Featured paper: Additivated perovskites for more stable solar cells.


[Paper: Effect of the incorporation of poly(ethylene oxide) copolymer on the stability of perovskite solar cells. Jeann Carlos da Silva, Francineide Lopes de Araújo, Rodrigo Szostak, Paulo Ernesto Marchezi, Raphael Fernando Moral, Jilian Nei de Freitas  and  Ana Flávia Nogueira. J. Mater. Chem. C, 2020,8, 9697-9706].

"Sandwich" of materials that form the perovskite solar cell developed by the Brazilian team.
“Sandwich” of materials that form the perovskite solar cell developed by the Brazilian team.

Thanks to the contributions of research groups from different countries, perovskite-based solar cells have quickly become competitive in terms of energy conversion efficiency – the percentage of solar energy that is converted into electrical energy – reaching values above 25%. Unfortunately, the good efficiency achieved for these solar cells does not remain throughout their use, mainly because of the instability of their active layer. Composed of materials from the perovskite family, this layer of the sandwich-like solar cell is responsible for absorbing light. Due to moisture, as well as light itself, perovskite degrades and threatens the life cycle of a solar cell.

The problem has been the focus of many researchers in the area, among them, those from the Laboratory of Nanotechnology and Solar Energy (LNES) at Unicamp (Brazil), led by Professor Ana Flávia Nogueira. In recently reported research in the Journal of Materials Chemistry C (impact factor 7.059), LNES members were able to produce more stable perovskite films which allowed manufacturing solar cells with lower efficiency losses over time.

The addition of copolymer P(EO/EP) improved the stability of MAPbI3 perovskite.
The addition of copolymer P(EO/EP) improved the stability of MAPbI3 perovskite.

The strategy adopted was to add to the perovskite a compound that gives it stability without affecting its crystalline structure, from which important properties emerge for solar cell performance. The chosen additive, a copolymer (polymer formed by two different monomers), was added in different concentrations to a solution of lead iodide and methylammonium iodide, which, when crystallized, formed a modified and more stable perovskite film.

The researchers used the spin coating technique to prepare filmes of pure perovskite and “additivated” perovskite. In a material degradation test, the authors exposed the samples to ambient light and humidity for nine days and observed their degradation, which was visible to the naked eye by the yellowing of the films, whose original color is almost black. In the samples with additive, the degradation was delayed by a few days when compared to the pure perovskite samples.

Another test carried out by the team showed the films’ ability to regenerate after an initial degradation caused by exposure to a humidifier. The samples with the additive not only degraded less, but also spontaneously regenerated, almost entirely, thirty seconds after removing the moisture source – a phenomenon known as healing – as can be seen in this video.

“This work demonstrated that incorporating a copolymer based on poly(ethylene oxide) to the perovskite layer can delay and, in some cases, even reverse the degradation process of the film with relation to moisture and lighting,” summarizes Jeann Carlos da Silva, co-author of the article.

box_enTo study in detail the structure and composition of the films, the authors used a series of characterization techniques, including an X-ray diffraction technique (in situ GWAXS), available at the Brazilian National Synchrotron Light Laboratory (LNLS), which allowed to monitor the manufacturing process of the films. Based on the set of characterization results, the authors were able to explain the mechanism that generates the protective effect in perovskite films with additives. According to them, the effect occurs mainly due to the interaction performed by the copolymer, through hydrogen bonds, with the methylammonium cation of the perovskite.  In films without the additive, light and moisture cause part of the methylammonium to shift into the gas state and then leave the perovskite structure, generating the degradation, which is partially irreversible. In the films with the additive, the copolymer retains the methylammonium, which generates films that are more stable and have greater regenerative capacity.

“This study also allowed to investigate the crystallization dynamics of the perovskite containing the copolymer, as well as to understand the formation mechanisms of perovskite/copolymer in humidity and lighting conditions,” highlights Francineide Lopes de Araújo, co-author of the article. “In addition, through characterization techniques such as in situ X-ray diffraction, the study explores an important area in order to understand the material, offering an important contribution to the scientific community and opening new investigation perspectives for the application of polymers in the process of forming and manufacturing perovskite solar cells,” she adds.

Finally, the scientific team manufactured solar cells using perovskite films with and without additives as active layer, and compared their energy conversion efficiency. Initially, the presence of the copolymer decreased the efficiency of the devices, since, as it is an insulating material, it impairs the transfer of electrical charges. However, in the stability tests, when the devices were exposed to humidity and light for twenty days, the perovskite cells with additives performed better.

In numbers: while pure perovskite solar cells started at 17% efficiency and maintained 47% of that value at the end of the test, perovskite devices containing 1.5 mg mL-1% copolymer had an initial efficiency of around 15 %, but retained 68% of efficiency after the 20 days of testing.

