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Methylammonium lead iodide (CH3NH3PbI3; MAPbI3) films were fabricated from sputtered lead sulfide (PbS) films prepared at various substrate temperatures according to the Thornton structural zone model. PbS films were converted to lead iodide (PbI2) and finally to MAPbI3in a two-step gas-phase reaction. The increase in substrate temperature caused the morphology to change to fibrous interconnected grains, which played an important role in improving the optoelectrical properties of perovskite films. Moreover, enhanced charge transport of MAPbI3films was observed owing to the fibrous interconnected PbI2precursor, which was confirmed by a higher absorption coefficient and longer carrier lifetime.

We evaluate the use of p‐type silicon oxide (p‐SiOx) dielectric layers as a boron diffusion source for n‐type crystalline silicon (c‐Si) substrates. The p‐SiOxlayers grown on n‐type c‐Si substrates by plasma enhanced chemical vapor deposition using a gas mixture of He/hexamethyldisiloxane/CO2/B2H6are thermally stable and do not peel off during annealing up to 1050 °C, making them effective diffusion sources. The layers were examined before and after annealing with characterization techniques including spectroscopic ellipsometry and secondary ion mass spectrometry. We observe that there is a reduction in the thickness of the p‐SiOxlayer after annealing by about 50%, and that boron diffuses into the n‐type c‐Si substrate, forming a p+layer, limited by the formation of a carbon‐rich layer above the c‐Si surface. The concentration of holes in the diffused region was measured by the electrochemical capacitance–voltage technique, and it was found that essentially all the boron that diffused into the n‐type c‐Si was active, unaffected by the presence of carbon and oxygen atoms. The concentration of carriers can be controlled by the initial thickness of the p‐SiOxlayers and the depth of the p+/n junction can be controlled by the time of annealing. A surface carrier concentration of 3 × 1019at cm−3and a sheet resistance of the order of 120 Ω sq−1was obtained upon annealing at 1050 °C for 30 min.

Developing structures that provide excellent light absorption while keeping a high surface passivation quality is a mandatory issue for crystalline Si solar cells. In this study, Si nanowires grown on crystalline Si wafers using plasma-enhanced chemical vapor deposition (PECVD) are used as nanostructures for an efficient light absorption. Two types of stacks with direct or decoupled growth of nanowires on crystalline Si have been studied in order to identify their influence on the light absorption, as well as on the passivation quality. By choosing appropriately the stack configuration and carefully adjusting parameters such as silicon nitride thickness, Si nanowire diameters, and lengths, we have obtained an effective carrier lifetime up to 1.7 ms. Moreover, modeling has shown that a photogeneration density above 41 mA/cm2 can be expected in the c-Si wafer.

In recent years, there has been an increasing interest on the study of the complex interplay between the nanostructure and phototransport mechanism in many emerging photovoltaic technologies. Recently, Kelvin probe force microscopy has emerged as a powerful technique for probing photocarrier dynamics and gaining access to carrier lifetime at the nanoscale in a wide range of photovoltaic materials. In the paper entitled “Nanoscale investigation of carrier lifetime on the cross section of epitaxial silicon solar cells using Kelvin Probe Force Microscopy” by Narchi et al. (IEEE J. Photovolt., vol. 6, no. 6, pp. 1576-1580, Nov. 2016), an innovative method to asses minority carrier lifetime at the nanoscale using Kelvin probe force microscopy under frequency modulated electrical bias on the cross section of an epitaxial silicon solar cell was demonstrated. The purpose of this note is to complement the results obtained by Narchi et al ., by showing that two-dimensional images of the photocarrier dynamics of different photophysical processes can be obtained upon the implementation of a postacquisition data processing. In this note, we also discuss how this photocarrier dynamical images can be linked with the underlying physical processes that take place in the sample upon carrier injection.

Two‐dimensional photonic nanostructures are fabricated by combining various lithography and etching techniques. The resulting nanopatterning possibilities range from periodic to random corrugations and from inverted nanopyramids to high aspect ratio parabolic profiles. Their experimental integration into a micron‐thin monocrystalline silicon solar cell highlights the factors to be tackled, while optical and optoelectrical simulations suggest the optimal parameters for achieving advanced light trapping and therefore, a competing thin‐film c‐Si cell technology.

