TiO_(2)/SnO_(2)electron transport double layers with ultrathin SnO_(2)for efficient planar perovskite solar cells

The electron transport layer(ETL)plays an important role on the performance and stability of perovskite solar cells(PSCs).Developing double ETL is a promising strategy to take the advantages of different ETL materials and avoid their drawbacks.Here,an ultrathin SnO_(2)layer of~5 nm deposited by atomic layer deposit(ALD)was used to construct a TiO_(2)/SnO_(2)double ETL,improving the power conversion efficiency(PCE)from 18.02%to 21.13%.The ultrathin SnO_(2)layer enhances the electrical conductivity of the double layer ETLs and improves band alignment at the ETL/perovskite interface,promoting charge extraction and transfer.The ultrathin SnO_(2)layer also passivates the ETL/perovskite interface,suppressing nonradiative recombination.The double ETL achieves outstanding stability compared with PSCs with TiO_(2)only ETL.The PSCs with double ETL retains 85%of its initial PCE after 900 hours illumination.Our work demonstrates the prospects of using ultrathin metal oxide to construct double ETL for high-performance PSCs.

Inverted organic solar cells with solvothermal synthesized vanadium-doped TiO2 thin films as efficient electron transport layer

We investigated the effects of using different thicknesses of pure and vanadium-doped thin films of TiO2 as the electron transport layer in the inverted configuration of organic photovoltaic cells based on poly（3-hexylthiophene） P3HT：[6-6] phenyl-（6） butyric acid methyl ester（PCBM）. 1% vanadium-doped TiO2nanoparticles were synthesized via the solvothermal method. Crystalline structure, morphology, and optical properties of pure and vanadium-doped TiO2 thin films were studied by different techniques such as x-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and UV–visible transmission spectrum. The doctor blade method which is compatible with roll-2-roll printing was used for deposition of pure and vanadium-doped TiO2 thin films with thicknesses of 30 nm and 60 nm. The final results revealed that the best thickness of TiO2 thin films for our fabricated cells was 30 nm. The cell with vanadium-doped TiO2 thin film showed slightly higher power conversion efficiency and great Jsc of 10.7 mA/cm^2 compared with its pure counterpart. In the cells using 60 nm pure and vanadium-doped TiO2 layers, the cell using the doped layer showed much higher efficiency. It is remarkable that the external quantum efficiency of vanadium-doped TiO2 thin film was better in all wavelengths.

TiO_2 nanoparticle-based electron transport layer with improved wettability for efficient planar-heterojunction perovskite solar cell

The electron transport layer （ETL） plays an important role in planar heterojunction perovskite solar cell （PSCs）, by affecting the light-harvesting, electron injection and transportation processes, and especially the crystal- lization of perovskite absorber. In this work, we utilized a commercial TKD-TiO2 nanoparticle with a small diameter of 6 nm for the first time to prepare a compact ETL by spin coating. The packing of small-size particles endowed TKD-TiO2 ETL an appropriate surface-wettability, which is beneficial to the crystallization of perovskite deposited via solution-processed method. The uniform and high-transmittance TKD-TiO2 films were successfully incorporated into PSCs as ETLs. Further careful optimization of ETL thickness gave birth to a highest power conversion efficiency of 11.0%, which was much higher than that of PSC using an ETL with the same thickness made by spray pyrolysis. This TKD-TiO2 provided a universal solar material suitable for the further large-scale production of PSCs. The excellent morphology and the convenient preparation method of TKD-TiO2 film gave it an extensive application in photovoltaic devices.