“Unfortunately, the problem of stability of perovskite solar cells could not be definitively solved through this research, however, an important way to protect the material was explored, mainly against aggressive exposure to moisture and light, which in the future can be combined with other protection mechanisms,” summarizes Jeann Carlos da Silva. “The research also reinforces the feasibility of incorporating extrinsic compounds to perovskite as protective agents,” he adds.

This study began at LNES in 2016, in the master’s research of Jeann Carlos da Silva, shortly after the development, in that same laboratory, of the first perovskite solar cell prototype in Brazil. The research was completed with the collaboration of the postdoctoral fellow Francineide Lopes de Araújo and other members and former members of the group, always under the guidance of Professor Ana Flávia.

The study was funded by Brazilian agencies FAPESP, CNPq and CAPES, and is the subject of the project “Perovskite Solar Cells for Artificial Photosynthesis” of the Center for Innovation on New Energies (CINE) with support from Shell and Fapesp.

Authors of the paper. From the left: Jeann Carlos da Silva, Francineide Lopes de Araújo, Rodrigo Szostak, Paulo Ernesto Marchezi, Raphael Fernando Moral, Jilian Nei de Freitas and Ana Flávia Nogueira.
Authors of the paper. From the left: Jeann Carlos da Silva, Francineide Lopes de Araújo, Rodrigo Szostak, Paulo Ernesto Marchezi, Raphael Fernando Moral, Jilian Nei de Freitas and Ana Flávia Nogueira.

Tribute from B-MRS member to Prof. Larry Thompson.


[Text by Professor Petrus Santa Cruz (DQF/UFPE), B-MRS member.]

Behind and to the left, Petrus Santa Cruz (UFPE) next to Larry Thompson (UMD). At the front, Osvaldo Serra and Vitória Lakatos (USP) during the 40-year international cooperation “Larry Thompson and Brazil” workshop in 2009 at DQF/UFPE.
Behind and to the left, Petrus Santa Cruz (UFPE) next to Larry Thompson (UMD). At the front, Osvaldo Serra and Vitória Lakatos (USP) during the 40-year international cooperation “Larry Thompson and Brazil” workshop in 2009 at DQF/UFPE.

Some researchers make a difference in contributing for consolidating important areas of Science in Brazil. In the case of Professor Larry Clark Thompson, of the University of Minnesota-Duluth, he will always be remembered not only for his significance in the area of coordination compounds in the country, but also for his generosity. During the workshop “Larry Thompson and Brazil” held to celebrate 40 years of international cooperation in 2009, the beginning of his contributions to Brazilian science in 1970 was remembered, when he received professors Gilberto Sá (DQF/UFPE) and Oswaldo Serra (USP/Ribeirão Preto) in his group in the USA, resulting in collaborations that extended throughout his academic life.

Over the past 50 years, several episodes have been marked by his generosity.

In 2002 Professor Thompson participated in a thesis panel at DQF/UFPE on pioneering works in exploring the degradation of lanthanide complexes, which resulted in an innovative dosimeter device for measuring UV radiation, but before participating in the panel, Thompson hosted the doctoral student at his residence in Minnesota -Duluth, so that she could show him in his laboratory that the complexes actually degraded under the action of UV radiation, giving rise to a new line of research on devices for the prevention of skin cancer, currently explored for individual monitoring of vitamin D in a project of the Sibratec Nano program. Several other applications use as an active part the luminescent materials derived from his work.

Thompson was in Brazil for the last time in 2017, but unfortunately this year circumstances prevented the workshop “Larry Thompson and Brazil” of the 50 years of collaborations. He passed away at the age of 85 on August 15th, leaving behind many memories.

Call for thematic symposia of the B-MRS + IUMRS event on materials research is open until November 11th.


The Brazilian Materials Research Society (B-MRS/ SBPMat) and the International Union of Materials Research Societies (IUMRS) invite the scientific community to submit symposium proposals for the joint event on materials research that will take place from August 29 to September 2, 2021.

logo2021b_400pxSymposium proposals can be submitted until November 2   11, for the event that will bring together the XIX B-MRS Meeting (B-MRS annual event) and the IUMRS – ICEM (seventeenth edition of the international conference on electronic materials organized every two years by IUMRS).

The event, initially scheduled to take place in 2020, was postponed due to the pandemic, and will be held from August 29 to September 2, 2021. The place remains the same: the Rafain Palace Hotel and Conventions, located in Foz do Iguaçu, a tourist Brazilian city close to the border with Argentina and Paraguay, which serves as a base for visits to Iguassu Falls and other attractions in the surroundings.

