In situ ethanolamine ZnO nanoparticle passivation for perovskite interface stability and highly efficient solar cells

Zinc oxide (ZnO) has interesting optoelectronic properties, but suffers from chemical instability when in contact with perovskite interfaces; hence, the perovskite deposited on the top degrades promptly. Surface passivation strategies alleviate this instability issue; however, synthesis to passivate ZnO nanoparticles (NPs) in situ has received less attention. Here, a new synthesis at low temperatures with an ethanolamine post treatment has been developed. By using ZnO NPs prepared with ethanolamine and butanol (BuOH), (E-ZnO), the stability of the FA0.9Cs0.1PbI3 (FACsPI)–ZnO interface was achieved, with a photoconversion efficiency of >18%. Impedance spectroscopy demonstrates that the recombination at the interface was reduced in the system with E-ZnO/perovskite compared to common SnO2/perovskite and that the quality of the perovskite on the top is clearly due to the ZnO in situ passivation with ethanolamine. This work extends the use of E-ZnO as an n-type charge extraction layer and demonstrates its feasibility with methylammonium perovskite. Moreover, this study paves the way for other in situ passivation methods with different target molecules, along with new insights regarding the perovskite interface rearrangement when in contact with the modified electron transport layer (ETL)

Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

Formamidinium‐based perovskite solar cells (PSCs) present the maximum theoretical efficiency of the lead perovskite family. However, formamidinium perovskite exhibits significant degradation in air. The surface chemistry of PbS has been used to improve the formamidinium black phase stability. Here, the use of PbS nanoplatelets with (100) preferential crystal orientation is reported, to potentiate the repercussion on the crystal growth of perovskite grains and to improve the stability of the material and consequently of the solar cells. As a result, a vertical growth of perovskite grains, a stable current density of 23 mA cm−2, and a stable incident photon to current efficiency in the infrared region of the spectrum for 4 months is obtained, one of the best stability achievements for planar PSCs. Moreover, a better reproducibility than the control device, by optimizing the PbS concentration in the perovskite matrix, is achieved. These outcomes validate the synergistic use of PbS nanoplatelets to improve formamidinium long‐term stability and performance reproducibility, and pave the way for using metastable perovskite active phases preserving their light harvesting capability

The impacts of the food, fuel and financial crises on households in Nigeria. A retrospective approach for research enquiry

This paper examines the impacts of the financial, food and fuel crises on the livelihoods of low-income households Nigeria. It uses primary household level data from Nigeria to analyse the impacts of induced price variability on household welfare. Our results indicate that aggregate shocks have significant adverse effects on household consumption, human capital, and labour decisions with a degree of impact variability between northern and southern regions of the country. We find that the coping strategies adopted by the poor to deal with the short-term effects of the crises, and which include substitution for lower quality food, increasing the intensity of work, withdrawing children from school – especially girls – and engaging children in child labour, can lock households in a low-income equilibrium or poverty trap. Provided that covariate shocks exacerbate these effects, tackling the effects of covariate risks becomes central for present and future development policy

Social Assistance in Developing Countries Database Version 5.0

The Social Assistance in Developing Countries Database is a user-friendly tool that provides summary information on social assistance interventions in developing countries. It provides a summary of the evidence available on the effectiveness of social assistance interventions in developing countries. It focuses on programmes seeking to combine the reduction and mitigation of poverty, with strengthening and facilitating household investments capable of preventing poverty and securing development in the longer term. The inclusion of programmes is on the basis of the availability of information on design features, evaluation, size, scope, or significance. Version 5 of the database updates information on existing programmes and incorporates information on pilot social assistance programmes in Latin America, Asia and Africa. It also adopts a new typology that distinguishes between social assistance programmes providing pure income transfers; programmes that provide transfers plus interventions aimed at human, financial, or physical asset accumulation; and integrated poverty reduction programmes. This new typology has, in our view, several advantages. It is a more flexible, and more accurate, template with which to identify key programme features. It provides a good entry point into the conceptual underpinnings of social assistance programmes

