Silicon and germanium nanocrystals: properties and characterization

• Ivana Capan,
• Alexandra Carvalho and
• José Coutinho

Beilstein J. Nanotechnol. 2014, 5, 1787–1794, doi:10.3762/bjnano.5.189

• breakthroughs in photovoltaics. It is believed that quantum dot (QD) solar cells have the potential to reach a maximum conversion efficiency of about 66% [2]. A colloidal nanocrystal solar cell, which combines all the advantages of organics (scalable and controllable synthesis) with transport properties

Growth evolution and phase transition from chalcocite to digenite in nanocrystalline copper sulfide: Morphological, optical and electrical properties

• Priscilla Vasthi Quintana-Ramirez,
• Ma. Concepción Arenas-Arrocena,
• José Santos-Cruz,
• Marina Vega-González,
• Omar Martínez-Alvarez,
• Víctor Manuel Castaño-Meneses,
• Laura Susana Acosta-Torres and
• Javier de la Fuente-Hernández

Beilstein J. Nanotechnol. 2014, 5, 1542–1552, doi:10.3762/bjnano.5.166

• solar cell applications. In Table 2 we observe a clear decrease of Eg from 1.87 to 1.60 eV from crystalline chalcocite to the digenite phase, which is in agreement to the increasing crystal size observed with TEM. These values are slightly smaller to those reported for bulk copper sulfide (1.7 and 2.0

An insight into the mechanism of charge-transfer of hybrid polymer:ternary/quaternary chalcopyrite colloidal nanocrystals

• Parul Chawla,
• Son Singh and
• Shailesh Narain Sharma

Beilstein J. Nanotechnol. 2014, 5, 1235–1244, doi:10.3762/bjnano.5.137

• photovoltaics [5][6]. To this day, numerous inorganic semiconductors such as ZnO, TiO2, CdSe, CdS, PbSe and PbS have been studied. Particular focus has been put on the investigation of selenides or sulfides in conjunction with organic polymers (MEH-PPV, P3HT) for hybrid solar cell applications [6][7]. However

• , the toxicity and hazardous issues of inorganic materials, in particular of Cd and Pb, poses a serious threat to the environment. This has limited the realization of hybrid solar cell systems for commercialization [7]. On the other hand, copper indium diselenide (CISe) and related materials in

• displays similar structure and optical properties to CISe. In order to achieve an efficient hybrid solar cell performance, it is imperative to control the morphology of both organic and inorganic components without any phase separation at macroscopic scale. The implementation of such a control of the

Organic and inorganic–organic thin film structures by molecular layer deposition: A review

• Pia Sundberg and
• Maarit Karppinen

Beilstein J. Nanotechnol. 2014, 5, 1104–1136, doi:10.3762/bjnano.5.123

• films include optoelectronic devices, sensors, flexible electronics, solar cell applications, and protective coatings, to name only a few. It is also straightforward to make porous structures from the ALD/MLD grown hybrids by removing the organic part by simple annealing or wet-etching procedures [15

Growth and characterization of CNT–TiO₂ heterostructures

• Yucheng Zhang,
• Ivo Utke,
• Johann Michler,
• Gabriele Ilari,
• Marta D. Rossell and
• Rolf Erni

Beilstein J. Nanotechnol. 2014, 5, 946–955, doi:10.3762/bjnano.5.108

• on large area polystyrene bead arrays [31]. After removing the polystyrene, a transparent, electrically conductive, hollow sphere array was obtained on top of which an urchin-inspired nanobuilding block design of a solar cell with n-type ZnO nanowires could be realized by using electrochemical

Optical modeling-assisted characterization of dye-sensitized solar cells using TiO₂ nanotube arrays as photoanodes

