Push-pull photochromic dyes for semi-transparent solar cells with light-adjustable optical properties and high color-rendering index.

We report the design, synthesis and characterization of push-pull photochromic naphthopyran dyes, incorporating different carbazole moieties as the electron-donor group for use in dye-sensitized solar cells. Compared to a reference dye incorporating a diphenylamine-type donor moiety, the introduction of functionalized carbazoles allows for a hypsochromic shift of the absorption of the coloured isomers of the dyes in the visible region and a better tuning of their spectra to the photopic response of the human eye. Under illumination, the molecules exhibit a broad absorption with a maximum comprised between 546 nm and 571 nm in solution and they reveal relatively fast discoloration kinetics. By using these dyes to fabricate photochromic solar cells whose optical and photovoltaic properties vary with the light exposure, we have achieved a PCE of up to 3% in opaque cells. Using these molecules in semi-transparent solar cells with different electrolytes, a PCE of 2.3% was achieved. We also produced a semi-transparent mini-module with an average visible transmittance varying between 66% and 50% and a colour rendering index around 95 in both the uncoloured and coloured states.

Star-shape non-fullerene acceptor featuring an aza-triangulene core for organic solar cells.

We present the simple synthesis of a star-shape non-fullerene acceptor (NFA) for application in organic solar cells. This NFA possesses a D(A)3 structure in which the electron-donating core is an aza-triangulene unit and we report the first crystal structure for a star shape NFA based on this motive. We fully characterized this molecule's optoelectronic properties in solution and thin films, investigating its photovoltaic properties when blended with PTB7-Th as the electron donor component. We demonstrate that the aza-triangulene core leads to a strong absorption in the visible range with an absorption edge going from 700 nm in solution to above 850 nm in the solid state. The transport properties of the pristine molecule were investigated in field effect transistors (OFETs) and in blends with PTB7-Th following a Space-Charge-Limited Current (SCLC) protocol. We found that the mobility of electrons measured in films deposited from o-xylene and chlorobenzene are quite similar (up to 2.70 × 10-4 cm2 V-1 s-1) and that the values are not significantly modified by thermal annealing. The new NFA combined with PTB7-Th in the active layer of inverted solar cells leads to a power conversion efficiency of around 6.3% (active area 0.16 cm2) when processed from non-chlorinated solvents without thermal annealing. Thanks to impedance spectroscopy measurements performed on the solar cells, we show that the charge collection efficiency of the devices is limited by the transport properties rather than by recombination kinetics. Finally, we investigated the stability of this new NFA in various conditions and show that the star-shape molecule is more resistant against photolysis in the presence and absence of oxygen than ITIC.

Influence of Redox Couple on the Performance of ZnO Dye Solar Cells and Minimodules with Benzothiadiazole-Based Photosensitizers.

ZnO-based dye-sensitized solar cells exhibit lower efficiencies than TiO2-based systems despite advantageous charge transport dynamics and versatility in terms of synthesis methods, which can be primarily ascribed to compatibility issues of ZnO with the dyes and the redox couples originally optimized for TiO2. We evaluate the performance of solar cells based on ZnO nanomaterial prepared by microwave-assisted solvothermal synthesis, using three fully organic benzothiadiazole-based dyes YKP-88, YKP-137, and MG-207, and alternative electrolyte solutions with the I-/I3 -, Co(bpy)3 2+/3+, and Cu(dmp)2 1+/2+ redox couples. The best cell performance is achieved for the dye-redox couple combination YKP-88 and Co(bpy)3 2+/3+, reaching an average efficiency of 4.7% and 5.0% for the best cell, compared to 3.7% and 3.9% for the I-/I3 - couple with the same dye. Electrical impedance spectroscopy highlights the influence of dye and redox couple chemistry on the balance of recombination and regeneration kinetics. Combined with the effects of the interaction of the redox couple with the ZnO surface, these aspects are shown to determine the solar cell performance. Minimodules based on the best systems in both parallel and series configurations reach 1.5% efficiency for an area of 23.8 cm2.

Photochromic spiro-indoline naphthoxazines and naphthopyrans in dye-sensitized solar cells.

