Name: recombination dynamics in thin-film photovoltaic materials via time-resolved microwave conductivity
Uploaded: 2017-03-06T13:00:00.000+00:00
Duration: 11 min 30 s
Description: Watch this Scientific Journal Video about Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity at JoVE.com

Acknowledgment is made to the Australian Research Council (LE130100146, DP160103008). JAG is supported via an Australian Postgraduate Award, and DRM by an ARC Future Fellowship (FT130100214). We thank Nikos Kopidakis for helpful discussions.

<ol>
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Lett. 1 (22), 3261-3265 (2010).</li><li>Colbeau-Justin, C., Valenzuela, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-resolved+microwave+conductivity+(TRMC)+a+useful+characterization+tool+for+charge+carrier+transfer+in+photocatalysis:+a+short+review.">Time-resolved microwave conductivity (TRMC) a useful characterization tool for charge carrier transfer in photocatalysis: a short review.</a> Revista mexicana de f&#237;sica. 59 (3), 191-200 (2013).</li><li>Luna, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synergetic+effect+of+Ni+and+Au+nanoparticles+synthesized+on+titania+particles+for+efficient+photocatalytic+hydrogen+production.">Synergetic effect of Ni and Au nanoparticles synthesized on titania particles for efficient photocatalytic hydrogen production.</a> Applied Catalysis B: Environmental. 191, 18-28 (2016).</li><li>Ferguson, A. J., Kopidakis, N., Shaheen, S. E., Rumbles, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quenching+of+excitons+by+holes+in+poly+(3-hexylthiophene)+films.">Quenching of excitons by holes in poly (3-hexylthiophene) films.</a> J. Phys. Chem. C. 112 (26), 9865-9871 (2008).</li><li>Ferguson, A. J., Kopidakis, N., Shaheen, S. 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C. 117 (46), 24085-24103 (2013).</li><li>Xiao, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient,+high+yield+perovskite+photovoltaic+devices+grown+by+interdiffusion+of+solution-processed+precursor+stacking+layers.">Efficient, high yield perovskite photovoltaic devices grown by interdiffusion of solution-processed precursor stacking layers.</a> Energy Environ. Sci. 7 (8), 2619-2623 (2014).</li><li>Infelta, P. P., De Haas, M. P., Warman, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+study+of+the+transient+conductivity+of+pulse+irradiated+dielectric+liquids+on+a+nanosecond+timescale+using+microwaves.">The study of the transient conductivity of pulse irradiated dielectric liquids on a nanosecond timescale using microwaves.</a> Radiat. Phys. Chem. 10 (5-6), 353-365 (1977).</li><li>Saeki, A., Seki, S., Sunagawa, T., Ushida, K., Tagawa, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Charge-carrier+dynamics+in+polythiophene+films+studied+by+in-situ+measurement+of+flash-photolysis+time-resolved+microwave+conductivity+(FP-TRMC)+and+transient+optical+spectroscopy+(TOS).">Charge-carrier dynamics in polythiophene films studied by in-situ measurement of flash-photolysis time-resolved microwave conductivity (FP-TRMC) and transient optical spectroscopy (TOS).</a> Philosophical Magazine. 86 (9), 1261-1276 (2006).</li><li>Choi, W., Miyakai, T., Sakurai, T., Saeki, A., Yokoyama, M., Seki, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-contact,+non-destructive,+quantitative+probing+of+interfacial+trap+sites+for+charge+carrier+transport+at+semiconductor-insulator+boundary.">Non-contact, non-destructive, quantitative probing of interfacial trap sites for charge carrier transport at semiconductor-insulator boundary.</a> Appl. 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The authors have nothing to disclose.

虽然TRMC技术可以提供丰富的光诱导左右电荷载体的动态信息，这是电导率的间接测量，因此护理需要解释结果时才能作出。所述TRMC技术测量总的移动性，并且不能用于电子和空穴的迁移率之间进行区分。其潜在的假定电导率正比于反射功率改变仅持有时变化小（&lt;5％）16。此外，如果衰变过程中的共振频率的移位很大，则总（复）电导率将不得不被解构成其实部和虚部可被分?...