• Jung-Ho Yun,
• Il Ku Kim,
• Yun Hau Ng,
• Lianzhou Wang and
• Rose Amal

Beilstein J. Nanotechnol. 2014, 5, 895–902, doi:10.3762/bjnano.5.102

• . Figure 5 shows the calculated electric field intensity of the DSSCs with different TNT lengths by using GTMM. The electric field formed between active layers of solar cells triggers the charge separation of electron and hole generated in the solar cell system. The electric field intensity in Figure 5a

• modeling contributes to a deeper understanding of the improved light harvesting and charge transport properties observed in the solar cell devices using 1D-TNT photoanodes. Experimental Fabrication of TNT-based DSSCs Under the anodization conditions of 60 V with ethylene glycol containing 0.5 wt % NaF and

Optical and structural characterization of oleic acid-stabilized CdTe nanocrystals for solution thin film processing

• Claudio Davet Gutiérrez-Lazos,
• Mauricio Ortega-López,
• Manuel A. Pérez-Guzmán,
• A. Mauricio Espinoza-Rivas,
• Francisco Solís-Pomar,
• Rebeca Ortega-Amaya,
• L. Gerardo Silva-Vidaurri,
• Virginia C. Castro-Peña and
• Eduardo Pérez-Tijerina

Beilstein J. Nanotechnol. 2014, 5, 881–886, doi:10.3762/bjnano.5.100

• quantum effect based devices [11] such as light emitting diodes [12], biolabeling [13], thermoelectric generators [14] and thin film solar cells [15]. In solar cell technology, colloidal nanocrystals hold promise for producing cheap solar cells with improved conversion efficiency by using quantum effects

One-step synthesis of high quality kesterite Cu₂ZnSnS₄ nanocrystals – a hydrothermal approach

• Vincent Tiing Tiong,
• John Bell and
• Hongxia Wang

Beilstein J. Nanotechnol. 2014, 5, 438–446, doi:10.3762/bjnano.5.51

• the bright future for CZTS based PVs. The highest efficiency CZTS solar cell was made using hydrazine based sol–gel method. However, hydrazine is a highly toxic, dangerously unstable solvent and requires extra caution in handling and storage [9]. Therefore, a safer, simple yet convenient method for

Atomic layer deposition, a unique method for the preparation of energy conversion devices

• Julien Bachmann

Beilstein J. Nanotechnol. 2014, 5, 245–248, doi:10.3762/bjnano.5.26

• semiconductors, molecules and ions in electrolytes. Figure 1 summarizes the particular types of charge and energy carriers in a solar cell (left), an electrode of a lithium ion battery (center), and the water oxidation electrode of an electrolyzer (right). Despite the variety of physical states and chemical

• logics (MOSFET), magnetic memory (TMR sensors) and semiconductor memory (DRAM), ALD has the potential to also become a critical tool in the area of energy conversion. Julien Bachmann Erlangen, November 2013 Nature of the charge carriers combining or separating at an interface in a solar cell (left), a

Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures

• Rafal Pietruszka,
• Bartlomiej S. Witkowski,
• Grzegorz Luka,
• Lukasz Wachnicki,
• Sylwia Gieraltowska,
• Krzysztof Kopalko,
• Eunika Zielony,
• Piotr Bieganski,
• Ewa Placzek-Popko and
• Marek Godlewski

Beilstein J. Nanotechnol. 2014, 5, 173–179, doi:10.3762/bjnano.5.17

• solar cell structures were characterized by a Scanning Electron Microscope Hitachi SU-70 with an accelerating voltage of 15 kV. PV response was measured by using current–voltage (I–V) curve tracer for fast I–V measurements with a sun simulator cl. AAA, at an illumination irradiance of 100 mW/cm2

• calculated by using the equation: where Voc is the open-circuit voltage, Jsc is the short-circuit current, and FF is the fill factor. The fill factor (FF) determines the maximum power from the PV cells. The fill factor is the ratio of the real output from the solar cell (Vm × Jm) to the product of Voc × Jsc

