Multistage interband cascade photovoltaic devices with a bandgap of 0.23 eV operating above room temperature

Interband cascade(IC)photovoltaic(PV)device structures,consisting of multiple discrete InAs/GaSb superlattice absorbers sandwiched between electron and hole barriers,were grown by molecular beam epitaxy.Details of the molecular beam epitaxy growth and material characterization of the structures are presented.The discrete absorber architecture enables certain advantages,such as high open-circuit voltage,high collection efficiency,high operating temperature,and smooth integration of cascade stages with different bandgaps.The two-and three-stage ICPV devices presented in this article operate at room temperature with substantial open-circuit voltages at a cutoff wavelength of 5.3 lm(corresponding to a bandgap of 0.23 eV),the longest ever reported for room temperature PV devices.The device characteristics indicate a high level of current matching and demonstrate the advantages of the interband cascade approach in thermophotovoltaic cell design.

Shape Control of Doped Semiconductor Nanocrystals (d-Dots)

Formation of Mn2+-doped ZnSe quantum dots(Mn:ZnSe d-dots)with both branched and nearly spherical shapes has been studied.Structure analysis indicates that the Mn2+dopants were localized in the core of a branched nanocrystal.The growth of branched d-dots,rather than spherical ones,was achieved by simply varying the concentration of two organic additives,fatty acids,and fatty amines.The photoluminescence properties of the branched nanocrystals were explored and compared with those of the nearly spherical particles.

Multimode vibrational strong coupling in direct laser written mid-IR plasmonic MIM nano-patch antennas

Strong coupling of mid-infrared(mid-IR)vibrational transitions to optical cavities provides a means to modify and control a material’s chemical reactivity and offers a foundation for novel chemical detection technology.Currently,the relatively large volumes of the mid-IR photonic cavities and weak oscillator strengths of vibrational transitions restrict vibrational strong coupling(VSC)studies and devices to large ensembles of molecules,thus representing a potential limitation of this nascent field.Here,we experimentally and theoretically investigate the mid-IR optical properties of 3D-printed multimode metal-insulator-metal(MIM)plasmonic nanoscale cavities for enabling strong light-matter interactions at a deep subwavelength regime.We observe strong vibration-plasmon coupling between the two dipolar modes of the L-shaped cavity and the carbonyl stretch vibrational transition of the polymer dielectric.The cavity mode volume is half the size of a typical square-shaped MIM geometry,thus enabling a reduction in the number of vibrational oscillators to achieve strong coupling.The resulting three polariton modes are well described by a fully coupled multimode oscillator model where all coupling potentials are non-zero.The 3D printing technique of the cavities is a highly accessible and versatile means of printing arbitrarily shaped submicron-sized mid-IR plasmonic cavities capable of producing strong light–matter interactions for a variety of photonic or photochemical applications.Specifically,similar MIM structures fabricated with nanoscopic voids within the insulator region could constitute a promising microfluidic plasmonic cavity device platform for applications in chemical sensing or photochemistry.

电阻式核磁共振测量的最新进展

电阻式核磁共振(RDNMR)测量是1988年由德国马普所的von Klitzing研究小组针对GaAs二维电子气中少量核自旋的探测而提出的一种具有超高灵敏度的实验技术.目前,RDNMR已经成为研究单层或双层GaAs二维电子气核自旋和电子自旋特性的重要手段.由于为实现电阻式核磁共振测量所建立的动态核极化方法强烈依赖于GaAs特有的材料属性,至今这一技术一直没有扩展应用到其他半导体低维系统中.最近,本研究小组发展了一种动态核极化新方法,成功实现了对典型窄带半导体锑化铟(InSb)二维电子气的电阻式核磁共振测量.本文在介绍电阻式核磁共振测量工作原理及已建立的典型动态核极化方法的基础上,着重讨论所提出的动态核极化新方法的机理、实验结果以及对今后研究的展望.