闪光光解时间分辨微波电导率（FP-TRMC）监视在NS-微秒时间尺度光激发载流子的动态，使之成为研究载流子复合过程的理想工具。理解的光诱导电荷载体的衰变机制薄膜半导体是具有关键的重要性的范围内的应用，包括光电装置的优化。诱导载流子寿命往往诱发载流子密度，激发波长，流动性陷阱密度和叠印率的功能。本文演示了时间分辨微波电导率（TRMC）技术的通用性调查范围广泛的载体动态依赖（强度，波长，微波频率）及其解释。 光生电荷可以修改以使用实际和材料的介电常数的虚数部分，这取决于它们的流动性和degre<html>坐月子/本地化1电子。材料的导电性<img alt="方程" src="/files/ftp_upload/55232/55232eq1.jpg" />正比于其复数介电常数<img alt="方程" src="/files/ftp_upload/55232/55232eq2.jpg" />哪里<img alt="方程" src="/files/ftp_upload/55232/55232eq3.jpg" />是微波电场的频率， <img alt="方程" src="/files/ftp_upload/55232/55232eq4.jpg" />和<img alt="方程" src="/files/ftp_upload/55232/55232eq5.jpg" />是介电常数的实部和虚部。因此，导电性的实部相关介电常数的虚部，并且可以被映射到微波吸收，而导电性（以后称为极化）的虚部是与在谐振频率的偏移的微波场1。 t"的&gt; TRMC超过其它技术有几个优点。例如，直流光电导测量从一系列通过该接口在电极/材料接口从所述材料与电极接触而产生的增强的重组，背面的电荷注入并发症遭受，以及作为激子和成对对增强离解由于施加电压2都会导致所测量的载体迁移率和寿命的扭曲。相反，TRMC是无电极的技术，其测量载流子的固有流动性不会因充电触点间转移的扭曲。 利用微波功率，作为载流子动力学的探针的一个显著优点在于，以及监测的电荷载体，衰减机制衰减寿命/途径也可以被分析。 TRMC可以用来确定总的移动性3和生活荷载体的时间4。这些参数随后可用于直接和陷阱介导的重组机制3,5之间进行区分。这两个单独的衰减途径的依赖性可以定量分析作为载流子密度3,5和能量/波长5的功能。致载流子的本地化/约束可以通过比较电导率VS极化5（虚VS介电常数的实部）的衰变进行调查。 此外，也许是最重要的是，TRMC可用于表征其充当电荷载体衰减途径陷阱态。表面陷阱，例如，可从大容量陷阱由VS未钝化的样品6比较钝化区分开。亚带隙状态可以使用子带隙激发能5被直接影响。陷阱密度可以通过拟合TRMC数据7推断。 由于这种技术的通用性，TRMC已应用于研究广泛的材料，包括:传统的薄膜半导体如硅6,8和TiO 2 9，10，纳米粒子11，纳米管1中 ，有机半导体12，材料的共混物13，第 14，和混合光伏材料3，4，5。 为了获得使用TRMC定量信息，这是至关重要的，以便能够准确地确定数的吸收对于给定的光激发的光子。由于用于量化薄膜，纳米颗粒，溶液和不透明样品的吸收方法不同，这里介绍的样品制备和校准技术被用于薄膜样品而设计的。然而，提出了TRMC测量协议是很一般。