• . The fill factor can be expressed by the following equation: where Vm is the value of the voltage for the maximum power from a solar cell, and Jm is the value of the current for the maximum power from a solar cell. Figure 3b shows I–V characteristics for the samples A, B and C measured under an

Template based precursor route for the synthesis of CuInSe₂ nanorod arrays for potential solar cell applications

• Mikhail Pashchanka,
• Jonas Bang,
• Niklas S. A. Gora,
• Ildiko Balog,
• Rudolf C. Hoffmann and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2013, 4, 868–874, doi:10.3762/bjnano.4.98

• VLS synthesis of CuInSe2 nanowires (by Cu impregnation of In2Se3 nanowires) and the construction of a single-nanowire CIS/CdS core–shell device [4]. However, the authors estimated the efficiency of their solar cell to be below 1%, and the construction of a larger scale device with this approach still

• range and a part of the near infrared diapason as well (with a threshold that corresponds to a bandgap energy of 1.03 eV). A future challenge would be the incorporation of the 3D aligned CISe nanorod arrays as absorber material in a solar cell. Obviously, one of the main challenges towards this end is

Surface passivation and optical characterization of Al₂O₃/a-SiC_x stacks on c-Si substrates

• Gema López,
• Pablo R. Ortega,
• Cristóbal Voz,
• Isidro Martín,
• Mónica Colina,
• Anna B. Morales,
• Albert Orpella and
• Ramón Alcubilla

Beilstein J. Nanotechnol. 2013, 4, 726–731, doi:10.3762/bjnano.4.82

• thickness increases, the optical absorbance also increases up to a value of 21.1% at 300 nm. Thus, the SiCx capping layer is less attractive to be used as an antireflection layer on the illuminated side of the solar cell compared to a single 90 nm Al2O3 film. Reflectance measurements were also carried out

• treatment during the solar cell fabrication. Moreover, on the rear side of a c-Si solar cell, where the optical absorbance is not critical, an a-SiCx layer on top of the passivated Al2O3 film acts as a back reflector that reflects photons towards the bulk. This a-SiCx capping layer on the Al2O3 also

• on Al2O3 films on the rear side of the solar cell provides better back contacts and a better back reflector scheme. Experimental As starting material, n- and p-type (2.5 ± 0.3 Ωcm) FZ silicon(100) wafers with a thickness of approximately 290 µm were used. One p-type and one n-type wafer were textured

Optimization of solution-processed oligothiophene:fullerene based organic solar cells by using solvent additives

• Gisela L. Schulz,
• Marta Urdanpilleta,
• Roland Fitzner,
• Eduard Brier,
• Elena Mena-Osteritz,
• Egon Reinold and
• Peter Bäuerle

Beilstein J. Nanotechnol. 2013, 4, 680–689, doi:10.3762/bjnano.4.77

• :PC61BM solar cell with its vacuum-processed DCV5T-Bu4:C60 counterpart. Interestingly in this case, the efficiencies of the small-molecule organic solar cells prepared by using solution techniques are approaching those fabricated by using vacuum technology. This result is significant as vacuum-processed

• , “small” molecules, have the advantage of possessing a defined molecular structure that is monodisperse in nature and allows for purification and characterization, which leads to the derivation of valuable structure–property relationships. Problems with respect to reproducibility of solar cell results due

• as its solubility, this material has the unique advantage of being processable in both vacuum and solution. This allows for a direct comparison of the two deposition techniques and the resulting solar cell performances. There have been several reports describing the photovoltaic characteristics of

Kelvin probe force microscopy of nanocrystalline TiO₂ photoelectrodes

• Alex Henning,
• Gino Günzburger,
• Res Jöhr,
• Yossi Rosenwaks,
• Biljana Bozic-Weber,
• Catherine E. Housecroft,
• Edwin C. Constable,
• Ernst Meyer and
• Thilo Glatzel

