of CdS quantum dot sensitized solar cells
[J].
Carbon counter-electrode-based quantum-dot-sensitized solar cells with certified efficiency exceeding 11%
[J].The mean power conversion efficiency (PCE) of quantum-dot-sensitized solar cells (QDSCs) is mainly limited by the low photovoltage and fill factor (FF), which are derived from the high redox potential of polysulfide electrolyte and the poor catalytic activity of the counter electrode (CE), respectively. Herein, we report that this problem is overcome by adopting Ti mesh supported mesoporous carbon (MC/Ti) CE. The confined area in Ti mesh substrate not only offers robust carbon film with submillimeter thickness to ensure high catalytic capacity, but also provides an efficient three-dimension electrical tunnel with better conductivity than state-of-art Cu2S/FTO CE. More importantly, the MC/Ti CE can down shift the redox potential of polysulfide electrolyte to promote high photovoltage. In all, MC/Ti CEs boost PCE of CdSe0.65Te0.35 QDSCs to a certified record of 11.16% (Jsc = 20.68 mA/cm(2), Voc = 0.798 V, FF = 0.677), an improvement of 24% related to previous record. This work thus paves a way for further improvement of performance of QDSCs.
Design of CdSe x S1- x /ZnS quantum dot sensitized solar cell
[J].
CsPbBr3 nanocrystal induced bilateral interface modification for efficient planar perovskite solar cells
[J].
Transparent MSe2@N-doped carbon film as a cathode for Co(Ⅲ/Ⅱ)-mediated bifacial dye-sensitized solar cells
[J].
透明MSe2@氮掺杂碳膜对电极用于钴电解质双面DSSC
[J].用层层自组装法制备一种M-TCPP(M=Ni、Fe)薄膜，然后原位硒化制备出MSe<sub>2</sub>和氮掺杂碳的复合透明膜(MSe<sub>2</sub>@NCF)，将其用作对电极并结合钴电解质的特点制备了双面DSSC。对MSe<sub>2</sub>@NCF的形貌、结构和电化学性能进行表征，并探讨了从正面和背面辐射DSSC时电池的电荷传输路线和光伏性能的区别。结果表明，NiSe<sub>2</sub>@NCF具有可与Pt相媲美的催化活性，用其组装的双面DSSC从正面辐射和背面辐射其PCE分别为8.19%和6.02%，与用Pt电极组装DSSC的PCE(8.46%和6.23%)接近。
Recent progress of non-noble metal catalysts in water electrolysis for hydrogen production
[J].
水电解制氢非贵金属催化剂的研究进展
[J].
Cosensitized quantum dot solar cells with conversion efficiency over 12%
[J].
Colloidal quantum dot solar cells
[J].
Design, fabrication and modification of metal oxide semiconductor for improving conversion efficiency of excitonic solar cells
[J].
SnO2 quantum dots modified N-doped carbon as high-performance anode for lithium ion batteries by enhanced pseudocapacitance
[J].
SnO2 quantum dots decorated reduced graphene oxide nanosheets composites for electrochemical supercapacitor applications
[J].
Manipulating resistive states in oxide based resistive memories through defective layers design
[J].
Self-assembled networked PbS distribution quantum dots for resistive switching and artificial synapse performance boost of memristors
[J].
Amorphous TiO2 buffer layer boosts efficiency of quantum dot sensitized solar cells to over 9%
[J].
PbS/CdS-sensitized mesoscopic SnO2 solar cells for enhanced infrared light harnessing
[J].Metal oxide semiconductors with lower lying conduction band minimum and superior electron mobility are essential for efficient charge separation and collection in PbS-sensitized solar cells. In the present study, mesoscopic SnO(2) was investigated as an alternative photoanode to the commonly used TiO(2) and examined comprehensively in PbS-sensitized liquid junction solar cells. To exploit the capability of PbS in an optimized structure, cascaded nPbS/nCdS and alternate n(PbS/CdS) layers deposited by a successive ionic layer adsorption and reaction method were systematically scrutinized. It was observed that the surface of SnO(2) has greater affinity to the growth of PbS compared with TiO(2), giving rise to much enhanced light absorption. In addition, the deposition of a CdS buffer layer and a ZnS passivation layer before and after a PbS layer was found to be beneficial for efficient charge separation. Under optimized conditions, cascaded PbS/CdS-sensitized SnO(2) exhibited an unprecedented photocurrent density of 17.38 mA cm(-2) with pronounced infrared light harvesting extending beyond 1100 nm, and a power conversion efficiency of 2.23% under AM 1.5, 1 sun illumination. In comparison, TiO(2) cells fabricated under similar conditions showed much inferior performance owing to the less efficient light harnessing of long wavelength photons. We anticipate that the systematic study of PbS-sensitized solar cells utilizing different metal oxide semiconductors as electron transporters would provide useful insights and promote the development of semiconductor-sensitized mesoscopic solar cells employing panchromatic sensitizers.
CdS/CdSe co-sensitized SnO2 photoelectrodes for quantum dots sensitized solar cells
[J].
Heterostructured perylene diimide (PDI) supramolecular nanorods with SnO2 quantum dots for enhanced visible-light photocatalytic activity and stability
[J].