Resilience and Livelihoods; A community development model

Objective: To formulate a community development model to contribute to rural resilience in the states of Campeche, Chiapas, Tabasco, Yucatan and Quintana Roo, Mexico. Design/methodology/approximation: The execution of the project considered the incursion into communities of high and very high marginalization with a population of 300 to 3,800 inhabitants established in five states during the period July 2017 to March 2018, under the auspices of INCA Rural, A.C.. Sustainable livelihoods and the logical framework made it possible to systematize and analyze data collected in the characterization of the development potential of the territory (natural resources, productive resources and anthropogenic activity), carried out with literature review and field phase. A social innovation agenda was formulated with descriptive cards of projects and potential sources of financing. Results: 93 localities established in 14 microregions in five states were intervened, 90 extension agents in community development were trained, 216 training actions carried out, 90 community databases, 90 community development plans, 90 acts of integration of órganos de consulta y planeación comunitaria (OCPC) and 14 records of integration of grupos de extensionismo para el desarrollo microrregional (GEDM). Limitations on study/implications: The duration of the project prevented the implementation of the community development plan. Findings/conclusions: The present model preponderates the active participation of the individual as the basis for contributing to the improvement of the quality of life of the community, based on the valorization of the territory and the collective identity framed in participatory processes.Objective: Formulate a community development model to contribute to rural resilience at the states of Campeche, Chiapas, Tabasco, Yucatán and Quintana Roo, Mexico.Design/methodology/approach: The project execution considered the incursion in high and very high marginalization communities with populations between 300 and 3,800 inhabitants, throughout five states. Sustainable livelihoods and the logical framework made it possible to systematize and analyze the collected data to characterize the potential territorial development, carried out with a secondary sources review and a field phase. A social innovation agenda was formulated with descriptive files of projects and potential financing sources.Results: 93 localities established in 14 micro-regions in five states were intervened. Ninety extension workers were trained in community development, 216 training actions took place, 90 community databases compiled, 90 community development plans, 90 integration acts of community consultation and planning bodies (CCPB) and 14 acts of integration of extension groups for the microregional development (EGMD).Limitations of the study/implications: The duration of the project prevented the implementation of community development plans.Findings/conclusions: The present model consider the individuals participation as the basis for the life quality improvement of the community, based on territorial appreciation and the collective identity framed in participatory processes

Effect of Different Sensitization Technique on the Photoconversion Efficiency of CdS Quantum Dot and CdSe Quantum Rod Sensitized TiO2 Solar Cells

The procedure employed for the sensitization of mesoporous photoanodes affects strongly the final performance of sensitized devices, especially when semiconductor quantum dots and quantum rods are used as sensitizers. In this work the effect of three different sensitizing methods in the final cell performance was analyzed. The TiO2 films were sensitized with CdS QDs grown by successive ionic layer adsorption and reaction, SILAR, and with CdSe quantum rods deposited by electrophoretic and pipetting methods. Several configurations of the sensitizers and combinations of sensitization methods were tested. 4% photoconversion efficiencies were obtained for TiO2 electrodes sensitized with CdS and CdSe by electrophoretic and pipetting respectively, while for the sensitizer with both techniques the efficiency was 4.7%. This high efficiency is mainly due to the high fill factor (60%) and the photocurrents (13.1 mA/cm2) obtained by the correct combination of near-infrared and visible light photoabsorption, the better CdSe QRs distribution in the TiO2 film and a passivation of the TiO2 nanocrystals. Electrochemical impedance measurements has been analyzed and discussed in detail providing a detailed analysis of recombination resistance and charge transport processes. These parameters have been correlated with the cell performance.We acknowledge fi nancial support from CONACYT through Grant 134111, the UC-MEXUS program Grant 00007, CIO- UGTO 2013-2015, and the CEMIE-Solar (04002) consortium. D.E. and A.C.-P. acknowledge scholarships from CONACYT, I.Z. acknowledges CONACYT for the postdoctoral fellow, and thanks are given to Maria Christian Albor for SEM and EDS analysis