Lead-free hybrid perovskites for photovoltaics

• Oleksandr Stroyuk

Beilstein J. Nanotechnol. 2018, 9, 2209–2235, doi:10.3762/bjnano.9.207

• market is dominated by silicon solar cells with top light-to-current conversion efficiencies reaching ≈27% [1]. As an alternative to the Si-based cells requiring a relatively thick absorber layer due to the indirect character of electron transitions in Si, direct-bandgap metal chalcogenide semiconductors

• + cations Hybrid perovskites with partially substituted lead ions Using a small “tool kit” of two metals, Sn and Pb, and two organic cations, A = MA and FA, a broad variety of isostructural Pb-, Sn- and Pb–Sn-based ASnxPb1−xI3 HPs can be synthesized with a bandgap varying from 1.25 to 1.75 eV depending on

• the HP composition [92]. By simultaneously tuning the composition of Pb–Sn and halide components, a solar light absorber was designed with a bandgap of 1.35 eV ideal for the solar light harvesting. The inverted cells based on MAPb0.5Sn0.5(I0.8Br0.2)3 demonstrated PCEs of up to 17.63% [70]. A

Spin-coated planar Sb₂S₃ hybrid solar cells approaching 5% efficiency

• Pascal Kaienburg,
• Benjamin Klingebiel and
• Thomas Kirchartz

Beilstein J. Nanotechnol. 2018, 9, 2114–2124, doi:10.3762/bjnano.9.200

• routes based on different precursors reported in the literature. By studying the film morphology, sub-bandgap absorption and solar cell performance, improved annealing procedures are found and the crystallization temperature is shown to be critical. In order to determine the optimized processing

• -bandgap region [53][54][55][56] including band tails that yield the Urbach energy as a measure of disorder as well as the detection of (optically active) defects in the band gap which can act as recombination centers in a solar cell. The Sb-TU process shows a slight increase in uncovered substrate area

• attributed to interference in the smooth films – which did not fully cancel out during data analysis – instead of actual variations in the materials’ density of states in the sub-bandgap region. The negative impact of the increased defect density on device performance is confirmed by comparing solar cells

Improving the catalytic activity for hydrogen evolution of monolayered SnSe_2(1−x)S_2x by mechanical strain

• Sha Dong and
• Zhiguo Wang

Beilstein J. Nanotechnol. 2018, 9, 1820–1827, doi:10.3762/bjnano.9.173

• ][33][34][35][36][37]. For example, Komsa et al. [34] have investigated the electronic properties of monolayer MoS2xSe2(1−x) and found that the bandgaps can be continuously tuned with the variation of Se composition. Liu et al. [38] have studied Mo1−xWxS2 and observed variations of the direct bandgap

• ] and agrees well with previous results [36]. SnS2 and SnSe2 monolayers are indirect-bandgap semiconductors, as highlighted in their band structures shown in Figure 1e and Figure 1i, respectively. The valence-band maximum (VBM) is located at the M-point, whereas the conduction-band minimum (CBM) is

• , Figure 1g and Figure 1h, respectively. The substitution of S with Se does not affect the indirect bandgap semiconducting characteristics; however, the band gap is tuned with changing the content of Se, as shown in Figure 1d with the indirect band gap decreasing with increasing Se content. These results

Multimodal noncontact atomic force microscopy and Kelvin probe force microscopy investigations of organolead tribromide perovskite single crystals

• Yann Almadori,
• David Moerman,
• Jaume Llacer Martinez,
• Philippe Leclère and
• Benjamin Grévin

Beilstein J. Nanotechnol. 2018, 9, 1695–1704, doi:10.3762/bjnano.9.161

• shifts are observed when the wavelength falls below the MAPbBr3 bandgap (EG ≈ 2.2eV [12]). This confirms that the measured height changes originate from the intrinsic photostriction of the MAPbBr3 crystal. However, an almost identical photoresponse is observed under 405 nm and 515 nm illumination, which

• seems different from the case of MAPbI3 (for which a wavelength-dependent photostriction was observed [16] above the bandgap). Here, it is noteworthy that the wavelength of our green laser falls within an absorption peak due to a strong excitonic transition [24][25]. Further measurements at intermediate

• wavelengths (currently unavailable in our setup) would be necessary to draw a definitive conclusion about the wavelength dependency of the photoresponse above the bandgap. The fast surface photovoltage polarity implies that negative charges accumulate quickly under illumination beneath the surface of the

