The Intermediate Band Solar Cell: Progress Toward the Realization of an Attractive Concept

The intermediate band (IB) solar cell has been proposed to increase the current of solar cells while at the same time preserving the output voltage in order to produce an efficiency that ideally is above the limit established by Shockley and Queisser in 1961. The concept is described and the present realizations and acquired understanding are explained. Quantum dots are used to make the cells but the efficiencies that have been achieved so far are not yet satisfactory. Possible ways to overcome the issues involved are depicted. Alternatively, and against early predictions, IB alloys have been prepared and cells that undoubtedly display the IB behavior have been fabricated, although their efficiency is still low. Full development of this concept is not trivial but it is expected that once the development of IB solar cells is fully mastered, IB solar cells should be able to operate in tandem in concentrators with very high efficiencies or as thin cells at low cost with efficiencies above the present ones

"Comment on "Thermodynamics limits of quantum photovoltaic cell efficiency" [Appl. Phys. Lett. 91, 223507 (2007)]"

This article claims the photovoltaic cell efficiency calculated using the Luque and Marti model

Can Impurities be Beneficial to Photovoltaics?

The state of the art of the intermediate band solar cells is presented with emphasis on the use of impurities or alloys to form bulk intermediate band materials. Quantum dot intermediate band solar cells start to present already attractive efficiencies but many difficulties jeopardize the immediate achievement of record efficiency cells. To complement this research it is worthwhile examining bulk materials presenting an IB. Four or perhaps more materials have already proven to have it and several paths for the research of more are today open but no solar cell has yet been published based on them. This topic has already attracted many researches and abundant funds for their development worldwide

Experimental advances in the next generation of solar cells

We consider next generation solar cells concepts those that have the potential to exceed the limiting efficiency calculated by Shockley and Queisser for single gap solar cells (40.7 %) and still have not been commercialized. Among these concepts, this paper deals with the multiple exciton generation (or impact ionization or multiple carrier generation) solar cell, the intermediate band solar cell and the hot carrier solar cell. These concepts were proposed theoretically more than ten years ago. In the last years, the number of experiments supporting the theories behind and paving the way towards their practical implementation has leaped forward. This work reviews these experimental advance

Key issues on partial least squares (PLS) in operations management research: A guide to submissions

Purpose: This work aims to systematise the use of PLS as an analysis tool via a usage guide or recommendation for researchers to help them eliminate errors when using this tool. Design/methodology/approach: A recent literature review about PLS and discussion with experts in the methodology. Findings: This article considers the current situation of PLS after intense academic debate in recent years, and summarises recommendations to properly conduct and report a research work that uses this methodology in its analyses. We particularly focus on how to: choose the construct type; choose the estimation technique (PLS or CB-SEM); evaluate and report the measurement model; evaluate and report the structural model; analyse statistical power. Research limitations: It was impossible to cover some relevant aspects in considerable detail herein: presenting a guided example that respects all the report recommendations presented herein to act as a practical guide for authors; does the specification or evaluation of the measurement model differ when it deals with first-order or second-order constructs?; how are the outcomes of the constructs interpreted with the indicators being measured with nominal measurement levels?; is the Confirmatory Composite Analysis approach compatible with recent proposals about the Confirmatory Tetrad Analysis (CTA)? These themes will the object of later publications. Originality/value: We provide a check list of the information elements that must contain any article using PLS. Our intention is for the article to act as a guide for the researchers and possible authors who send works to the JIEM (Journal of Industrial and Engineering Management). This guide could be used by both editors and reviewers of JIEM, or other journals in this area, to evaluate and reduce the risk of bias (Losilla, Oliveras, Marin-Garcia & Vives, 2018) in works using PLS as an analysis procedure

A vueltas con las SICAV. Reflexiones críticas desde el punto de vista económico-tributario