Photochromic dyes possess unique properties that can be exploited in different domains, including optics, biomedicine and optoelectronics. Herein, we explore the potential of photochromic spiro-indoline naphthoxazine (SINO) and naphthopyran (NIPS) for application in photovoltaics. We designed and synthesized four new photosensitizers with a donor-pi-acceptor structure embedding SINO and NIPS units as photochromic cores. Their optical, photochromic and acidochromic properties were thoroughly studied to establish structure-properties relationships. Then, after unravelling the possible forms adopted depending on the stimuli, their photovoltaic properties were evaluated in DSSCs. Although the photochromic behavior is not always preserved, we elucidate the interplay between photochromic, acidochromic and photovoltaic properties and we demonstrate that these dyes can act as photosensitizers in DSSCs. We report a maximum power conversion efficiency of 2.7% with a NIPS-based dye, a tenfold improvement in comparison to previous works on similar class of compounds. This work opens new perspectives of developments for SINO and NIPS in optical and photovoltaic devices, and it provides novel research directions to design photochromic materials with improved characteristics.

Photochromic naphthopyran dyes incorporating a benzene, thiophene or furan spacer: effect on photochromic, optoelectronic and photovoltaic properties in dye-sensitized solar cells.

We recently demonstrated that diaryl-naphthopyran photochromic dyes are efficient for sensitization of TiO2 mesoporous electrodes, thus allowing the fabrication of photo-chromo-voltaic cells that can self-adapt their absorption of light and their generation of electricity with the light intensity. Herein we report the synthesis, the characterisation of two novel photochromic dyes based on diaryl-naphthopyran core i.e NPI-ThPh and NPI-FuPh for use in Dye Sensitized Solar Cells (DSSCs). Compared to our reference dye NPI, the molecules only vary by the nature of the spacer, a thiophene or a furan, connecting the photochromic unit and the phenyl-cyano-acrylic acid moiety used as the anchoring function. We found that swapping a phenyl for a thiophene or a furan leads to an improvement of the absorption properties of the molecules both in solution and after grafting on TiO2 electrodes, however their photochromic process becomes not fully reversible. Despite better absorption in the visible range, the new dyes show poorer photochromic and photovoltaic properties in devices compared to NPI. Thanks to UV-Vis spectroscopy, DFT calculation, electrical characterization of the cells, and impedance spectroscopy, we unravel the factors limiting their performances. Our study contributes to better understand the connection between photochromic and photovoltaic properties, which is key to develop better performing molecules of this class.

Understanding equivalent circuits in perovskite solar cells. Insights from drift-diffusion simulation.

Perovskite solar cells (PSCs) have reached impressively high efficiencies in a short period of time; however, the optoelectronic properties of halide perovskites are surprisingly complex owing to the coupled ionic-electronic charge carrier dynamics. Electrical impedance spectroscopy (EIS) is a widely used characterization tool to elucidate the mechanisms and kinetics governing the performance of PSCs, as well as of many other semiconductor devices. In general, equivalent circuits are used to evaluate EIS results. Oftentimes these are justified via empirical constructions and the real physical meaning of the elements remains disputed. In this perspective, we use drift-diffusion numerical simulations of typical thin-film, planar PSCs to generate impedance spectra avoiding intrinsic experimental difficulties such as instability and low reproducibility. The ionic and electronic properties of the device, such as ion vacancy density, diffusion coefficients, recombination mechanism, etc., can be changed individually in the simulations, so their effects can be directly observed. We evaluate the resulting EIS spectra by comparing two commonly used equivalent circuits with series and parallel connections respectively, which result in two signals with significantly different time constants. Both circuits can fit the EIS spectra and by extracting the values of the elements of one of the circuits, the values of the elements of the other circuit can be unequivocally obtained. Consequently, both can be used to analyse the EIS of a PSC. However, the physical meaning of each element in each circuit could differ. EIS can produce a broad range of physical information. We analyse the physical interpretation of the elements of each circuit and how to correlate the elements of one circuit with the elements of the other in order to have a direct picture of the physical processes occurring in the device.

Characterization of Photochromic Dye Solar Cells Using Small-Signal Perturbation Techniques.