Organic and hybrid resistive switching materials and devices
[J].The explosive increase in digital communications in the Big Data and internet of Things era spurs the development of universal memory that can run at high speed with high-density and nonvolatile storage capabilities, as well as demonstrating superior mechanical flexibility for wearable applications. Among various candidates for the next-generation information storage technology, resistive switching memories distinguish themselves with low power consumption, excellent downscaling potential, easy 3D stacking, and high CMOS compatibility, fulfilling key requirements for high-performance data storage. Employing organic and hybrid switching media in addition allows light weight and flexible integration of molecules with tunable device performance via molecular design-cum-synthesis strategy. In this review, we present a timely and comprehensive review of the recent advances in organic and hybrid resistive switching materials and devices, with particular attention on their design principles for electronic property tuning and flexible device performance. The current challenges posed with development of organic and hybrid resistive switching materials and flexible memory devices, together with their future perspectives, are also discussed.
An enhanced electrochemical energy conversion behavior of thermally treated thin film of 1-dimensional CoTe synthesized from aqueous solution at room temperature
[J].
Near infrared absorption of CdSe x Te1- x alloyed quantum dot sensitized solar cells with more than 6% efficiency and high stability
[J].
Mesoporous SnO2 spheres synthesized by electrochemical anodization and their application in CdSe-sensitized solar cells
[J].
Carrier generation and collection in CdS/CdSe-sensitized SnO2 solar cells Exhibiting unprecedented photocurrent densities
[J].CdS/CdSe-sensitized nanostructured SnO(2) solar cells exhibiting record short-circuit photocurrent densities have been fabricated. Under simulated AM 1.5, 100 mW cm(-2) illumination, photocurrents of up to 17.40 mA cm(-2) are obtained, some 32% higher than that achieved by otherwise identical semiconductor-sensitized solar cells (SSCs) employing nanostructured TiO(2). An overall power conversion efficiency of 3.68% has been achieved for the SnO(2)-based SSCs, which compares very favorably to efficiencies obtained by the TiO(2)-based SSCs. The characteristics of these SSCs were studied in more detail by optical measurements, spectral incident photon-to-current efficiency (IPCE) measurements, and impedance spectroscopy (IS). The apparent conductivity of sensitized SnO(2) photoanodes is apparently too large to be measured by IS, yet for otherwise identical TiO(2) electrodes, clear electron transport features could be observed in impedance spectra, tacitly implying slower charge transport in TiO(2). Despite this, electron diffusion length measurements suggest that charge collection losses are negligible in both kinds of cell. SnO(2)-based SSCs exhibit higher IPCEs compared with TiO(2)-based SSCs which, considering the similar light harvesting efficiencies and the long electron diffusion lengths implied by IS, is likely to be due to a superior charge separation yield. The resistance to charge recombination is also larger in SnO(2)-based SSCs at any given photovoltage, and open-circuit photovoltages under simulated AM 1.5, 100 mW cm(-2) illumination are only 26-56 mV lower than those obtained for TiO(2)-based SSCs, despite the conduction band minimum of SnO(2) being hundreds of millielectronvolts lower than that of TiO(2).
A novel, PbS quantum dot-Sensitized solar cell structure with TiO2-fMWCNTS nano-composite filled meso-porous anatase TiO2 photoanode
[J].
SnO2 hollow nanospheres enclosed by single crystalline nanoparticles for highly efficient dye-sensitized solar cells
[J].
Zn-Cu-In-Se quantum dot solar cells with a certified power conversion efficiency of 11.6%
[J].The enhancement of power conversion efficiency (PCE) and the development of toxic Cd-, Pb-free quantum dots (QDs) are critical for the prosperity of QD-based solar cells. It is known that the properties (such as light harvesting range, band gap alignment, density of trap state defects, etc.) of QD light harvesters play a crucial effect on the photovoltaic performance of QD based solar cells. Herein, high quality ∼4 nm Cd-, Pb-free Zn-Cu-In-Se alloyed QDs with an absorption onset extending to ∼1000 nm were developed as effective light harvesters to construct quantum dot sensitized solar cells (QDSCs). Due to the small particle size, the developed QD sensitizer can be efficiently immobilized on TiO2 film electrode in less than 0.5 h. An average PCE of 11.66% and a certified PCE of 11.61% have been demonstrated in the QDSCs based on these Zn-Cu-In-Se QDs. The remarkably improved photovoltaic performance for Zn-Cu-In-Se QDSCs vs Cu-In-Se QDSCs (11.66% vs 9.54% in PCE) is mainly derived from the higher conduction band edge, which favors the photogenerated electron extraction and results in higher photocurrent, and the alloyed structure of Zn-Cu-In-Se QD light harvester, which benefits the suppression of charge recombination at photoanode/electrolyte interfaces and thus improves the photovoltage.
High efficiency quantum dot sensitized solar cells based on direct adsorption of quantum dots on photoanodes
[J].
Alloying strategy in Cu-In-Ga-Se quantum dots for high efficiency quantum dot sensitized solar cells
[J].
Robust bifunctional phosphorus-doped perovskite oxygen electrode for reversible proton ceramic electrochemical cells
[J].
Quantitative analysis of light-harvesting efficiency and electron-transfer yield in ruthenium-dye-sensitized nanocrystalline TiO2 solar cells
[J].