Absence of free carriers in silicon nanocrystals grown from phosphorus- and boron-doped silicon-rich oxide and oxynitride

• Daniel Hiller,
• Julian López-Vidrier,
• Keita Nomoto,
• Michael Wahl,
• Wolfgang Bock,
• Tomáš Chlouba,
• František Trojánek,
• Sebastian Gutsch,
• Margit Zacharias,
• Dirk König,
• Petr Malý and
• Michael Kopnarski

Beilstein J. Nanotechnol. 2018, 9, 1501–1511, doi:10.3762/bjnano.9.141

• concentration of a semiconductor can be controlled via doping. Conventional impurity doping requires the incorporation of a suitable foreign atom on a lattice site and its ionization by thermal energy. Therefore, the energetic position of a dopant in the bandgap has to be close to the respective band edges. For

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

• Rashmi Acharya,
• Brundabana Naik and
• Kulamani Parida

Beilstein J. Nanotechnol. 2018, 9, 1448–1470, doi:10.3762/bjnano.9.137

Robust midgap states in band-inverted junctions under electric and magnetic fields

• Álvaro Díaz-Fernández,
• Natalia del Valle and
• Francisco Domínguez-Adame

Beilstein J. Nanotechnol. 2018, 9, 1405–1413, doi:10.3762/bjnano.9.133

• spinful two-band model that is equivalent to the Dirac model for relativistic electrons. The mass term is half the bandgap and changes its sign across the junction. For the sake of algebraic simplicity, we assumed same-sized and aligned gaps, although this is not a serious limitation to the validity of

Ag₂WO₄ nanorods decorated with AgI nanoparticles: Novel and efficient visible-light-driven photocatalysts for the degradation of water pollutants

• Shijie Li,
• Shiwei Hu,
• Wei Jiang,
• Yanping Liu,
• Yu Liu,
• Yingtang Zhou,
• Liuye Mo and
• Jianshe Liu

Beilstein J. Nanotechnol. 2018, 9, 1308–1316, doi:10.3762/bjnano.9.123

• photocatalytic performance for dye degradation under light irradiation [30][31][36][37]. Unfortunately, due to its wide bandgap of about 3.1 eV, Ag2WO4 has limited photocatalytic activity under sunlight, which severely limits its application and illustrates the urgency for optimization of Ag2WO4 to overcome

• these disadvantages [38][39][40][41][42]. The integration of VLD components with wide bandgap semiconductors having well-matched energy bands has provided a new opportunity for the development of VLD photocatalysts [12]. As a consequence, some Ag2WO4-based composites containing VLD components such as

Computational exploration of two-dimensional silicon diarsenide and germanium arsenide for photovoltaic applications

• Sri Kasi Matta,
• Chunmei Zhang,
• Yalong Jiao,
• Anthony O'Mullane and
• Aijun Du

Beilstein J. Nanotechnol. 2018, 9, 1247–1253, doi:10.3762/bjnano.9.116

• dynamic stability of the compounds, which is inferred by analyzing their vibrational normal mode. SiAs2 and GeAs2 monolayers possess a bandgap of 1.91 and 1.64 eV, respectively, which is excellent for sunlight harvesting, while the exciton binding energy is found to be 0.25 and 0.14 eV, respectively

Room-temperature single-photon emitters in titanium dioxide optical defects

• Kelvin Chung,
• Yu H. Leung,
• Chap H. To,
• Aleksandra B. Djurišić and
• Snjezana Tomljenovic-Hanic

Beilstein J. Nanotechnol. 2018, 9, 1085–1094, doi:10.3762/bjnano.9.100

• -photon source within a wide bandgap semiconductor. Keywords: fluorescence; optical defects; room temperature; single-photon emitters; titanium dioxide; Introduction Single-photon sources offer non-classical states of light [1] and are a prerequisite for future quantum technologies [2]. There are many

• types of single-photon emitters that include molecules [3], trapped atoms [4], quantum dots [5] and defects in diamond [6]. More recently point defects of wide-bandgap semiconductors, such as zinc oxide (ZnO) [7][8][9] and silicon carbide [10], were shown to exhibit room-temperature single-photon

• emission. ZnO is the only metal oxide reported to host single-photon emitting defects at room temperature and was recently shown to exhibit stable fluorescence when uptaken into skin cells, making it a viable biomarker [11]. Titanium dioxide (TiO2) is a well-studied wide-bandgap semiconductor, its