钙钛矿太阳能电池电子传输层用SnO_(2)的溶剂热改性研究

SnO_(2)因具有高光学透过性、高电子迁移率,被作为电子传输材料广泛应用于钙钛矿太阳能电池(Perovskite Solar Cells,PSCs)中,但是溶胶—凝胶法制备的SnO_(2)薄膜,由于制备温度低,获得SnO_(2)薄膜晶粒的结晶性差,薄膜缺陷较多,会导致光电电子的复合,因而光电转化率较低。采用去离子水、甲醇、乙醇和异丙醇处理SnO_(2)电子传输层(Electron Transport Layers,ETLs),研究了水热溶剂热处理对SnO_(2)ETLs和PSCs性能的影响。采用XRD、SEM、接触角、AFM、UV-Vis、J-V曲线和IPCE对样品的物相、形貌、粗糙度、光学性能和光电性能进行表征。结果表明,采用溶剂热处理可以提高SnO_(2)的结晶度,提高薄膜的可见光透射率,增强ETLs与钙钛矿层的界面接触,有效提高电池的光电转换效率(Photoelectric Conversion Efficiency,PCE)。SnO_(2)经水热处理组装的PSCs光电性能最优,PCE为15.48%,比未处理电池的PCE 13.60%高出13.8%。另外,其开路电压(Open-circuit Voltage,V_(oc))为1.09 V,短路电流密度(Short-circuit Current Density,J_(sc))为19.32 mA·cm^(-2),填充因子(Fill Factor,FF)为73.18%。

SnO_(2)基钙钛矿太阳能电池的发展

有机无机杂化钙钛矿太阳能电池在2009年首次被报道,经过10多年的发展,钙钛矿电池认证光电转化效率已达25.5%。在电池中电子传输层起到阻挡空穴、传输电子、减少光生电子复合的作用,是钙钛矿太阳能电池的关键部分。与当前电子传输层应用最广泛的TiO_(2)相比,SnO_(2)拥有电子迁移率更高、可与电池其他部分能级匹配等优点。SnO_(2)为宽禁带半导体,不发生光降解,有利于电池的稳定。SnO_(2)作为电子传输层无需高温烧结,制备方法简单。2015年以SnO_(2)薄膜为电子传输层的电池被首次报道,其光电转换效率达到17.21%。随后,许多课题组也相继报道了基于SnO_(2)电子传输层的高性能钙钛矿太阳能电池。目前,以SnO_(2)为电子传输层的平面钙钛矿电池表现出高达25.2%的光电转换效率。采用SnO_(2)作为电子传输层的主要问题是:当SnO_(2)在高温煅烧时,晶粒会变大,并且体积膨胀会导致薄膜裂纹增多。与钙钛矿相比,SnO_(2)的导带要低得多,这可能会导致钙钛矿太阳能电池的电压降低。本文针对近几年SnO_(2)基钙钛矿电池的发展进行了系统综述,归纳了SnO_(2)的不同制备方法、掺杂和界面钝化对电子传输层的影响,并对SnO_(2)基钙钛矿电池未来的研究趋势进行了展望,以期为制备稳定高效的钙钛矿太阳能电池作参考。

High performance perovskite solar cells using TiO2 nanospindles as ultrathin mesoporous layer

Single crystal anatase TiO2 nanospindles （NSs） with highly exposed {101} facets were synthesized and employed as electron transport materials （ETMs） in perovskite solar cells （PSCs）. Time-resolved photoluminescence （TRPL） spectra revealed that the TiO2 NSs are more effective than TiO2 nanoparticles in accepting electrons from perovskite. Moreover. the TiO2 nanospindles further endowed the PSCs with good reproducibility and suppressed hysteresis. The best device with TiO2 NSs as ETMs yielded power conversion efficiency （PCE） of 19.6%, demonstrating that the home-made TiO2 NSs is a good ETM for PSCs.

