Fabrication of solution-processed perovskite solar cells (PSCs) requires the deposition of high quality films from precursor inks. Frequently, buffer layers of PSCs are formed from dispersions of metal oxide nanoparticles (NPs). Therefore, the development of trustable methods for the preparation of stable colloidal NPs dispersions is crucial. In this work, a novel approach to form very compact semiconducting buffer layers with suitable optoelectronic properties is presented through a self-functionalization process of the nanocrystalline particles by their own amorphous phase and without adding any other inorganic or organic functionalization component or surfactant. Such interconnecting amorphous phase composed by residual nitrate, hydroxide, and sodium ions, proved to be fundamental to reach stable colloidal dispersions and contribute to assemble the separate crystalline nickel oxide NPs in the final film, resulting in a very homogeneous and compact layer. A proposed mechanism behind the great stabilization of the nanoparticles is exposed. At the end, the self-functionalized nickel oxide layer exhibited high optoelectronic properties enabling perovskite p-i-n solar cells as efficient as 16.6% demonstrating the pertinence of the presented strategy to obtain high quality buffer layers processed in solution at room temperature.

Effective control of the interface between the metal cathode and the electron transport layer (ETL) is critical for achieving high performance p-i-n planar heterojunction perovskite solar cells (PSCs). Several organic molecules have been explored as interlayers between the silver (Ag) electrode and the ETL for the improvement in the photovoltaic conversion efficiency (PCE) of p-i-n planar PSCs. However, the role of these organic molecules in the charge transfer at the metal/ETL interface and the chemical degradation processes of PSCs has not yet been fully understood. In this work, we systematically explore the effects of the interfacial modification of the Ag/ETL interface on PSCs using rhodamine 101 as a model molecule. By the insertion of rhodamine 101 as an interlayer between Ag and fullerene derivatives (PC60BM and PC70BM) ETLs improve the PCE as well as the stability of p-i-n planar PSCs. Atomic force microscopy (AFM) characterization reveals that rhodamine passivates the defects at the PCBM layer and reduces the band bending at the PCBM surface. In consequence, charge transfer from the PCBM towards the Ag electrode is enhanced leading to an increased fill factor (FF) resulting in a PCE up to 16.6%. Moreover, rhodamine acts as a permeation barrier hindering the penetration of moisture towards the perovskite layer as well as preventing the chemical interaction of perovskite with the Ag electrode. Interestingly, the work function of the metal cathode remains more stable due to the rhodamine incorporation. Consequently, a better alignment between the quasi-Fermi level of PCBM and the Ag work function is achieved minimizing the energy barrier for charge extraction. This work contributes to reveal the relevance of proper interfacial engineering at the metal-cathode/organic-semiconductor interface.

While perovskite solar cells (PSCs) have been developed with different device architectures, mesoporous devices have provided the highest power conversion efficiencies. In this work, the working mechanism of both positive-intrinsic-negative (p-i-n) and negative-intrinsic-positive (n-i-p) meso-superstructured (MSSC) PSCs, which include a thin interlayer of porous alumina at the bottom electrode, is explored. Interestingly, for both p-i-n and n-i-p architecture, the mesoporous configuration was more efficient than its planar counterpart. For MSSC SnO 2 -based n-i-p devices, that result was primarily due to an increase in V oc and J sc , resulting from improved band alignment and filling of the electron trap states (n-doping at the SnO 2 /perovskite interface), which led to devices with 21.0% efficiency and 20.3% stabilized power output (SPO). Although MSSC NiO x -based p-i-n meso-superstructured devices were less efficient due to lower V oc , a slightly higher J sc and fill factor improvement was achieved by the Al 2 O 3 mesoporous layer, resulting in devices with 16.9% efficiency. Importantly, the electronic nature of the perovskite is dependent upon its physical confinement within a mesoporous scaffold. Therefore, either p-or n-type semiconductor/perovskite interfaces can be engineered by selectively modifying the semiconductor behavior with the introduction of an insulating mesoporous scaffold interlayer.

Optimization of the interface between the electron transport layer (ETL) and the hybrid perovskite is crucial to achieve high-performance perovskite solar cell (PSC) devices. Fullerene-based compounds have attracted attention as modifiers on the surface properties of TiO, the archetypal ETL in regular n-i-p PSCs. However, the partial solubility of fullerenes in the aprotic solvents used for perovskite deposition hinders its application to low-temperature solution-processed PSCs. In this work, we introduce a new method for fullerene modification of TiO layers derived from nanoparticles (NPs) inks. Atomic force microscopy characterization reveals that the resulting ETL is a network of TiO-NPs interconnected by fullerenes. Interestingly, this surface modification enhances the bottom interface of the perovskite by improving the charge transfer as well as the top perovskite interface by reducing surface trap states enhancing the contact with the p-type buffer layer. As a result, rigid PSCs reached a 17.2% power conversion efficiency (PCE), while flexible PSCs exhibited a remarkable stabilized PCE of 12.2% demonstrating the potential application of this approach for further scale-up of PSC devices.

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3 ResumenAntecedentes: el etiquetado nutricional es una herramienta para que los consumidores tomen decisiones respecto a su alimentación, para conservar la salud y prevenir enfermedades. Objetivos: describir la asociación entre variables sociodemográficas con la lectura de las etiquetas e identificar la percepción de los compradores en torno al etiquetado nutricional de alimentos. Metodología: se utilizó por triangulación de métodos; desde lo cuantitativo, se realizó un estudio descriptivo en una muestra de 384 personas. Desde lo cualitativo, se utilizó la perspectiva de etnografía enfocada; se realizaron 30 entrevistas a compradores de alimentos y 20 observaciones en el momento de la compra. Resultados: se encontró asociación (p<0,005) entre variables sociodemográficas, como género, nivel de estudios y ocupación y la lectura de la etiquetado nutricional. Desde el componente cualitativo se resalta cómo los consumidores presentan un bajo nivel de información sobre el etiquetado nutricional y tienen dificultades para interpretarlo. La selección y compra de alimentos no se hace por la información nutricional sino por motivos como tradición y sabor. Conclusiones: el desconocimiento sobre el etiquetado nutricional no contribuye al proceso de selección y compra de los alimentos, otros aspectos de tipo personal y cultural determinan la decisión de compra de alimentos.Palabras clave: etiquetado de alimentos, etiquetado nutricional, información nutricional, educación alimentaria y nutricional. Etiquetado nutricional, una mirada desde los consumidores de alimentos AbstractBackground: Nutritional labeling is a consumer's tool when it comes to taking decisions about their nutrition, for the health maintenance and prevention of disease. Objective: to describe the association between sociodemographic variables, upon reading the labels and identify the consumer's perception about nutritional labeling. Materials and methods: A triangulation of methods were used; from a quantitative methodology, descriptive study was conducted on a sample of 384 persons. From a qualitative methodology, a focalized ethnography approach was used, 30 interviews were conducted, and 20 observations at the time of the purchasing food. Results: An association was found of (p<0,005) between sociodemographic variables such as: gender, educational level, occupation and the lecture of the nutritional label. From a qualitative component, consumers have a low level of information on the nutritional label and the difficulty interpreting it. The selection and purchase of food is not based on a nutritional basis but rather on reasons such as taste or tradition. Conclusions: The lack of knowledge about nutritional labeling, does not contribute to the process of selection and purchase of food. Other aspects such as personal and cultural are what determine the purchasing decision of consumers.

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