Symposium proposals can be submitted by teams of researchers, preferably of international composition, who wish to organize a thematic symposium within the event. Proposals that had been submitted and approved for the 2020 event are also expected to be resubmitted. “All symposium proposals will need to be sent by the deadline, including those that had been accepted for the 2020 event”, reinforces Professor Gustavo Dalpian, chair of the event. “The organizers of the symposia that had previously been approved will notice, when accessing the system, that the data from the 2020 proposal was automatically copied to the 2021 event. In this way, the organizers will be able to make the necessary adjustments and resubmit, but without having to enter everything again ”, he completes.

As in all editions of the B-MRS Meeting, the event will cover a wide range of topics in Materials Science and Technology, with a special emphasis on electronic materials, due to IUMRS-ICEM. Therefore, proposals for symposia are welcome on topics related to all types of materials, from design and synthesis to applications.

To submit a symposium proposal, just fill in English the form, available online at http://sbpmat.org.br/proposed_symposium/.

The symposia will be the main focus of the event along with plenary lectures, which will feature internationally renowned scientists who have already confirmed their presence: Alex Zunger (University of Colorado Boulder, USA), Edson Leite (LNNano, Brazil), Hideo Hosono (Tokyo Institute of Technology, Japan), John Rogers (Northwestern University, USA), Luisa Torsi (Università degli Studi di Bari “A. Moro”, Italy), Tao Deng (Shanghai Jiaotong University, China) and Thuc-Quyen Nguyen (University of California Santa Barbara, USA). The traditional Memorial Lecture “Joaquim da Costa Ribeiro” will be given by Cid Bartolomeu de Araújo (UFPE, Brazil).

Symposium proposals will be evaluated by the event committee, and, by the end of 2020, the list of approved symposia will be released. On February 1, 2021, the call for papers will be opened, for abstract submission within the thematic symposia. The symposium organizers will be responsible for the evaluation of the submitted abstracts and for the symposium schedule.

The joint event XIX B-MRS Meeting + IUMRS ICEM 2021 is coordinated by professors Gustavo Martini Dalpian (UFABC) in the general coordination, Carlos Cesar Bof Bufon (LNNANO) in the program coordination and Flavio Leandro de Souza (UFABC) as general secretary. The international committee comprises scientists from America, Asia, Europe and Oceania.

The latest editions of the B-MRS Meeting brought together between 1,100 and 2,000 participants from various countries around the world presenting their works within the symposia.

Go to the event website: https://www.sbpmat.org.br/19encontro/.

Cataratas do Iguaçu. By Martin St-Amant (S23678) - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3946052
Cataratas do Iguaçu. By Martin St-Amant (S23678) – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3946052

Postdoctoral positions in Biophotonics at CEPOF/ USP.


POSTDOCTORAL POSITIONS (Four positions available) Center for Research in Optics and Photonics – CEPOF University of São Paulo Brazil

CEPOF is looking for excellent and motivated candidates of any nationality with experience in BIOPHOTONICS, in one or more topics of interest, as:

– Advances in Photodynamic Therapy

– Microorganisms control using photonic strategies

– Photobiomodulation

– Photoimunotherapy for targeting cancer and microorganisms

– New photosensitizers for PDT from natural molecules

– Organic synthesis and photocatalyzed reactions

– Digital agriculture (methods and sensors)

– Food safety using photonic techniques

– Quantum biophotonics

– Microscopy and spectroscopy techniques

– Optical instrumentation for medical devices

– Artificial intelligence, Imaging and data analysis

A full list of research projects can be found at http://cepof.ifsc.usp.br

The candidate will develop research in one of the laboratories of CEPOF.

The projects aim to investigate innovative aspects in Biophotonics for designing new optical applications and instrumentation in Life Sciences. We expect to generate new knowledge in the topics of interest.

The candidate must have obtained PhD degree in Physics, Biology, Engineering, Chemistry, Computational Sciences, Biomedical Sciences or related areas, during the past 5 years.

Necessary documents (to be sent by email: cristina@ifsc.usp.br):

– Two recommendation letters

– CV with list of publications and expertise

– One-page letter of interest (the specific topic(s) of interest must be clear)

– Name and contact information of the providers of the recommendation letters.

Application deadline: October 10th, 2020

Candidates selection will be done by the faculties of the CEPOF.

Selected candidates are expected to start the postdoctoral fellow in January – February, 2021. The selected candidate will receive a Post-Doctoral fellowship from the São Paulo Research Foundation (FAPESP) in the amount of R$ 7,373.10 monthly and a research contingency fund, equivalent to 15% of the annual value of the fellowship which should be spent in items directly related to the research activity.

Unpaid researchers: Olivia Carr.


Olivia: back at her parents’ house after having developed a sensor for early detection of disease.

Olívia Carr at the lab during her doctorate at the end of 2018.
Olívia Carr at the lab during her doctorate at the end of 2018.