The crucial influence of the interface between the gate dielectric and intrinsic layer has been studied in detail for amorphous silicon, polymorphous silicon and microcrystalline silicon bottom gate thinfilm transistors. We show that the electrical parameters of the TFTs depend directly on the quality of this interface, which can be strongly degraded by a vacuum break. A hydrogen plasma pretreatment of this interface greatly improves the electrical characterstics of polymorphous silicon TFTs, the mobility increases from 0.4 to 0.75 cm2V s while their subthreshold slope decreases from 1 to 0.7 Vdec. Moreover, we show that these improvements also translate into more stable TFT characteristics. Finally, microcrystalline silicon TFTs show the best stability and a nitrogenplasma treatment of the dielectric improves their stability.

Microcrystalline silicon films were deposited in a matrix distributed electron cyclotron resonance MDECR plasma enhanced chemical vapor deposition PECVD system using pure silane, under varying substrate bias conditions. Microstructural characterization of the films shows a lower void fraction and a preponderance of nanograins in films deposited at negative bias, while in positive bias a thin incubation layer is seen with a higher void fraction. Plasma emission studies reveal higher electron temperature and more atomic H at positive bias, which lead to early onset of crystallization. The microstructural properties of the films are correlated with the dark and phototransport properties. Our study demonstrates the importance of substrate bias in controlling the ion energy and properties of films deposited in the MDECR reactor.

Dry plasma etching is a promising technique for crystalline silicon surface texturing aimed at improving solar cell efficiencies by reducing incident light reflection and backscattering at the cell front surface. In this work we present a new optical characterization technique for textured surfaces based on a Mueller polarimeter coupled with a high numerical aperture microscope operated either in real or in angular spaces. This tool provides both the specularly reflected and the angle-resolved backscattered intensities in a very efficient manner, due to the absence of moving parts. Three different silicon samples were etched in a standard reactor with SF_6/O_2 plasmas at various RF powers, resulting in different textures that were characterized by scanning electron microscopy, standard reflectometry, and by our tool. The three techniques yielded consistent results. However, reflectometry could not take into account the backscattered light from highly textured surfaces, leading to significant underestimation of the overall amount of the reflected light. In contrast, our tool has demonstrated the potential to measure both reflected and backscattered light quickly and efficiently for all samples, paving the way for a new characterization technique for textured solar cells both at the development and at the production stage.

The formation of gold islands on a transparent conductive oxide by annealing a thin evaporated layer is studied by SEM. The droplets of metal formed this way may catalyze the growth of nanowires or nanotubes to be used in opto-electronic devices. The effect of the initial thickness (between 1 nm and 4 nm) and the annealing temperature (between 70 °C and 650 °C) is investigated. A qualitative description of the evolution is given and quantitative data are obtained by automated image analysis. Number density, area and effective diameter of the aggregates depend heavily on the initial thickness but very slightly on the annealing temperature. Three phenomena are considered to explain the evolution: interfacial stress due to mismatch in the linear expansion coefficient, Ostwald ripening and kinetic aggregation. By comparing the experimental size distributions to the theoretical ones, the relevance of the last two is discussed. As an application, the gold catalyzed CVD growth of silicon nanowires on zinc oxide is demonstrated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Powder formation in silane plasmas has been considered as a technology drawback because it might lead to the formation of macroscopic defects in the deposited layers. Here we summarize our recent efforts in controlling the formation of powder precursors, in particular, nanocrystalline silicon particles, aiming at their incorporation in the films. Indeed, the incorporation of clusters and crystallites along with SiHx radicals allows production of polymorphous silicon films with improved structure and transport properties with respect to standard amorphous silicon films.

L’électricité d’origine solaire photovoltaïque (PV) a connu des progrès spectaculaires, au point qu’elle est en train de devenir compétitive par rapport aux sources conventionnelles. Cette réussite est le résultat de la convergence de plusieurs domaines (matériaux, physique, chimie, optique et électronique) sur un objectif commun : l’augmentation du rendement de conversion et la réduction des coûts de production. Nous présentons ici l’état de l’art au niveau de la recherche et de la production industrielle, ainsi que les défis à résoudre, pour lesquels beaucoup d’attentes reposent sur l’optique.