Photochromic dye-sensitized solar cells (DSSCs) are novel semi-transparent photovoltaic devices that self-adjust their optical properties to the irradiation conditions, a feature that makes them especially suitable for building integrated photovoltaics. These novel solar cells have already achieved efficiencies above 4%, and there are multiple pathways to improve the performance. In this work, we conduct a full characterization of DSSCs with the photochromic dye NPI, combining electrical impedance spectroscopy (EIS) and intensity-modulated photocurrent spectroscopy (IMPS). We argue that the inherent properties of the photochromic dye, which result in a modification of the functioning of the solar cell by the optical excitation that also acts as a probe, pose unique challenges to the interpretation of the results using conventional models. Absorption of light in the visible range significantly increases when the NPI dye is in the activated state; however, the recombination rate also increases, thus limiting the efficiency. We identify and quantify the mechanism of enhanced recombination when the photochromic dye is activated using a combination of EIS and IMPS. From the comparison to a state-of-the-art reference dye (RK1), we were able to detect a new feature in the IMPS spectrum that is associated with the optical activation of the photochromic dye, providing a useful tool for assessing the electronic behavior of the device under different conditions of light excitation. This study provides guidelines to adequate characterization protocols of photochromic solar cells and essential insights on the interfacial electronic processes.

Illumination Intensity Dependence of the Recombination Mechanism in Mixed Perovskite Solar Cells.

Recombination mechanisms in solar cells are frequently assessed through the determination of ideality factors. In this work we report an abrupt change of the value of the "apparent" ideality factor (nAP ) in high-efficiency FA0.71 MA0.29 PbI2.9 Br0.1 based mesoscopic perovskite solar cells as a function of light intensity. This change is manifested as a transition from a regime characterized by nAP ∼1.8-2.5 at low light intensities (<10 mWcm-2 ) to one characterized by nAP ∼1. This transition is equally observed in the recombination resistance extracted from open-circuit impedance measurements. We use drift-diffusion simulations with explicit consideration of ion migration to determine the origin of this transition. We find that a change ofrecombination mechanism concurrent with a modification of the concentration of ionic vacancies is the most likely explanation of the observed behaviour. In the drift-diffusion simulations we show that the apparent ideality factor is in fact affected by the ion vacancy concentration so it is not the optimal parameter to assess the dominant recombination mechanism. We argue that a procedure based on a recently derived "electronic" ideality factor obtained from the high frequency feature of the impedance spectrum is better suited to determine the recombination route that dictates the photovoltage.

Identification of recombination losses and charge collection efficiency in a perovskite solar cell by comparing impedance response to a drift-diffusion model.

Interpreting the impedance response of perovskite solar cells (PSCs) is significantly more challenging than for most other photovoltaics. This is for a variety of reasons, of which the most significant are the mixed ionic-electronic conduction properties of metal halide perovskites and the difficulty in fabricating stable, and reproducible, devices. Experimental studies, conducted on a variety of PSCs, produce a variety of impedance spectra shapes. However, they all possess common features, the most noteworthy of which is that they have at least two features, at high and low frequency, with different characteristic responses to temperature, illumination and electrical bias. The impedance response has commonly been analyzed in terms of sophisticated equivalent circuits that can be hard to relate to the underlying physics and which complicates the extraction of efficiency-determining parameters. In this paper we show that, by a combination of experiment and drift-diffusion (DD) modelling of the ion and charge carrier transport and recombination within the cell, the main features of common impedance spectra are well reproduced by the DD simulation. Based on this comparison, we show that the high frequency response contains all the key information relating to the steady-state performance of a PSC, i.e. it is a signature of the recombination mechanisms and provides a measure of charge collection efficiency. Moreover, steady-state performance is significantly affected by the distribution of mobile ionic charge within the perovskite layer. Comparison between the electrical properties of different devices should therefore be made using high frequency impedance measurements performed in the steady-state voltage regime in which the cell is expected to operate.

Photochromic dye-sensitized solar cells with light-driven adjustable optical transmission and power conversion efficiency.

