75 research outputs found
Mixed AgBiS2 nanocrystals for photovoltaics and photodetectors
Heavy-metal-free colloidal nanocrystals are gaining due attention as low-cost, semiconducting materials for solution-processed optoelectronic applications. One common limitation of such materials is their limited carrier transport and trap-assisted recombination, which impede the performance of thick photoactive layers. Here we mix small-size and large-size AgBiS2 nanocrystals to judiciously favour the band alignment in photovoltaic and photodetector devices. The absorbing layer of these devices is fabricated in a gradient fashion in order to maximise charge transfer and transport. We implement this strategy to fabricate mixed AgBiS2 thin film solar cells with a power conversion of 7.3%, which significantly surpasses the performance of previously reported devices based on single-batch AgBiS2 nanocrystals. Additionally, this approach allows us to fabricate devices using thicker photoactive layers that show lower dark currents and external quantum efficiencies exceeding 40% over a broad bandwidth â covering the visible and near infrared range beyond 1 ÎŒm, thus unleashing the potential of colloidal AgBiS2 nanocrystals in photodetector applications.Peer ReviewedPostprint (published version
High Performance Inverted Organic Photovoltaics Without Hole Selective Contact
A detailed investigation of the functionality of inverted organic
photovoltaics (OPVs) using bare Ag contacts as top electrode is presented. The
inverted OPVs without hole transporting layer (HTL) exhibit a significant gain
in hole carrier selectivity and power conversion efficiency (PCE) after
exposure in ambient conditions. Inverted OPVs comprised of
ITO/ZnO/poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester
(P3HT:PCBM)/Ag demonstrate over 3.5% power conversion efficiency only if the
devices are exposed in air for over 4 days. As concluded through a series of
measurements, the oxygen presence is essential to obtain fully operational
solar cell devices without HTL. Moreover, accelerated stability tests under
damp heat conditions (RH=85% and T=65oC) performed to non-encapsulated OPVs
demonstrate that HTL-free inverted OPVs exhibit comparable stability to the
reference inverted OPVs. Importantly, it is shown that bare Ag top electrodes
can be efficiently used in inverted OPVs using various high performance
polymer:fullerene bulk heterojunction material systems demonstrating 6.5% power
conversion efficiencies
HighâVolume Processed, ITOâFree Superstrates and Substrates for RollâtoâRoll Development of Organic Electronics
The fabrication of substrates and superstrates prepared by scalable rollâtoâroll methods is reviewed. The substrates and superstrates that act as the flexible carrier for the processing of functional organic electronic devices are an essential component, and proposals are made about how the general availability of various forms of these materials is needed to accelerate the development of the field of organic electronics. The initial development of the replacement of indiumâtinâoxide (ITO) for the flexible carrier materials is described and a description of how rollâtoâroll processing development led to simplification from an initially complex makeâup to higher performing materials through a more simple process is also presented. This process intensification through process simplification is viewed as a central strategy for upscaling, increasing throughput, performance, and cost reduction
Organic photovoltaic cells â promising indoor light harvesters for self-sustainable electronics
Photovoltaic cells are attracting significant interest for harvesting indoor light for low power consumption wireless electronics such as those required for smart homes and offices, and the rapidly-growing Internet of Things. Here, we explore the potential of solution processable, small molecule photovoltaic cells as indoor power sources. By optimizing solvent vapour annealing (SVA) time to the photovoltaic layer, a balance between its crystallization and phase separation is obtained, resulting in a record power conversion efficiency of over 28 % under fluorescent lamps of 1000 lux, generating a maximum power density of 78.2 ”W/cm2 (>10 % efficiency under AM1.5G). This high indoor performance surpasses silicon based photovoltaic cells, and is similar to gallium arsenide photovoltaic cells. Besides, the ratios of the voltage at maximum power point to the open circuit voltage are similar from indoor lighting to one sun condition, which is unique and allows a less power consuming method to track the maximum power point for a broad range of light intensities (potentially attractive for wearable PV). New insight on the effect of SVA to the indoor and one sun performance is provided by advanced optoelectronic characterization techniques, which shows that the mobility-lifetime products as a function of charge carrier density can be correlated well to the performance at different light levels. Our results suggest that organic photovoltaic cell could be promising as indoor power source for self-sustainable electronics
Development of Lab-to-Fab Production Equipment Across Several Length Scales for Printed Energy Technologies, Including Solar Cells
Prospective evaluation of the conversion rate in the receptor status between primary breast cancer and metastasis: results from the GEICAM 2009-03 ConvertHER study
Development of Lab-to-Fab Production Equipment Across Several Length Scales for Printed Energy Technologies, Including Solar Cells
Seguimiento de las guĂas españolas para el manejo del asma por el mĂ©dico de atenciĂłn primaria: un estudio observacional ambispectivo
Objetivo
Evaluar el grado de seguimiento de las recomendaciones de las versiones de la GuĂa española para el manejo del asma (GEMA 2009 y 2015) y su repercusiĂłn en el control de la enfermedad.