Valley-selective directional emission from a transition-metal dichalcogenide monolayer mediated by a plasmonic nanoantenna

• Haitao Chen,
• Mingkai Liu,
• Lei Xu and
• Dragomir N. Neshev

Beilstein J. Nanotechnol. 2018, 9, 780–788, doi:10.3762/bjnano.9.71

• [6][7][8][9][10]. In particular, monolayer TMDCs with direct bandgap at the K and K′ points [11] make it possible to control the valley degree freedom entirely optically. Optical pumping of excitons of a specific valley polarization has been demonstrated by polarization-resolved photoluminescence (PL

Perovskite-structured CaTiO₃ coupled with g-C₃N₄ as a heterojunction photocatalyst for organic pollutant degradation

• Ashish Kumar,
• Christian Schuerings,
• Suneel Kumar,
• Ajay Kumar and
• Venkata Krishnan

Beilstein J. Nanotechnol. 2018, 9, 671–685, doi:10.3762/bjnano.9.62

• (VB) and conduction band (CB) edge potentials of g-C3N4 and CT can be calculated by using following equations [36][54]: where EVB and ECB are the VB and CB edge potentials and Eg is the bandgap of the semiconductor materials. The band gap values for g-C3N4 and CT are 2.75 eV and 3.45 eV respectively

Fabrication and photoactivity of ionic liquid–TiO₂ structures for efficient visible-light-induced photocatalytic decomposition of organic pollutants in aqueous phase

• Anna Gołąbiewska,
• Marta Paszkiewicz-Gawron,
• Aleksandra Sadzińska,
• Wojciech Lisowski,
• Ewelina Grabowska,
• Adriana Zaleska-Medynska and
• Justyna Łuczak

Beilstein J. Nanotechnol. 2018, 9, 580–590, doi:10.3762/bjnano.9.54

• diffuse reflection (DR)/UV–vis spectra of the photocatalysts as well as for the pure ionic liquids used in this study are shown in Figure 4. The pristine TiO2 obtained by the solvothermal method showed the expected bandgap of 3.2 eV and very weak visible-light absorption. However, the visible-light

High-contrast and reversible scattering switching via hybrid metal-dielectric metasurfaces

• Jonathan Ward,
• Khosro Zangeneh Kamali,
• Lei Xu,
• Guoquan Zhang,
• Andrey E. Miroshnichenko and
• Mohsen Rahmani

Beilstein J. Nanotechnol. 2018, 9, 460–467, doi:10.3762/bjnano.9.44

• metasurface. The geometrical parameters are Lx = 100 nm, Ly = 600 nm, Lz = 200 nm, t = 200 nm, d = 400 nm, h = 400 nm, g = 60 nm, p1 = 850 nm, p2 = 850 nm. (a) Bandgap energy (blue curve) and variation of refractive index (dark curve) versus temperature change for bulk silicon [40]. (b) Transmission of

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

• Liga Jasulaneca,
• Jelena Kosmaca,
• Raimonds Meija,
• Jana Andzane and
• Donats Erts

Beilstein J. Nanotechnol. 2018, 9, 271–300, doi:10.3762/bjnano.9.29

• Si. SiC is a wide bandgap (2.4–3.3 eV) semiconductor with a bulk Young’s modulus of 400–500 GPa [136] and high thermal conductivity on the order of 330 W∙m−1∙K−1 for bulk 3C–SiC [137], a larger than 1 MV cm−1 breakdown electric field as well as a high melting temperature. Regarding its elastic

Bombyx mori silk/titania/gold hybrid materials for photocatalytic water splitting: combining renewable raw materials with clean fuels

• Stefanie Krüger,
• Michael Schwarze,
• Otto Baumann,
• Christina Günter,
• Michael Bruns,
• Christian Kübel,
• Dorothée Vinga Szabó,
• Rafael Meinusch,
• Verónica de Zea Bermudez and
• Andreas Taubert

Beilstein J. Nanotechnol. 2018, 9, 187–204, doi:10.3762/bjnano.9.21

• to a wealth of studies on photocatalytic water splitting [6][7][8][9][10]. To be successful, the water splitting catalyst needs to have a certain set of properties. Most prominently, it should have a bandgap of at least 1.23 eV to provide the energy needed to split water. However, the bandgap should

• not exceed ca. 3 eV to most efficiently use the visible spectral range of the sunlight [6]. As a result, numerous water-splitting catalysts with various efficiencies have been reported [6][7][8][11][12][13]. Because of its bandgap of 3.0–3.2 eV (depending on the crystal structure and particle size [14