Head and neck cancer affects thousands of Brazilians every year. About 60% of these people are diagnosed late, which reduces their quality of life and makes treatment difficult. In her PhD in Materials Science and Engineering, carried out at USP, Olivia Carr generated a low-cost sensor that can detect the propensity of a person developing this cancer.

Olivia’s work was highlighted on the cover of a renowned international scientific journal (Talanta), in addition to generating a patent application, as well as other published articles. And furthermore, the technology developed in this work could be adapted to detect other diseases, including Covid-19.

Olivia, who is 30 years old, wants to continue contributing to society through research, which is the professional activity she most enjoys doing and for which she trained for over a decade. However, since the end of her doctorate, November of last year, she has only seen doors and opportunities closing.

Initially, she received, with great enthusiasm, three proposals to carry out post-doctoral studies in company projects, but two of them did not come through due to the pandemic (the companies decided not to make this investment in light of the new scenario) and the third did not succeed for other reasons. The young PhD then participated in a call from CNPq (the main Brazilian federal research funding agency) for projects related to the fight against Covid-19, in which she would receive a scholarship. However, her project was not approved for funding. After these initial frustrations, Olivia continued to participate in selection processes in research institutions and sent her resume to companies in Brazil that have a research and development area. Unfortunately, this path was not successful.

In parallel, in order to remain active and continue her career, she has worked with old and new collaborators, writing scientific articles and an academic book chapter for publication. All without receiving any payment, which is why she had to return to her parents’ house in the city of Rio Claro, which she had left to do her doctorate in São Carlos.

But it is not the first time that Olivia has experienced financial constraints in order to do research. In the four years of her doctorate, she spent more than half of that time without a scholarship. And here it is noteworthy to clarify that it is wrong to think that a doctoral student receives a scholarship to have more time for study or leisure. The doctorate is, in most cases, a full-time activity, which includes both the student’s theoretical training (the subjects taken) and the practical training (the doctoral research). Moreover, doctoral research is, in addition to training, a complete scientific undertaking, with results that contribute to the advancement of world science and industrial innovation.

Thus far, Olivia has not given up being a researcher, a profession that captivated her at the end of her undergraduate degree in Physics, when she discovered the day-to-day life of a research laboratory. However, after 10 months without pay, this science professional, trained to develop devices that can have great impact on people’s health, has started to evaluate other options, such as teaching Physics.

 

Postdoctoral Fellowship at UNESP.


posdoc unesp*Opportunity: the Laboratory of Nanostructured Materials for Environmental and Biological Analyses invites applications for a post-doctoral research fellowship funded by São Paulo Research Foundation (FAPESP: https://www.fapesp.br/en). This fellowship is linked to the Thematic Project “Toward a convergence of technologies: from sensing and biosensing to information visualization and machine learning for data analysis in clinical diagnosis” (FAPESP process number: 2018/22214-6).

*Supervisor: Carlos José Leopoldo Constantino (full professor).

*Institution: Department of Physics, São Paulo State University (UNESP), campus in the city of Presidente Prudente, São Paulo State, Brazil (https://www.international.unesp.br/).

*Fellowship components: it includes a monthly stipend (R$ 7,373.10) and research contingency funds (15 per cent of the annual value of the fellowship for using in activities developed by the Fellowship holder, strictly related to the fellowship research project).

*Duration of the post-doctoral fellowship: up to 48 months (starting: December/01/2020 or as soon as possible; ending: up to February/28/2025).

*More info/fellowship: https://www.fapesp.br/en/postdoc

*Candidate requirements: she or he should have concluded the Ph.D. less than seven years before the beginning of the post-doctoral fellowship. Applicants must have a Ph.D. in physics, chemistry, materials science or related fields. The successful candidate must have excellent communication skills and excel in a highly collaborative research environment. In addition to the timely publication of research results in peer-reviewed journals, the responsibilities of the post-doctoral include drafting progress reports. The successful candidate will conduct research on: Detection of pesticides using surface-enhanced Raman scattering (SERS) spectroscopy. Therefore, this research includes experimental activities using techniques such as:

(i) Synthesis of colloid of metallic nanoparticles applied as “SERS substrate”.

(ii) Characterizations of the “SERS substrates” through microscopy, UV-Vis extinction spectroscopy, zeta potential, and dynamic light scattering (DLS).

(iii) Micro-Raman and surface-enhanced Raman scattering (SERS) spectroscopies.

(iv) Computational methods for data analysis.

*Deadline for application: October/13/2020.

*Application: interested individuals should send to carlos.constantino@unesp.br the following documents:

(i) CV with the list of publications.

(ii) Two letters of recommendation.

(iii) Work plan: 4-pages maximum with title, justification, objectives, and methodology.

Available facilities (basic):

https://www.fct.unesp.br/#!/departamentos/fisica-quimica-e-biologia/laboratorios/