<table><tbody><tr><td>Hellmanex III detergent</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/sial/z805939?lang=en&amp;amp;region=AU</td><td>Z805939</td><td>Corrosive and toxic. See SDS.</td></tr><tr><td>Lead(II) iodide (99%)</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/aldrich/211168?lang=en&amp;amp;region=AU</td><td>211168</td><td>Toxic. See SDS.</td></tr><tr><td>Anhydrous dimethylformamide (99.8%)</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/sial/227056?lang=en&amp;amp;region=AU</td><td>227056</td><td>Toxic. See SDS.</td></tr><tr><td>Anhydrous dimethylsulfoxide (99.9%)</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/sial/276855?lang=en&amp;amp;region=AU</td><td>276855</td><td>Toxic. See SDS.</td></tr><tr><td>Anhydrous 2-Propanol (99.5%)</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/sial/278475?lang=en&amp;amp;region=AU&amp;amp;gclid=&lt;br/&gt; COnlgPaw780CFQZvvAod17EA4Q</td><td>278475</td><td></td></tr><tr><td>Methylammonium iodide</td><td>Dyesol&lt;br/&gt; www.dyesol.com/products/dsc-materials/perovskite-precursors/methylammonium-iodide.html</td><td>MS101000</td><td>Also sold by Sigma Aldrich</td></tr><tr><td>Poly(methyl methacrylate)</td><td>Sigma Aldrich</td><td>445746</td><td></td></tr><tr><td>Anhydrous chlorobenzene (99.8%)</td><td>Sigma Aldrich&lt;br/&gt; www.sigmaaldrich.com/catalog/product/aldrich/445746?lang=en&amp;amp;region=AU</td><td>284513</td><td>Toxic. See SDS.</td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Model&lt;/strong&gt;</td><td>&lt;strong&gt;Comments/Description&lt;/strong&gt;</td></tr><tr><td>UV-VIS-NIR spectrophotometer</td><td>Perkin-Elmer&amp;nbsp;</td><td>Lambda 900</td><td></td></tr><tr><td>Profilometer</td><td>Veeco</td><td>Dektak 150</td><td></td></tr><tr><td>Vector Network Analyzer</td><td>Keysight&lt;br/&gt; www.keysight.com/en/pdx-x201927-pn-N9918A/fieldfox-handheld-microwave-analyzer-265-ghz?cc=US&amp;amp;lc=eng</td><td>Fieldfox N9918A</td><td></td></tr><tr><td>Tunable wavelength laser</td><td>Opotek&lt;br/&gt; www.opotek.com/product/opolette-355</td><td>Opolette 355</td><td></td></tr><tr><td>Neutral density filters</td><td>Thorlabs&lt;br/&gt; www.thorlabs.hk/newgrouppage9.cfm?objectgroup_id=3193</td><td>NUK01</td><td></td></tr><tr><td>Power meter</td><td>Thorlabs&lt;br/&gt; www.thorlabs.com/thorproduct.cfm?partnumber=PM100D</td><td>PM100D</td><td></td></tr><tr><td>Power sensor</td><td>Thorlabs&lt;br/&gt; www.thorlabs.com/thorproduct.cfm?partnumber=S401C</td><td>S401C</td><td></td></tr><tr><td>Cavity</td><td>Custom built</td><td></td><td>The cavity used in for this experiment was designed and built in-house.</td></tr></tbody></table>

recombination dynamics in thin-film photovoltaic materials via time-resolved microwave conductivity

提出了一种用于研究在薄膜半导体光生电荷载体，特别是在光生伏打材料，如有机铅卤化物钙钛矿的重组动力学方法。钙钛矿薄膜的厚度和吸收系数最初特征在于轮廓和UV-VIS吸收光谱。两个激光功率和腔灵敏度的校准进行详细说明。一种用于执行闪光光解时间分辨微波电导率（TRMC）实验协议，确定材料的导电性的非接触方法，提出。一种用于通过执行TRMC微波频率的函数识别所述复合电导率的实部和虚部处理中给出。载流子动力学在不同的激励机制（包括功率和波长）决定。直接和陷阱介导的衰变过程区分技术进行介绍和讨论。结果被建模并且参考解释为在一个半导体光生电荷载体的一般动力学模型。所描述的技术适用于广泛的光电子材料，包括有机和无机光伏材料，纳米粒子，和导电/半导电薄膜。

这里提出的代表性结果，从一个250纳米CH 3 NH 3碘化铅3薄膜样品获得。 导电性的动力学<img alt="方程" src="/files/ftp_upload/55232/55232eq54.jpg" />可以与电荷载体的动态<img alt="方程" src="/files/ftp_upload/55232/55232eq55.jpg" />通过<img alt="方程" src="/files/ftp_upload/55232/55232eq56.jpg"...

Watch this Scientific Journal Video about Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity at JoVE.com

Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

通过时间分辨微波电导率重组动力学薄膜光伏材料

A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials ...

recombination-dynamics-thin-film-photovoltaic-materials-via-time

Universidad San Sebastian

Research

JoVE Journal

Engineering

11.6K 次观看.  ARC Centre of Excellence in Exciton Science. A Time Resolved Microwave Conductivity technique for investigating direct and trap-mediated recombination dynamics and determining carrier mobilities of thin film semiconductors is presented here.