Material y métodos
Estudio observacional y ambispectivo realizado entre septiembre del 2015 y abril del 2016, en el que participaron 314 médicos de atención primaria y 2.864 pacientes.
Resultados
Utilizando datos retrospectivos, 81 de los 314 mĂ©dicos (25, 8% [IC del 95%, 21, 3 a 30, 9]) comunicaron seguir las recomendaciones de la GEMA 2009. Al inicio del estudio, 88 de los 314 mĂ©dicos (28, 0% [IC del 95%, 23, 4 a 33, 2]) seguĂan las recomendaciones de la GEMA 2015. El tener un asma mal controlada (OR 0, 19, IC del 95%, 0, 13 a 0, 28) y presentar un asma persistente grave al inicio del estudio (OR 0, 20, IC del 95%, 0, 12 a 0, 34) se asociaron negativamente con tener un asma bien controlada al final del seguimiento. Por el contrario, el seguimiento de las recomendaciones de la GEMA 2015 se asociĂł de manera positiva con una mayor posibilidad de que el paciente tuviera un asma bien controlada al final del periodo de seguimiento (OR 1, 70, IC del 95%, 1, 40 a 2, 06).
Conclusiones
El escaso seguimiento de las guĂas clĂnicas para el manejo del asma constituye un problema comĂșn entre los mĂ©dicos de atenciĂłn primaria. Un seguimiento de estas guĂas se asocia con un control mejor del asma. Existe la necesidad de actuaciones que puedan mejorar el seguimiento por parte de los mĂ©dicos de atenciĂłn primaria de las guĂas para el manejo del asma.
Objective: To assess the degree of compliance with the recommendations of the 2009 and 2015 versions of the Spanish guidelines for managing asthma (GuĂa Española para el Manejo del Asma [GEMA]) and the effect of this compliance on controlling the disease.
Material and methods: We conducted an observational ambispective study between September 2015 and April 2016 in which 314 primary care physicians and 2864 patients participated.
Results: Using retrospective data, we found that 81 of the 314 physicians (25.8%; 95% CI 21.3â30.9) stated that they complied with the GEMA2009 recommendations. At the start of the study, 88 of the 314 physicians (28.0%; 95% CI 23.4â33.2) complied with the GEMA2015 recommendations. Poorly controlled asthma (OR, 0.19; 95% CI 0.13â0.28) and persistent severe asthma at the start of the study (OR, 0.20; 95% CI 0.12â0.34) were negatively associated with having well-controlled asthma by the end of the follow-up. In contrast, compliance with the GEMA2015 recommendations was positively associated with a greater likelihood that the patient would have well-controlled asthma by the end of the follow-up (OR, 1.70; 95% CI 1.40â2.06).
Conclusions: Low compliance with the clinical guidelines for managing asthma is a common problem among primary care physicians. Compliance with these guidelines is associated with better asthma control. Actions need to be taken to improve primary care physician compliance with the asthma management guidelines
Towards industrial viability of organic solar cells: ITO-free, green solvents and technological aspects for upscalability
Des de la seva apariciĂł com a alternativa per la conversiĂł dâenergia fotovoltaica, el camp
de les cel·les solars orgà niques ha experimentat un progrés significatiu, especialment en
els darrers 15 anys. El gran interĂšs en la tecnologia fotovoltaica orgĂ nica (OPV, per les
sigles en anglÚs) es deu principalment al seu potencial baix cost. Rellevants avenços
cientĂfics han empĂšs les eficiĂšncies de conversiĂł energĂštica fins al 12%, fet que
encoratja a acostar les OPV al mercat. Tanmateix, altres aspectes decisius per la seva
industrialitzaciĂł han estat menys atesos.