• bandgap of the TiO2 semiconductors [21]. Gallo et al. used amorphous TiO2 doped with Au and/or platinum (Pt) NPs to split water under ultraviolet (UV)-A light and simulated sunlight. Best results with 1.6 mmol/(h·g) of H2 production were obtained with Au0.5Pt0.5/TiO2 catalysts [22]. Chen et al. used

Design of photonic microcavities in hexagonal boron nitride

• Sejeong Kim,
• Milos Toth and
• Igor Aharonovich

Beilstein J. Nanotechnol. 2018, 9, 102–108, doi:10.3762/bjnano.9.12

• attractive candidate for a monolithic cavity system. In particular, hBN has a wide bandgap of ≈6 eV which makes it transparent in the visible spectral range that contains the zero phonon lines (ZPLs) of a range of ultra-bright emitters [21]. Furthermore, hBN has properties which are desirable for micro

• full photonic bandgap between the first and the second lowest photonic energy bands even when the effective index contrast is low [31]. The combination of a high Q-factor and a low refractive index enables a broad range of applications such as flexible photonic crystal devices and high figure of merit

Review on optofluidic microreactors for artificial photosynthesis

• Xiaowen Huang,
• Jianchun Wang,
• Tenghao Li,
• Jianmei Wang,
• Min Xu,
• Weixing Yu,
• Abdel El Abed and
• Xuming Zhang

Beilstein J. Nanotechnol. 2018, 9, 30–41, doi:10.3762/bjnano.9.5

• energy could be offered by external light. In principle, a semiconductor photocatalyst (e.g., TiO2, C3N4) absorbs the appropriate photon (hν ≥ E0, where E0 is the bandgap of the semiconductor photocatalyst) to excite an electron in the conduction band, leaving a hole in the valence band. The electron

Thermo- and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles

• Agata Siarkowska,
• Miłosz Chychłowski,
• Daniel Budaszewski,
• Bartłomiej Jankiewicz,
• Bartosz Bartosewicz and
• Tomasz R. Woliński

Beilstein J. Nanotechnol. 2017, 8, 2790–2801, doi:10.3762/bjnano.8.278

• PLCF with a Ti-doped 5CB nematic LC has been recently reported in [18], where a noticeable difference in both the orientation of the molecules and the propagation spectra of the PLCF was observed. The light was guided according to a mechanism known as the photonic bandgap (PBG) effect, in which only

Facile synthesis of silver/silver thiocyanate (Ag@AgSCN) plasmonic nanostructures with enhanced photocatalytic performance

• Xinfu Zhao,
• Dairong Chen,
• Abdul Qayum,
• Bo Chen and
• Xiuling Jiao

Beilstein J. Nanotechnol. 2017, 8, 2781–2789, doi:10.3762/bjnano.8.277

• catalyst due to its wide bandgap of 3.2 eV, which limits its practical application. Therefore, the development of new photocatalysts with visible-light catalytic performance, high surface active sites and long life of separated electron and hole pairs, has become a hot research topic in recent years. Ag

• importance. As one of the Ag-containing semiconductor materials, AgSCN exhibits superior stability under irradiation [23][24]. The relatively large bandgap of AgSCN (3.4 eV) makes it only ultraviolet light active, largely limiting the wide utilization of the solar light energy spectrum. The addition of Ag on

• absorption of Ag@AgSCN in both the UV and visible region, which is beneficial for application as a visible-light catalyst. The bandgap of AgSCN can be determined according to the Kubelka–Munk equation, which is estimated as 3.4 eV for sample M0 (Figure 2b), and the valence band value of 1.12 eV is obtained

CdSe nanorod/TiO₂ nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity

• Fakher Laatar,
• Hatem Moussa,
• Halima Alem,
• Lavinia Balan,
• Emilien Girot,
• Ghouti Medjahdi,
• Hatem Ezzaouia and
• Raphaël Schneider

Beilstein J. Nanotechnol. 2017, 8, 2741–2752, doi:10.3762/bjnano.8.273

• the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO2 composites until ≈725 nm. The CdSe (2 wt %)/TiO2 composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The

• suffers from two main drawbacks. First, due to its wide bandgap (Eg = 3.2 and 3.0 eV for anatase and rutile, respectively), TiO2 can only be activated by light with a wavelength of less than 390 nm to trigger the electron–hole separation. Second, TiO2 exhibits a low quantum efficiency due to the fast