Semi-transparent photovoltaics only allows for the fabrication of solar cells with an optical transmission that is fixed during their manufacturing resulting in a trade-off between transparency and efficiency. For the integration of semi-transparent devices in building, ideally solar cells should generate electricity while offering the comfort for users to self-adjust their light transmission with the intensity of the daylight. Here we report a photochromic dye-sensitized solar cell (DSSC) based on donor-π-conjugated bridge-acceptor structures where the π-conjugated bridge is substituted for a diphenyl-naphthopyran photochromic unit. DSSCs show change in colour and self-adjustable light transmittance when irradiated with visible light and a power conversion efficiency up to 4.17%. The colouration-decolouration process is reversible and these DSSCs are stable over 50 days. We also report semi-transparent photo-chromo-voltaic mini-modules (23 cm2) exhibiting a maximum power output of 32.5 mW after colouration.

Test Anxiety in Adolescent Students: Different Responses According to the Components of Anxiety as a Function of Sociodemographic and Academic Variables.

OBJECTIVE: Test anxiety (TA) is a construct that has scarcely been studied based on Lang's three-dimensional model of anxiety. The objective of this article is to investigate the repercussion of sociodemographic and academic variables on different responses for each component of anxiety and for the type of test in adolescent students. METHOD: A total of 1181 students from 12 to 18 years old (M = 14.7 and SD = 1.8) participated, of whom 569 were boys (48.2%) and 612 girls (51.8%). A sociodemographic questionnaire and the Cuestionario de Ansiedad ante los examenes-Adaptado (CAEX-A) [Test Anxiety Questionnaire-Adapted] an adaptation for Spanish secondary school levels (ESO) and Bachillerato were administered. RESULTS: Girls scored higher on the cognitive and physiological components of TA than boys, the intensity of the physiological response increasing with age. Bachillerato level students reported more physiological anxiety than those of ESO level. Students with better marks in the previous year presented more anxiety in the cognitive component, while those who obtained the lower mark presented higher anxiety values in the behavioral component. Participants reported that the types of tests that cause them more anxiety were oral tests in front of the class, oral presentation in front of a panel, and mathematics tests. CONCLUSION: Adolescents show a differential response of TA based on the physiological, cognitive and motor components, mediated by the variables of gender, age, grade, academic performance and type of exam. These results serve to design specific intervention programs to manage anxiety in situations of academic assessment.

Implicaciones de la edad y el país de pertenencia en la relación entre apoyo emocional percibido y depresión: un estudio transcultural / Implications of age and country of membership in the relationship between perceived emotional support and depression: a cross-cultural study

En el presente trabajo nos proponemos profundizar en el estudio de las implicaciones que la edad y los factores de tipo cultural asociados a la nacionalidad, puedan presentar respecto a la relación entre apoyo social y depresión. Con este objetivo, se ha entrevistado a una muestra total de 1503 personas de edad adulta (jóvenes, adultos y personas de edad avanzada) pertenecientes a España, Cuba y México. Para la evaluación de la depresión, se ha empleado el cuestionario CES-D, mientras que para la evaluación del apoyo emocional percibido y la satisfacción con el mismo, se aplicó un modelo estructurado de autoinforme elaborado por nosotros en el que se recoge la percepción de disponibilidad de apoyo emocional en diferentes fuentes (pareja, familiares, amigos, compañeros, vecinos) y la satisfacción con el mismo. Los resultados obtenidos indican que la relación obtenida entre apoyo emocional percibido según distintas fuentes y los valores en sintomatología depresiva está sujeta a variaciones en función de las influencias culturales asociadas al país de pertenencia de los sujetos entrevistados, y a su edad, así como a la interacción entre ambas variables

The purpose of this study has been to analyze the implications that the age and the cultural factors associated with the nationality, to submit to the relationship between social support and depression. With this goal, has interviewed a total sample of 1503 persons of adult age (young people, adults and elderly) belonging to Spain, Cuba and Mexico. For the evaluation of the depression, has been used the questionnaire CES-D, while for the assessment of emotional support perceived and satisfaction with the same we applied a formal model of self-evaluation report prepared by us which gathers the perception of availability of emotional support from various sources (partner, family members, friends, colleagues, neighbors) and their satisfaction with the same. The results obtained indicate that the relationship obtained between emotional support according to different sources and values in depressive symptomatology is subject to changes depending on the cultural influences associated to the country of origin of those interviewed, and his age, as well as the interaction between both variables

Afrontamiento psicológico de los procedimientos médicos invasivos y dolorosos aplicados para el tratamiento del cáncer infantil y adolescente: la perspectiva cognitiva conductual / Psychological coping with invasive and painful medical procedures in the treatment of childhood and adolescent cancer: The cognitive-behavioural approach