介孔SnO_(2)的水热法制备及其在钙钛矿太阳能电池中的应用

自2009年钙钛矿太阳能电池问世以来,经过十几年的发展,电池效率从最初的3.8%提高到了25.7%。钙钛矿太阳能电池主要有平面结构和介孔结构两类,介孔结构的钙钛矿太阳能电池相对于平面结构多了一层介孔层。介孔层可以增大钙钛矿层和电子传输层的接触面积,有利于电子的提取和传输,从而减小电池的迟滞效应。采用水热法制备SnO_(2)介孔层,并将此介孔层应用于钙钛矿太阳能电池的电子传输层。主要研究了水热时间对介孔SnO_(2)电子传输层及钙钛矿太阳能电池的性能影响。通过XPS、SEM、UV-Vis、J-V和IPCE对样品的成分、形貌、光学性能和光电性能等进行了研究。结果表明:当水热时间从3 h增加到9 h时,SnO_(2)纳米片的直径从80 nm增加到了270 nm,介孔SnO_(2)层的厚度从70 nm增加到了350 nm。当水热时间为7 h时,电池的光电性能最佳,其光电转换效率为14.53%,开路电压为1.04 V,短路电流密度为19.29 mA·cm^(-2),填充因子为72.57%。

SnO_(2)退火温度对钙钛矿太阳能电池性能的影响

电子传输层是钙钛矿太阳能电池的关键部分,起到阻挡空穴、传输电子和减少电子空穴复合的作用。本研究采用低温溶液法制备SnO_(2)薄膜作为钙钛矿电池的电子传输层,研究SnO_(2)的退火温度对电子传输层微观形貌、物理性能以及钙钛矿太阳能电池性能的影响。结果表明:当退火温度为60、90、120和240℃时,SnO_(2)薄膜表面存在较多的孔隙;而退火温度为150、180和210℃时,薄膜表面孔隙较少。在实验温度下,制备的SnO_(2)薄膜为四方相,FTO玻璃上涂覆SnO_(2)薄膜后其透过率要优于空白FTO玻璃的透过率。当SnO_(2)退火温度为180℃时,薄膜的电子迁移率最高,钙钛矿电池具有最佳的传输电阻和复合电阻,所得电池的性能最优,其光电转换效率为17.28%,开路电压为1.09 V,短路电流为20.91 mA/cm^(2),填充因子为75.91%。

cPCN-Regulated SnO_(2) Composites Enables Perovskite Solar Cell with Efficiency Beyond 23%

Efficient electron transport layers(ETLs)not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells(PSCs)but also significantly affect the process of nucleation and growth of the perovskite layer.Herein,crystalline polymeric carbon nitrides(cPCN)are introduced to regulate the electronic properties of SnO_(2) nanocrystals,resulting in cPCN-composited SnO_(2)(SnO_(2)-cPCN)ETLs with enhanced charge transport and perovs-kite layers with decreased grain boundaries.Firstly,SnO_(2)-cPCN ETLs show three times higher electron mobility than pristine SnO_(2) while offering better energy level alignment with the perovskite layer.The SnO_(2)-cPCN ETLs with decreased wettability endow the perovskite films with higher crystallinity by retarding the crystallization rate.In the end,the power conversion efficiency(PCE)of planar PSCs can be boosted to 23.17%with negligible hysteresis and a steady-state efficiency output of 21.98%,which is one of the highest PCEs for PSCs with modified SnO_(2) ETLs.SnO_(2)-cPCN based devices also showed higher stability than pristine SnO_(2),maintaining 88%of the initial PCE after 2000 h of storage in the ambient environment(with controlled RH of 30%±5%)without encapsulation.

利用ZnCl_(2)原位钝化电子传输层提高量子点发光二极管性能

在量子点发光二极管(QLED)中,电子-空穴注入不平衡和量子点层/电子传输层间界面的荧光猝灭限制着QLED效率的提升。基于此,采用金属卤化物(ZnCl_(2))原位处理电子传输层方法来减少氧化锌(ZnO)电子传输层的氧空位,同时有效钝化其表面不饱和键,因此在一定程度上实现抑制量子点/电子传输层界面的荧光猝灭和提高QLED中的电子-空穴注入平衡的目的,最终得到了高亮度、高效率的QLED。原位钝化处理后的ZnO基QLED的最大亮度、峰值电流效率、峰值功率效率和峰值外量子效率(EQE)分别从未处理QLED的176800 cd/m^(2)、9.86 cd/A、8.38 lm/W和7.42%提高到219200 cd/m^(2)、15.14 cd/A、12.66 lm/W和11.65%。结果表明,ZnCl_(2)原位钝化ZnO电子传输层对QLED性能的提升起到重要的作用。