Aquesta tesi tracta tres quÌestions clau que la tecnologia OPV ha dâafrontar per tal
dâassolir una transferĂšncia fiable del laboratori a la industria. En primer lloc, es
necessiten estratĂšgies pel processat i post-processat a gran escala, idealment amb un
cost reduĂŻt. En aquest treball es presenta una amplia investigaciĂł en inkjet printing. Ăs
necessari tenir un profund coneixement dâaquesta tĂšcnica compatible amb roll-to-roll
per tal dâassolir morfologies de capa adequades. Sâha trobat que la cinĂštica dâassecat de
les capes Ă©s especialment crĂtica. En relaciĂł a aixĂČ, sâha desenvolupat un nou mĂštode
per determinar patrons dâimpressiĂł apropiats per la deposiciĂł de la capa activa. A mĂ©s,
sâha demostrat lâĂșs dâun tractament alternatiu anomenat vapour printing en dispositius
OPV. Utilitzant aquest mĂštode amb vapor de dissolvent adequat, el tractament de la
capa activa es pot assolir en temps molt més curts en comparació a altres tÚcniques.
Un altre aspecte que ha estat poc atĂšs estĂ relacionat amb els dissolvents utilitzats pel
processat dels OPV, especialment per la deposiciĂł de la capa activa. TĂpicament
sâutilitzen dissolvents halogenats, com el clorbenzĂš o el diclorbenzĂš, essent alguns dâells
prohibits per aplicacions industrials. Substituir-los per formulacions verdes Ă©s, per tant,
una necessitat primordial. Per tal de trobar sistemes aptes de dissolvents verds, sâha
utilitzat un mĂštode basat en la solubilitat. Aquest mĂštode, prĂšviament demostrat per
cel·les solars polimĂšriques, sâestĂ©n de manera satisfactĂČria en aquesta tesi en dispositius
basats en petita molĂšcula. TambĂ© sâaporten nous coneixements sobre la precisiĂł del
mĂštode.
Lâoxid dâindi i estany (ITO, per les seves sigles en anglĂšs), frequÌentment utilitzat com a
elĂšctrode conductor transparent, contribueix de manera important en el cost dâun mĂČdul OPV. Altres raons per reemplaçar aquest component inclouen la seva modesta
flexibilitat i conductivitat, el que pot limitar lâextracciĂł de corrent elĂšctric en dispositius
de gran à rea. Una possible alternativa són les xarxes metà l·liques combinades amb una
capa transparent semiconductora. Tot i resoldre lâaspecte de la conductivitat, altres
factors limiten encara lâextracciĂł de corrent. El nou mĂštode utilitzat en aquest treball
per preparar aquestes estructures venç aquests factors. Es demostren dispositius
eficients lliures de ITO.Desde su apariciĂłn como alternativa para la conversiĂłn de energĂa fotovoltaica, el
campo de las células solares orgånicas ha experimentado un progreso significativo,
especialmente en los Ășltimos 15 años. El gran interĂ©s en la tecnologĂa fotovoltaica
orgånica (OPV, por sus siglas en inglés) se debe principalmente a su potencial bajo
coste. Relevantes avances cientĂficos han empujado las eficiencias de conversiĂłn
energética hasta el 12%, lo que alienta el acercamiento de las OPV al mercado. Sin
embargo, otros aspectos decisivos para su industrializaciĂłn han sido menos atendidos.