SICAVs are a type of investment society which are receiving "specific media attention" because, at least in appearance, they are an instrument which enables the channelling of investment by the large equities/net worths benefiting from a nominal type in corporate tax of only 1%. This paper analyses the patrimonial evolution and its distribution between the different components from 2001 to 2014. The possible existence of law fraud in the use of this figure is discussed, when instrumented by one or more people associated for the purpose of obtaining a tributary saving outside the object (collective investment) of society. The repercussions of the fact that competition for tributary control of the SICAV resides in the CNMV instead of the State Tributary Administration Agency is analysed. Finally, some observations regarding the potential risk of capital flight that has sometimes served as justification for the establishment of a privileged legal regime are presented.Las Sociedades de Inversión de Capital Variable (SICAV) son un tipo de sociedad de inversión colectiva que viene recibiendo una "singular atención mediática” debido a que, al menos en apariencia, constituyen un instrumento para canalizar la inversión de los grandes patrimonios beneficiándose de un tipo nominal en el impuesto de sociedades de tan solo el 1 %. En el trabajo se analiza la evolución patrimonial y su distribución entre los diferentes componentes desde 2001 hasta 2014. Se aborda la posible existencia de fraude de ley en la utilización de esta figura, cuando se instrumentaliza por una o varias personas vinculadas, con la finalidad de obtener un ahorro tributario al margen del objeto (inversión colectiva) de la sociedad. Se analiza las repercusiones que tiene el hecho de que la competencia sobre el control tributario de las SICAV resida en la CNMV en lugar de la Agencia Estatal de Administración Tributaria. Por último, se presentan una serie de reflexiones, en relación con el posible riesgo de fuga de capitales que en ocasiones ha servido de justificación para el establecimiento de un régimen jurídico privilegiado

A vueltas con la SICAV. Reflexiones críticas desde el punto de vista económico-tributario

Las Sociedades de Inversión de Capital Variable (SICAV) son un tipo de sociedad de inversión colectiva que viene recibiendo una "singular atención mediática” debido a que, al menos en apariencia, constituyen un instrumento para canalizar la inversión de los grandes patrimonios beneficiándose de un tipo nominal en el impuesto de sociedades de tan solo el 1 %. En el trabajo se analiza la evolución patrimonial y su distribución entre los diferentes componentes desde 2001 hasta 2014. Se aborda la posible existencia de fraude de ley en la utilización de esta figura, cuando se instrumentaliza por una o varias personas vinculadas, con la finalidad de obtener un ahorro tributario al margen del objeto (inversión colectiva) de la sociedad. Se analiza las repercusiones que tiene el hecho de que la competencia sobre el control tributario de las SICAV resida en la CNMV en lugar de la Agencia Estatal de Administración Tributaria. Por último, se presentan una serie de reflexiones, en relación con el posible riesgo de fuga de capitales que en ocasiones ha servido de justificación para el establecimiento de un régimen jurídico privilegiado

La metodologia en Reforma. Aproximació actual

Amb el present article, el que s'intenta expressar és la dificultat que està trobant el professorat d'ensenyament secundari, en el moment actual (últims anys d'implantació de la Reforma), per tal d'imposar entre l'alumnat una metodologia emancipatòria, d'acord amb la normativa dels Dissenys Curriculars Base (DCB) de les diferents comunitats autònomes. Al llarg del mateix, s'intentarà donar orientacions per tal d'aconseguir implantar aquestes metodologies, malgrat que ens arribi un alumnat completament passiu i sense iniciativa (cosa prou comú en els darrers temps, tant en l'educació com en altres camps). Així, per exemple, s'intentarà que, partint d'una metodologia d'instrucció directa (a la qual n'estan ben acostumats), n'arribin a una de resolució de plantejaments, a poc a poc, utilitzant metodologies intermèdies

Nanotechnology for more efficient photovoltaics: the quantum dot intermediate band solar cell

The intermediate band solar cell [1] has been proposed as a concept able to substantially enhance the efficiency limit of an ordinary single junction solar cell. If a band permitted for electrons is inserted within the forbidden band of a semiconductor then a novel path for photo generation is open: electron hole pairs may be formed by the successive absorption of two sub band gap photons using the intermediate band (IB) as a stepping stone. While the increase of the photovoltaic (PV) current is not a big achievement —it suffices to reduce the band gap— the achievement of this extra current at high voltage is the key of the IB concept. In ordinary cells the voltage is limited by the band gap so that reducing it would also reduce the band gap. In the intermediate band solar cell the high voltage is produced when the IB is permitted to have a Quasi Fermi Level (QFL) different from those of the Conduction Band (CB) and the Valence Band (VB). For it the cell must be properly isolated from the external contacts, which is achieved by putting the IB material between two n- and p-type ordinary semiconductors [2]. Efficiency thermodynamic limit of 63% is obtained for the IB solar cell1 vs. the 40% obtained [3] for ordinary single junction solar cells. Detailed information about the IB solar cells can be found elsewhere [4]