单层BiSbTeSe_(2)热电性能的第一性原理研究

本文利用第一性原理计算并结合玻尔兹曼输运方程,预测了一种热电性能优良的新型Bi_(2)Te_(3)基材料,即单层BiSbTeSe_(2)。通过系统计算单层BiSbTeSe_(2)的电子能带结构和热电输运性质,发现单层BiSbTeSe_(2)在300 K时的塞贝克系数达到最高值(522μV·K^(-1)),在500 K时功率因子与弛豫时间的比值最大为5.78 W·m^(-1)·K^(-2)·s^(-1)。除此之外,单层BiSbTeSe_(2)还具有较低的晶格热导率和较高的迁移率。在最佳p型掺杂下,单层BiSbTeSe_(2)在500 K时的热电优值ZT高达3.95。单层BiSbTeSe_(2)的优良性能表明其在300~500 K的中温热电器件领域具有潜在的应用价值,可以为进一步开发高性能Bi_(2)Te_(3)基热电材料提供设计依据。

Nitrogen‐doped tin oxide electron transport layer for stable perovskite solar cells with efficiency over 23%

Tin oxide has made a major breakthrough in high-efficiency perovskite solar cells(PSCs)as an efficient electron transport layer by the low-temperature chemical bath deposition method.However,tin oxide often contains pernicious defects,resulting in unsatisfactory performance.Herein,we develop high-quality tin oxide films via a nitrogen-doping strategy for high-efficiency and stable planar PSCs.The aligned energy level at the interface of doped SnO_(2)/perovskite,more excellent charge extraction and reduced nonradiative recombination contribute to the enhanced efficiency and stability.Correspondingly,the power conversion efficiency of the devices based on N‐SnO_(2) film increases to 23.41% from 20.55% of the devices based on the pristine SnO_(2).The N-SnO_(2) devices show an outstanding stability retaining 97.8% of the initial efficiency after steady-state output at a maximum power point for 600s under standard AM1.5G continuous illumination without encapsulation,while less than 50% efficiency remains for the devices based on pristine SnO_(2).This simple scalable strategy has shown great promise toward highly efficient and stable PSCs.

Influence of a UV-ozone treatment on amorphous SnO_(2) electron selective layers for highly efficient planar MAPbI3 perovskite solar cells

The effect of ultraviolet-ozone(UVO)irradiation on amorphous(am)SnO_(2) and its impact on the photoconversion efficiency of MAPbI3-based perovskite solar cells were investigated in detail.UVO treatment was found to increase the amount of chemisorbed oxygen on the am-SnO_(2) surface,reducing the surface energy and contact angle.Physicochemical changes in the am-SnO_(2) surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite grains.In addition,the Fermi energy of the UVO-treated am-SnO_(2) shifted upwards to achieve an ideal band offset for MAPbI3,which was verified by theoretical calculations based on the density functional theory.We achieved a champion efficiency of 19.01% with a statistical reproducibility of 17.01±1.34% owing to improved perovskite film densification and enhanced charge transport/extraction,which is considerably higher than the 13.78±2.15% of the counterpart.Furthermore,UVO-treated,am-SnO_(2)-based devices showed improved stability and less hysteresis,which is encouraging for the future application of up-scaled perovskite solar cells.