视频: Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity

Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

并行定量的导电性和力学性能测试的有机光伏材料利用原子力显微镜

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

科研

工程学

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, spin-flip scattering) is described, using experiments on GaMnAs as a prototype III-Mn-V system.&#160; Spectrally-resolved and time-resolved experimental configurations are described, including the use of zero-background autocorrelation techniques for pulse optimization.&#160; The etching process used to prepare GaMnAs samples for four-wave mixing experiments is also highlighted.&#160; The high temporal resolution of this technique, afforded by the use of short (20 fsec) optical pulses, permits the rapid spin-flip scattering process in this system to be studied directly in the time domain, providing new insight into the strong exchange coupling responsible for carrier-mediated ferromagnetism.&#160; We also show that spectral resolution of the four-wave mixing signal allows one to extract clear signatures of (s,p)-d hybridization in this system, unlike linear spectroscopy techniques.&#160;&#160; This increased sensitivity is due to the nonlinearity of the technique, which suppresses defect-related contributions to the optical response. This method may be used to measure the time scale for coherence decay (tied to the fastest scattering processes) in a wide variety of semiconductor systems of interest for next generation electronics and optoelectronics.

The technique of femtosecond four-wave mixing is described, including spectrally-resolved and time-resolved configurations. We illustrate the utility of this technique for the investigation of crucial physical properties in the III-V diluted magnetic semiconductors, afforded by its nonlinearity and high temporal resolution.

The application of femtosecond four-wave mixing to the study of fundamental properties of diluted magnetic semiconductors ((s,p)-d hybridization, ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

使用中子自旋回声解决放牧发生率散射调查有机太阳能电池材料

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

利用微波和电介质固体的宏观样本，研究无序光子带隙材料的光子特性

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm2. Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.

Tin sulfide (SnS) is a candidate material for Earth-abundant, non-toxic solar cells. Here, we demonstrate the fabrication procedure of the SnS solar cells employing atomic layer deposition, which yields 4.36% certified power conversion efficiency, and thermal evaporation which yields 3.88%.

通过热蒸发和原子层沉积使记录效率的SnS太阳能电池

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent ...

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

The optical, electrical, and structural properties of dislocations and of grain boundaries in semiconductor materials can be determined by experiments performed in a scanning electron microscope. Electron microscopy has been used to investigate cathodoluminescence, electron beam induced current, and diffraction of backscattered electrons.

通过扫描电子显微镜在半导体材料的扩展缺陷的全面表征

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications ...

Fabrication of Fully Solution Processed Inorganic Nanocrystal Photovoltaic Devices

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal inks. For the photoactive absorber layer, colloidal CdTe and CdSe nanocrystals (3-5 nm) are synthesized using an inert hot injection technique and cleaned with precipitations to remove excess starting reagents. Similarly, gold nanocrystals (3-5 nm) are synthesized under ambient conditions and dissolved in organic solvents. In addition, precursor solutions for transparent conductive indium tin oxide (ITO) films are prepared from solutions of indium and tin salts paired with a reactive oxidizer. Layer-by-layer, these solutions are deposited onto a glass substrate following annealing (200-400 &#176;C) to build the nanocrystal solar cell (glass/ITO/CdSe/CdTe/Au). Pre-annealing ligand exchange is required for CdSe and CdTe nanocrystals where films are dipped in NH4Cl:methanol to replace long-chain native ligands with small inorganic Cl- anions. NH4Cl(s) was found to act as a catalyst for the sintering reaction (as a non-toxic alternative to the conventional CdCl2(s) treatment) leading to grain growth (136&#177;39 nm) during heating. The thickness and roughness of the prepared films are characterized with SEM and optical profilometry. FTIR is used to determine the degree of ligand exchange prior to sintering, and XRD is used to verify the crystallinity and phase of each material. UV/Vis spectra show high visible light transmission through the ITO layer and a red shift in the absorbance of the cadmium chalcogenide nanocrystals after thermal annealing. Current-voltage curves of completed devices are measured under simulated one sun illumination. Small differences in deposition techniques and reagents employed during ligand exchange have been shown to have a profound influence on the device properties. Here, we examine the effects of chemical (sintering and ligand exchange agents) and physical treatments (solution concentration, spray-pressure, annealing time and annealing temperature) on photovoltaic device performance.