El afrontamiento psicológico del cáncer infantil implica el uso de estrategias y recursos que ayuden al niño y a su familia a vivenciar la enfermedad con la menor afectación emocional y comportamental posible. En este sentido, desde la Psicología se han desarrollado y adaptado técnicas y programas con el objetivo de minimizar el impacto psicológico que implica el diagnóstico y tratamiento del cáncer en la infancia y la adolescencia. En el presente artículo se revisan los procedimientos psicológicos fundamentados en el paradigma cognitivo-conductual como la transmisión de información, el entrenamiento en habilidades de afrontamiento, el audiovisual, el juego, la biblioterapia y el humor, considerando su aplicación en niños y adolescentes, y el papel de los padres en la preparación (AU)

Psychological coping with childhood cancer involves the use of strategies and resources that help children and their families undergo the disease with the fewest possible emotional and behavioural problems. In the field of Psychology, techniques and programs have been developed and adapted with the aim of minimizing the psychological impact of the diagnosis and treatment of childhood and adolescent cancer. The present paper reviews psychological procedures based on the cognitive-behavioural paradigm, such as transmission of information, coping skills training, the use of audiovisual materials, games, bibliotherapy, and humour. It considers the use of such procedures in children and adolescents and the role of parents in the preparation (AU)

Depresión y envejecimiento: Algunas cuestiones de interés respecto a la investigación epidemiológica / No disponible

En el presente trabajo se revisan algunos de los aspectos de mayor relevancia respecto a la investigación epidemiológica sobre depresión y envejecimiento. En este sentido se abordan las dificultades para la evaluación de la depresión en ancianos, las características específicas de las alteraciones depresivas en las personas de edad avanzada, la influencia del género y del envejecimiento en la formación de trastornos depresivos y la influencia de factores de tiposociocultural sobre la estructura misma de los síndromes depresivos a lo largo del proceso deenvejecimiento. Se termina concluyendo la importancia de considerar estos aspectos para una mejor comprensión de las depresiones a lo largo del desarrollo adulto, al tiempo que se establece un distanciamiento del estereotipo injustificado de ancianidad unida a depresión (AU)

In the present work some of the more important aspect on epidemiologic research about aging and depression are revised. At hits way, the problems in assessment of depression in old people, the specific characteristics of the depressive disorders, the influence of the gender and aging and the influence of cultural factors are studied. Finally, the importance of these topics for a better understanding of depressions along the aging, at the time that a distancing of the unjustified stereotype of old age and depression is indicated (AU)

Implicaciones de la edad y el género respecto a la depresión en ancianos / No disponible

Fundamentos: Nuestro estudio tiene como objetivo delimitar si existe una influencia recíproca entre el género y la edad respecto a la depresión en ancianos. Métodos: La muestra está formada por 237 sujetos mayores de 65 años pertenecientes a la Región de Murcia, 124 mujeres y 113 hombres. Para dicha muestra, se han realizado análisis de varianza y de correlación para el estudio de la relación edad-género-depresión. La muestra se ha dividido en distintos grupos según la edad para analizar el efecto de ésta en la depresión. Resultados: Se ha obtenido una relación estadísticamente significativa entre género y depresión pero no entre edady depresión. Conclusiones: Según nuestro trabajo, ser mujer se asocia a mayores puntuaciones en depresión en los ancianos con independencia de la edad, mientras que la edad no se ha mostrado determinante en la existencia de fluctuaciones en los valores de depresión en la población anciana (AU)

Foundations: The purpose of this study is to identify whether age and gender in elderly people has any influence in their depression. Methods: We have worked with 237 individuals for this survey from 65 years old on wards. They all belong to the Region of Murcia. 124 of them are women and 113 are men. We have carried out analysis of variance and correlation for the study of the relation ship among age, gender and depression.The individuals have been divided in different groups according to their age facilitating the observation of age in depression. Results: A significant relationship has been determined between gender and depression but not between age and depression. Conclusions: As a result we can say that gender - olderwomen - scores higher punctuations in depression with independence of their age. However age has not shown to be decisive in elderly depression (AU)