Beilstein J. Nanotechnol. 2013, 4, 418–428, doi:10.3762/bjnano.4.49

• and the carrier transport. Smaller TiO2 particles lead to an increase of grain boundaries and reduce the solar cell current. Hence, we have considered it as relevant to characterize the surface potential of nanostructured TiO2 with a high-resolution method. Surface dipole changes upon dye adsorption

• variations may be due to varying material properties in general. In any case, such variations, which are clearly detectable by KPFM, may obstruct the optimal attachment of dye molecules and thus reduce the solar cell performance [25]. Microscopic surface photovoltage By combining a tunable illumination

• calculations for N719 [38] and N3 [42][63] adsorbed on anatase plane-surface. However, for a complete DSC device the surface dipole may change due to screening by the surrounding electrolyte [64]. Figure 9a depicts the I–V characteristics for three different DSCs, a bare TiO2 solar cell with electrolyte and

Low-temperature synthesis of carbon nanotubes on indium tin oxide electrodes for organic solar cells

• Andrea Capasso,
• Luigi Salamandra,
• Aldo Di Carlo,
• John M. Bell and
• Nunzio Motta

Beilstein J. Nanotechnol. 2012, 3, 524–532, doi:10.3762/bjnano.3.60

• , such as thermal [8] and solvent annealing [9], or the use of additives in the blend preparation [10]. Along with fullerenes, carbon nanotubes (CNTs) have also been suggested as promising materials to boost solar cell PCE, thanks to their excellent electrical properties and to a favorable aspect ratio

• the significant advancement of the overall PCE of the solar cell. Results and Discussion After preliminary tests in CVD, SEM and EDX analysis indicated that the range of temperature of 550–600 °C has to be avoided for the application of the ITO-substrates as electrodes, since the ITO layer undergoes

• interface. Besides, by taking into consideration an equivalent-circuit diagram for a bulk heterojunction solar cell (Figure 6), we highlight that the CNTs could be also responsible of a quenched recombination both at the dissociation sites (e.g., donor/acceptor interfaces) and near the anode (as a result of

Reduced electron recombination of dye-sensitized solar cells based on TiO₂ spheres consisting of ultrathin nanosheets with [001] facet exposed

• Hongxia Wang,
• Meinan Liu,
• Cheng Yan and
• John Bell

Beilstein J. Nanotechnol. 2012, 3, 378–387, doi:10.3762/bjnano.3.44

• °C for 15 min in an electric oven to form a thin Pt layer on the FTO substrate. A dye-sensitized solar cell was assembled by sealing the dye-coated TiO2 electrode with the platinum-coated FTO counter electrode by using a thermal plastic (Surlyn 1705) at 130 °C. The electrolyte composed of 0.6 M 1

• paste B containing 25 wt % spheres (b) with (curve B and D) and without (curve A and C) TiCl4 treatment. Equivalent circuit (a) and the Nyquist plot (b) and Bode plot (c) of the impedance spectrum of a dye-sensitized solar cell. Comparison of the effective electron lifetime, τn, (a) and effective

Structural, electronic and photovoltaic characterization of multiwalled carbon nanotubes grown directly on stainless steel

• Luca Camilli,
• Manuela Scarselli,
• Silvano Del Gobbo,
• Paola Castrucci,
• Eric Gautron and
• Maurizio De Crescenzi

Beilstein J. Nanotechnol. 2012, 3, 360–367, doi:10.3762/bjnano.3.42

• clearly resembles the behaviour of a commercial p–n silicon solar cell; in the in-plane architecture there is a further contribution at ultraviolet wavelengths, following the MWCNT optical absorbance. We can assess that in both cases the EQE spectrum is a sum of two contributions, one coming from the

• is not ohmic. Concerning the solar conversion efficiency, we obtain 0.17% in the top-down setup. This value is in accordance with recently published data obtained for a solar cell based on a MWCNT/Si heterojunction [17]. However, the nearly linear behaviour of the J–V characteristic in the fourth