This protocol describes the synthesis and solution deposition of inorganic nanocrystals layer by layer to produce thin film electronics on non-conductive surfaces. Solvent-stabilized inks can produce complete photovoltaic devices on glass substrates via spin and spray coating following post-deposition ligand exchange and sintering.

全面解决方案处理的无机纳米晶体光伏器件的制造

We demonstrate a method for the preparation of fully solution processed inorganic solar cells from a spin and spray coating deposition of nanocrystal ...

Influence of Hybrid Perovskite Fabrication Methods on Film Formation, Electronic Structure, and Solar Cell Performance

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to achieve device efficiencies exceeding other thin film device technologies. Yet, large variations in device efficiency and basic physical properties are reported. This is due to unintentional variations during film processing, which have not been sufficiently investigated so far. We therefore conducted an extensive study of the morphology and electronic structure of a large number of CH3NH3PbI3 perovskite where we show how the preparation method as well as the mixing ratio of educts methylammonium iodide and lead(II) iodide impact properties like film formation, crystal structure, density of states, energy levels, and ultimately the solar cell performance.

We present an extensive study on the effects of different fabrication methods for organic/inorganic perovskite thin films by comparing crystal structures, density of states, energy levels, and ultimately the solar cell performance.

上成膜钙钛矿型混合制造方法，电子结构和太阳能电池性能的影响

Hybrid organic/inorganic halide perovskites have lately been a topic of great interest in the field of solar cell applications, with the potential to ...

化学

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational spectroscopy and time-resolved electron diffraction. Liquid crystal phase is an important state of matter that exists between the solid and liquid phases and it is common in natural systems as well as in organic electronics. Liquid crystals are orientationally ordered but loosely packed, and therefore, the internal conformations and alignments of the molecular components of LCs can be modified by external stimuli. Although advanced time-resolved diffraction techniques have revealed picosecond-scale molecular dynamics of single crystals and polycrystals, direct observations of packing structures and ultrafast dynamics of soft materials have been hampered by blurry diffraction patterns. Here, we report time-resolved IR vibrational spectroscopy and electron diffractometry to acquire ultrafast snapshots of a columnar LC material bearing a photoactive core moiety. Differential-detection analyses of the combination of time-resolved IR vibrational spectroscopy and electron diffraction are powerful tools for characterizing structures and photoinduced dynamics of soft materials.

Here, we present the protocols of differential-detection analyses of time-resolved infrared vibrational spectroscopy and electron diffraction which enable observations of the deformations of local structures around photoexcited molecules in a columnar liquid crystal, giving an atomic perspective on the relationship between the structure and the dynamics of this photoactive material.

观测 Photoresponsive 液晶结构动力学的新方法

We discuss in this article the experimental measurements of the molecules in liquid crystal (LC) phase using the time-resolved infrared (IR) vibrational ...

Carrier Lifetime Measurements in Semiconductors through the Microwave Photoconductivity Decay Method

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor materials, especially SiC. In principle, excess carriers in the semiconductor generated via excitation recombine with time and, subsequently, return to the equilibrium state. The time constant of this recombination is known as the carrier lifetime, an important parameter in semiconductor materials and devices that requires a noncontact and nondestructive measurement ideally achieved by the &#956;-PCD. During irradiation of a sample, a part of the microwave is reflected by the semiconductor sample. Microwave reflectance depends on the sample conductivity, which is attributed to the carriers. Therefore, the time decay of excess carriers can be observed through detection of the reflected microwave intensity, whose decay curve can be analyzed for estimation of the carrier lifetime. Results confirm the suitability of the &#956;-PCD protocol in measuring the carrier lifetime in semiconductor materials and devices.

As one of the important physical parameters in semiconductors, carrier lifetime is measured herein via a protocol employing the microwave photoconductivity decay method.

微波导光衰减法测量半导体中的载波寿命

This work presents a protocol employing the microwave photoconductivity decay (&#956;-PCD) for measurement of the carrier lifetime in semiconductor ...