Efficient fully laser-patterned flexible perovskite modules and solar cells based on low-temperature solution-processed SnO2/mesoporous-TiO2 electron transport layers

Efficient flexible perovskite solar cells and modules were developed using a combination of SnO2 and mesoporous-TiO2 as a fully solution-processed electron transport layer （ETL）. Cells using such ETLs delivered a maximum power conversion efficiency （PCE） of 14.8%, which was 30% higher than the PCE of cells with only SnO2 as the ETL. The presence of a mesoporous TiO2 scaffold layer over SnO2 led to higher rectification ratios, lower series resistances, and higher shunt resistances. The cells were also evaluated under 200 and 400 lx artificial indoor illumination and found to deliver maximum power densities of 9.77 μW/cm^2 （estimated PCE of 12.8%） and 19.2 μW/cm^2 （estimated PCE of 13.3%）, respectively, representing the highest values among flexible photovoltaic technologies reported so far. Furthermore, for the first time, a fully laser-patterned flexible perovskite module was fabricated using a complete three-step laser scribing procedure （P1, P2, P3） with a PCE of 8.8% over an active area of 12 cm^2 under an illumination of 1 sun.

A low-temperature TiO2/SnO2 electron transport layer for high-performance planar perovskite solar cells

Conventional titanium oxide(TiO2) as an electron transport layer(ETL) in hybrid organic-inorganic perovskite solar cells(PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperatureprocessed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO2/tin oxide(SnO2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO2/SnO2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO2/SnO2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO2 and SnO2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency(PCE) of 19.11% with an open-circuit voltage(Voc)of 1.15 V, a short-circuit current density(Jsc) of 22.77 mA cm^-2,and a fill factor(FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO2/SnO2 ETL in the device, a high Vocof 1.18 V is achieved. It has been proven that the TiO2/SnO2 bilayer is a promising alternative ETL for high efficiency PSCs.

Inducing the SnO2-based electron transport layer into NiFe LDH/NF as efficient catalyst for OER and methanol oxidation reaction

In an electrocatalyst with a heterointerface structure,the different interfaces can efficiently adjust the catalyst’s conductivity and electron arrangement,thereby enhancing the activity of the electrocatalyst.Ultrathin and smaller Ni Fe LDH was successfully constructed on the surface of SnOnanosheet supported NF by layer by layer assembly,and exhibits lower overpotential of 234 mV at a current density of 10 m A cm,which only increases by 6.4%even at a high current density of 100 mA cm.The excellent OER activity of catalyst is attributed to the contribution of the semiconductor SnOelectron transport layer.Through experiments and characterization,3d structure SnOnanosheets control the growth of ultra-thin nickel-iron,the hierarchical interface between SnOand Ni Fe LDH can change the electron arrangement around the iron and nickel active centers at the interface,resulting the valence states of iron slightly increased and Nicontent increased.The result will promote the oxidation of water.Meanwhile,the SnOsemiconductor as electron transport layer is conducive to trapping electrons generated in oxidation reaction,promoting electrons transferring from the Ni Fe LDH active center to the Ni substrate more quickly,and enhance the activity of Ni Fe LDH.It also shows excellent activity in an electrolyte solution containing 0.5 M methanol and 1 M KOH,and only 1.396 V(vs.RHE)is required to drive a current density of 10 mA cm.

Chlorine-modified SnO2 electron transport layer for high-efficiency perovskite solar cells

A high-quality electron transport layer(ETL)is a critical component for the realization of high-efficiency perovskite solar cells.We developed a controllable direct-contact reaction process to prepare a chlorinated SnO2(SnO2-Cl)ETL.It is unique in that(a)102-dichlorobenzene is used to provide more reactive Cl radicals for more in-depth passivation;(b)it does not introduce any impurities other than chlorine.It is found that the chlorine modification significantly improves the electron extraction.Consequently,its associated solar cell efficiency is increased from 17.01%to 17.81%comparing to the pristine SnO2 ETL without the modification.The hysteresis index is significantly reduced to 0.017 for the SnO2-Cl ETL.