Esta tesis trata tres cuestiones clave que la tecnologĂa OPV tiene que afrontar para
alcanzar una transferencia fiable del laboratorio a la industria. En primer lugar, se
necesitan estrategias para el procesado y post-procesado a gran escala, idealmente con
un coste reducido. En este trabajo se presenta una amplia investigaciĂłn en inkjet
printing. Es necesario tener un profundo conocimiento sobre esta técnica compatible
con roll-to-roll para obtener morfologĂas de capa adecuadas. Se ha encontrado que la
cinĂ©tica de secado de la capa es especialmente crĂtica. En relaciĂłn a esto, se ha
desarrollado un nuevo método para determinar patrones de impresión adecuados para
la deposiciĂłn de la capa activa. AdemĂĄs, se ha demostrado el uso de un tratamiento
alternativo llamado vapour printing en dispositivos OPV. Utilizando este método con
vapores de disolvente aptos, el tratamiento de la capa activa se puede alcanzar en
tiempos mucho mås cortos en comparación con otras técnicas.
Otro aspecto que ha sido poco atendido estĂĄ relacionado con los disolventes utilizados
en el procesado de las OPV, especialmente en la deposiciĂłn de la capa activa.
TĂpicamente se emplean disolventes halogenados, como el clorobenceno o
diclorobenzeno, estando alguno de ellos prohibidos en aplicaciones industriales. Su
substituciĂłn por formulaciones verdes es, por tanto, una necesidad primordial. Para
encontrar sistemas aptos de disolventes verdes, se ha utilizado un método basado en la solubilidad. Este método, previamente demostrado para células solares poliméricas, se
extiende de manera exitosa en esta tesis para dispositivos basados en pequeña molécula.
También se aportan nuevos conocimientos sobre la precisión del método.
El óxido de indio y estaño (ITO, por sus siglas en inglés), frecuentemente utilizado
como electrodo conductor transparente, contribuye de manera importante en el coste
de un mĂłdulo OPV. Otros motivos para substituir este componente incluyen su
modesta flexibilidad y conductividad, lo que puede limitar la extracciĂłn de corriente
eléctrica en dispositivos de gran årea. Una posible alternativa son las redes metålicas
combinadas con una capa transparente semiconductora. A pesar de que el aspecto de la
conductividad queda solucionado, otros factores limitan aĂșn la extracciĂłn de corriente.
El nuevo método utilizado en este trabajo para preparar estas estructuras vence estos
aspectos. Se demuestran dispositivos eficientes libres de ITO.Since its emergence as an alternative for photovoltaic energy conversion, the field of
organic solar cells has experienced significant progress, especially in the last 15 years.
The high interest in organic photovoltaics (OPV) technology is mostly due to its lowcost
potential. Relevant scientific advances have pushed power conversion efficiencies
up to 12%, which is encouraging for bringing OPV to market. However, other decisive
aspects for their industrialisation have been less attended.
This thesis deals with three key issues that OPV technology has to face in order to
achieve a reliable lab-to-fab transfer. First, approaches for large-scale processing and
post-processing are needed, ideally with reduced cost. In this work a broad
investigation in inkjet printing is presented. A deep understanding on this roll-to-roll
compatible technique is necessary to achieve suitable layer morphology. The drying
kinetics of the wet film has been found to be especially critical. In relation to this, a
new method to determine appropriate printing patterns for active layer deposition has
been developed. Moreover, an alternative post-processing treatment called vapour
printing is demonstrated for OPV devices. Using this method with suitable solvent
vapour, the annealing of the active layer can be achieved in much shorter times as
compared to other treatments.
Another aspect that has been poorly attended is related to the solvents used for OPV
processing, specifically for active layer deposition. Typically halogenated solvents such
as chlorobenzene or o-dichlorobenzene are employed, being some of them banned for
industrial applications. Their replacement by green formulations is therefore a major
need. In order to find suitable green solvent systems, a method based on solubility has
been used. This method, previously demonstrated for polymeric solar cells, is
successfully extended in this thesis for small molecule based devices. New insights into
the accuracy of the method are also provided.
A major contributor to the cost of an OPV module is the indium-tin-oxide (ITO),
commonly used as a transparent conductive electrode. Further reasons to replace this
component include its modest flexibility and conductivity, which may limit current
extraction in large area devices. One possible alternative are metallic grids combined
with a transparent semiconductor layer. Although the conductivity issue is solved,
other factors still limit current extraction. The new method used in this work to prepare such structures overcomes these features. Efficient, ITO-free devices are
demonstrated
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