• silicon solar cell, with a low absorption at ultraviolet wavelengths, whereas in the in-plane case, there is a rise that is characteristic of MWCNT absorption. J–V characteristics acquired in the dark and under illumination by white light. (a) In the in-plane geometry: Voc = 0.2 V, Jsc = 0.09 mA/cm2. In

Junction formation of Cu₃BiS₃ investigated by Kelvin probe force microscopy and surface photovoltage measurements

• Fredy Mesa,
• William Chamorro,
• William Vallejo,
• Robert Baier,
• Thomas Dittrich,
• Alexander Grimm,
• Martha C. Lux-Steiner and
• Sascha Sadewasser

Beilstein J. Nanotechnol. 2012, 3, 277–284, doi:10.3762/bjnano.3.31

• , such as chemical bath deposition, atomic layer deposition, ion layer gas reaction (ILGAR) deposition, evaporation, and spray deposition [9]. One interesting aspect of the above mentioned solar cell materials CdTe and Cu(In,Ga)Se2 is their high efficiency despite the abundance of grain boundaries (GBs

• the NH3-etched film. The change in work function amounts to 10–20 meV for the In2S3 buffer layer and to 60–150 meV for the CdS buffer layer. The size of this upward band bending is in a similar range to the band bending observed for Cu(In,Ga)Se2 solar-cell absorbers [18]. In contrast to the In2S3 and

• ), the spectral surface photovoltage revealed a passivation of defect states at the absorber/buffer interface, evidenced by a reduction of the sub-band-gap SPV. To develop the promising Cu3BiS3 semiconductor toward an efficient solar cell, future activities should include the investigation of the n-type

Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications

• Yaron Paz

Beilstein J. Nanotechnol. 2011, 2, 845–861, doi:10.3762/bjnano.2.94

Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

• Tanujjal Bora,
• Htet H. Kyaw,
• Soumik Sarkar,
• Samir K. Pal and
• Joydeep Dutta

Beilstein J. Nanotechnol. 2011, 2, 681–690, doi:10.3762/bjnano.2.73

• the ZnO/Au interface. For large area DSSC (1 cm2), ~130% enhancement in PCE (from 0.50% to 1.16%) was achieved after incorporation of the Au nanoparticles into the ZnO nanorods. Keywords: dye-sensitized solar cell; gold nanoparticle; picosecond spectroscopy; Schottky barrier; zinc oxide nanorod

• ; Introduction The dye-sensitized solar cell (DSSC), also known as the Grätzel’s cell, has been one of the most extensively studied types of solar cell in the last two decades due to its potential widespread application attributed to lower manufacturing costs [1][2][3]. Currently one of the major issues

• illumination under a light intensity of 100 mW/cm2 (1 sun, air mass (AM) 1.5 G), the bare ZnO-nanorod solar cell exhibited short-circuit current density (Jsc) of 18.80 μA/cm2 and open-circuit voltage (Voc) of 0.27 V. On the other hand, the ZnO/Au-nanocomposite solar cell, under illumination, demonstrated

Schottky junction/ohmic contact behavior of a nanoporous TiO₂ thin film photoanode in contact with redox electrolyte solutions

• Masao Kaneko,
• Hirohito Ueno and
• Junichi Nemoto

Beilstein J. Nanotechnol. 2011, 2, 127–134, doi:10.3762/bjnano.2.15

• junction, which generates a photocurrent. A crystalline n-TiO2 photoanode to decompose water by UV light attracted a great attention [3]; organic compounds have also been similarly decomposed [4][5]. Later, a nanoporous TiO2 thin film was applied to a dye-sensitized solar cell (DSSC) [6] in which the

• mesoporous TiO2 thin film can function as a good electron-conductive material under irradiation conditions when a strong electron donor is present in the liquid. It should be noted that in a dye-sensitized solar cell (DSSC) [6], a mesoporous TiO2 thin film also functions as an electron conductor under