基于TiO2/Perovskite/P3HT结构的n-i-p型钙钛矿电池的电极界面优化与器件性能

以TiO_2/钙钛矿(PVSK)/P3HT的n-i-p型钙钛矿电池作为研究对象,研究了TiO_2薄膜退火温度对TiO_2薄膜的结晶性、基于此的钙钛矿薄膜的形貌以及光伏器件性能的影响,比较了P3HT的掺杂以及不同批次P3HT材料对钙钛矿太阳能电池器件性能的影响。结果表明:TiO_2薄膜的退火工艺及P3HT的批次对器件性能影响较大。TiO_2薄膜的制备工艺设为退火温度为300℃,退火时间为45min,提高TiO_2的退火温度到500℃,钙钛矿太阳能电池的效率可提高到11.27%.通过优化钙钛矿薄膜厚度为190nm,制备得到光电转换效率为6.77%的钙钛矿薄膜光伏电池。基于低温TiO_2为电子传输层、掺杂P3HT为空穴传输层的器件性能为开路电压VOC=0.98V,短路电流J_(SC)=19.94mA/cm^2,填充因子f_F=0.42,转换效率η(PCE)=8.18%.TiO_2电子传输层和P3HT空穴传输层的系统优化对制备高性能n-i-p结构钙钛矿电池具有重要意义。

ZnO/Cs_(2)CO_(3)双电子传输层有机太阳能电池

有机太阳能电池的异质结界面是影响其性能的一个重要因素.以氧化锌/碳酸铯作为双电子传输层,改善电子传输层与活性层的界面接触并提高电子传输能力.利用溶胶-凝胶法制备OSCs器件,通过优化的双电子传输层,使基于PTB7-Th:PC_(71)BM的OSCs器件的最高效率达到了8.08%,其相较于ZnO电子传输层器件提高了10.68%.实验表明,由于ZnO/Cs_(2)CO_(3) ETLs具有最佳的表面形貌和光吸收,其填充因子、短路电流密度和电子迁移率都显著提升.这种ZnO/Cs_(2)CO_(3)双电子传输层为OSCs性能改善提供了新的思路.

Solution-processed quantum dot SnO_(2) as an interfacial electron transporter for stable fully-air-fabricated metal-free perovskite solar cells

Perovskite solar cells could strongly compete with the silicon solar cells in the market soon as illustrated in recent studies.In this work,promising and stable metal-free perovskite solar cells(PSCs)has been successfully fabricated using an inorganic SnO_(2)/Quantum dot SnO_(2)(QD-SnO_(2))double layer as an efficient electron transport layer via a low-temperature solution process.The fully-air fabricated PSCs in the form of FTO/SnO_(2)/QD-SnO_(2)/CH3NH3PbI3/Carbon were tested at different annealed QD-SnO_(2) between 300 and 500℃.The as-prepared QD-SnO_(2) and the fabricated devices are characterized by various techniques,including XRD,XPS,HR-TEM,FE-SEM,UVeviseNIR spectroscopy,PL,and solar simulator.The prepared QD-SnO_(2) at 300℃ has shown well-ordered nanoparticles of 5.6 nm in diameter with superior carrier density(1.5×10^(15) cm^(-3))and highest carrier mobility(64.1 cm^(2)·V^(-1)·s^(-1)),accelerating the carriers separation process within the cell.The best devices demonstrated a maximum power conversion effi-ciency(PCE)of 11.7%,VOC 0.81 V,JSC 19.5 mA·cm^(-2),and FF 74%.The presence of an interfacial layer of QDSnO_(2) over the blocking SnO_(2) upsurges the band gaps alignment and accelerates the carriers extraction rate affecting the performance of the fabricated perovskite devices.Moreover,the optimized fabricated devices revealed a shelf stability-life of four months in humid air(40%-50%)with>83%of its initial PCE.This simple synthetic approach can develop the opportunities to transfer the cell from the lab to the market,which will be compatible with large-scale production.