• recombination of photogenerated charge carriers (electrons and holes). To address these problems, a number of studies have been devoted to the improvement of light absorption and charge separation by hybridizing TiO2 with narrow bandgap semiconductors, doping with metal or nonmetal elements, association with

Ab initio study of adsorption and diffusion of lithium on transition metal dichalcogenide monolayers

• Xiaoli Sun and
• Zhiguo Wang

Beilstein J. Nanotechnol. 2017, 8, 2711–2718, doi:10.3762/bjnano.8.270

• in the 1T or 1T' phase, but only a few of them were stable in both 2H/1T or 2H/1T' phases. The results show that lithium is energetically favourable for adsorption on MX2 monolayers, which can be semiconductors with a narrow bandgap and metallic materials. Lithium cannot be adsorbed onto 2H-WS2 and

• group VI for a given element M. The variation can be explained by the increasing atomic radius of elements X from S to Te. The band structures of MX2 monolayers in the stable phase are shown in Figure 2. The MX2 monolayers can be semiconducting with a direct and indirect bandgap or metallic materials

• , 1T-ZrX2 and 1T-HfX2 show semiconducting and metallic behaviour with X = S/Se and X = Te, respectively. 1T'-VTe2 and 1T'-MoTe2 show metallic behaviour and 1T'-WTe2 has a narrow bandgap of 0.50 eV. The obtained bandgap values are close to those previously reported for TiS2 [32], CrTe2 [40], TiX2 [32

Enhanced photoelectrochemical water splitting performance using morphology-controlled BiVO₄ with W doping

• Xin Zhao and
• Zhong Chen

Beilstein J. Nanotechnol. 2017, 8, 2640–2647, doi:10.3762/bjnano.8.264

• . Photoelectrochemical (PEC) water splitting generates hydrogen through chemical reactions assisted by photo-generated electrons and holes in semiconductor materials [1][2][3]. An ideal semiconductor for PEC water splitting requires a small bandgap to capture enough solar light, a high conversion efficiency, a good

• developing photoanode materials and optimizing their performance. Monoclinic BiVO4 is one of the most promising photoanode materials for PEC water splitting, as it meets most of the requirements. It has a theoretical conversion efficiency of 9.1% with a bandgap of 2.4 eV. Moreover, it also possesses a

Optical contrast and refractive index of natural van der Waals heterostructure nanosheets of franckeite

• Patricia Gant,
• Foad Ghasemi,
• David Maeso,
• Carmen Munuera,
• Elena López-Elvira,
• Riccardo Frisenda,
• David Pérez De Lara,
• Gabino Rubio-Bollinger,
• Mar Garcia-Hernandez and
• Andres Castellanos-Gomez

Beilstein J. Nanotechnol. 2017, 8, 2357–2362, doi:10.3762/bjnano.8.235

• bandgap (below 0.7 eV) and p-type doping, and that they are very resilient upon atmospheric exposure. These characteristics makes franckeite an excellent alternative to black phosphorus which tends to degrade quickly upon air exposure [20][21][22][23]. Here we study the thickness dependence of the optical

Substrate and Mg doping effects in GaAs nanowires

• Perumal Kannappan,
• Nabiha Ben Sedrine,
• Jennifer P. Teixeira,
• Maria R. Soares,
• Bruno P. Falcão,
• Maria R. Correia,
• Nestor Cifuentes,
• Emilson R. Viana,
• Marcus V. B. Moreira,
• Geraldo M. Ribeiro,
• Alfredo G. de Oliveira,
• Juan C. González and
• Joaquim P. Leitão

Beilstein J. Nanotechnol. 2017, 8, 2126–2138, doi:10.3762/bjnano.8.212

• for application in solar cells owing to their high absorption, direct bandgap, high carrier mobility and well-developed synthesis techniques [5][6][7][8][9]. Among the group III–V semiconductors, GaAs is one of the most intensively studied materials and has a suitable bandgap energy value for solar

• phase is favored [2]. In general, GaAs nanowires show a polytypic structure along the gowth axis that is characterized by the occurrence of a mixture of WZ and ZB phases [12][13][14]. This fact creates an unintentional bandgap that critically influences the optical and electrical properties of the

• level structure of the nanowires, a detailed investigation on the temperature-dependent PL is required. Before the presentation of the results, we will mention briefly the common temperature dependence of the bandgap in a semiconductor. As the temperature increases, the thermal expansion coefficient of