Author: SD

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Sourabh Pal, Indian Institute of Technology, Kharagpur, India. Email id: sourabhelt92@gmail.com (24^th September, 2020 08:30 IST)

KOLKATA: Portable electronic devices have now become an indispensable part of our life. The conventional electronic systems pervade in every aspect of human life, whether it is mobile phones, televisions, computers, or medical instruments, and many more. Most of electronic devices has been conquered by optoelectronics which can offer the purposes that are not possible with simple electronics. They can transmit information to a much longer distance at a significantly higher rate. Optoelectronic devices engage those electronic devices that engender light, control light, and convert optical signals into electrical ones. Optoelectronics has become the subject matter of extensive research in recent years, leading to the development of various commercial products, such as light emitting diodes (LEDs) for home lightning and display panel in television, semiconductor lasers as emitters, and photodiodes as detectors for application in communication, medical and defense and solar cells as a renewable energy source for electricity production.

While many of these optoelectronic devices are very well developed and industrially feasible, more fundamental research is required to improve their efficiency and reduce the cost. In the past few decades, inorganic materials such as silicon and III-V compound semiconductors are widely used in manufacturing the aforementioned optoelectronic devices. However, complex manufacturing processes of such devices lead to a higher production cost. Additionally, the high temperature fabrication steps required in the manufacturing process of inorganic devices creates several difficulties for industrializations. Hence, as a savior of current research society, the researchers have discovered a new class of semiconducting materials: the hybrid organic inorganic metal halide perovskites which have been extensively explored for application in optoelectronic devices owing to the extraordinary electrical and optical properties. These materials are expected to benefit from the striking features of both inorganic and organic materials, such as high charge carrier mobility and low temperature processing possibility. The research on perovskite based devices has experienced rapid growth since the last decade.

The perovskite (CaTiO₃) is a kind of mineral, which was first identified by Russian mineralogist Gustav Rose in 1839 while performing mineralogical studies at Ural mountains. The mineral was named “perovskite” in the honor of Russian mineralogist Count Lev Aleksevich Von Perovski (1792–1856)[1]. Thereafter, the materials with the crystallographic structure similar to the CaTiO₃, like ABX₃ are referred to as perovskite. Here ‘A’ denote positively charged large atomic or molecular cations situated at the center of the cube, ‘B’ atoms also of positive charges located at the corners of the cube, and X is an anion (negatively charged) smaller in size, placed at the faces of the cube. The fascinating properties such as ambipolar charge transport, high charge mobility, large absorption coefficients, band-gap tunability, lower exciton binding energy, large diffusion length resulted in the incredible attention in perovskites and their promising applications, ranging from solar cell, novel lasers, photo detectors to field effect transistors among others. During the past few years, it has been observed that the conventional perovskite based materials exhibit excellent photoluminescence quantum yields with tunable light emission property over the entire visible spectral range. Utilizing these exciting luminescence properties, Prof. Zheng and his group from Nanjing University of Science and Technology, China fabricated highly efficient LED devices in 2015, from which the new era of quantum LEDs (QLED) has been commenced [2]. The gradual increment of the efficiency of electricity-driven LEDs has been updated every year, which makes the practical application much more feasible. Prof. Wang and a research team of Penn State researchers made the discovery while synthesizing perovskite materials for use in next generation solar cells [3]. Perovskites with a crystal structure good at absorbing visible light are an area of focus in developing both rigid and flexible solar cells that can compete commercially with traditional cells made with silicon. These 2D perovskite materials are cheaper to fabricate than silicon and can be equally efficient at absorbing sunlight. The material offers power conversion efficiencies similar to silicon solar cells but can also be used to develop flexible semi-transparent and light-weight cells appropriate for applications in buildings and a variety of urban spaces. In 2019, a group of Steve Albrecht from Helmholtz Young Investigator Group (YIG) at HZB (Helmholtz-Zentrum Berlin) and Bernd Stannowski from the HZB Institute PVcomB (Competence Centre Photovoltaics Berlin) have developed a tandem solar cell made of the semiconductors perovskite and silicon that converts 29.15 per cent of the incident light into electrical energy [4]. These are the highest recorded values reported for scalable perovskite solar cells. Recently, NASA stated that a quick way to secure a reliable supply of electricity for an extended stay on the Moon or Mars would use an ink-jet-like printer to make super-thin solar cells from perovskites [5]. This can undoubtedly open up a new pathway towards science and technology. Hence, the remarkable potential demonstrated by the perovskites could lead to a breakthrough in optoelectronics technology. Innovative research on perovskite based devices would further contribute towards the development of a sustainable and accessible electronic world.

Sources:

1. “Perovskite: Name Puzzle and German-Russian Odyssey of Discovery” by Eugene A. Katz; DOI: 10.1002/hlca.202000061.
2. “Quantum Dot Light-Emitting Diodes Based on Inorganic Perovskite Cesium Lead Halides (CsPbX3 )”, Adv. Mater. 2015, 27, 7162–7167; DOI: 10.1002/adma.201502567.
3. “Distinct conducting layer edge states in two-dimensional (2D) halide perovskite”, Science Advances, 2019; 5 (7); DOI: 10.1126/sciadv.aau324.
4. “Highly efficient monolithic perovskite silicon tandem solar cells: analyzing the influence of current mismatch on device performance”, Sustainable Energy & Fuels, 2019, 3, 1995–2005; DOI: 10.1039/c9se00120d.
5. “Building Solar Panels in Space Might be as Easy as Clicking Print”, NASA; Website: www.nasa.gov/feature/glenn/2019/building-solar-panels-in-space-might-be-as-easy-as-clicking-print.

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Aakash Hossain, School of Materials Sciences and Nanotechnology, Jadavpur University (23^rd September, 2020 08:30 IST)

KOLKATA: The advent of nuclear science and production of atomic energy was started in India under the initiative of a group of scientists led by physicist Dr. Homi Jehangir Bhabha (often referred as “The Indian Oppenheimer”) shortly after the independence of India on 15th August’ 1947. This led to the formation of the Atomic Energy Act in 1948, which created the Indian Atomic Energy Commission, whose purpose was to develop and control the atomic energy to fulfil the necessities connected with it. During that time, the Prime Minister of India, Jawaharlal Nehru believed that India’s nuclear program primarily to be focussed on peaceful applications and not for the creation of any weapons [1]. Although, he later opened the doorway for using nuclear energy to create weapons, for which the nation was compelled to do so. India also opposed the Baruch Plan of the United States [2], which proposed an American monopoly on the control of nuclear energy, on the grounds that such a plan restricted national research and development of atomic energy.

In 1954, the construction of the Bhabha Atomic Research Centre (BARC) at Trombay led to the serious development of India as a nuclear power and eventually BARC became the primary research centre for India’s nuclear energy program. In 1955, Canada collaborated with India by providing a nuclear reactor based on the National Research Experimental Reactor (NRX) at Chalk river, Ontario[3]. The Canada-India Reactor Utility Services (CIRUS) was established thereafter, which completed the project in July 1960. However, most of the plutonium grade weapons, which were produced by CIRUS, were used for India’s first nuclear test. A further agreement was signed at that time with the United States government for providing 21 tons of heavy water for the reactor under the “Atoms for Peace” program ^[4]. Later on, India designed a pool type reactor in 1955, for which United Kingdom Atomic Energy Authority used to supply uranium fuel elements ^[5]. The reactor named as Apsara, was inaugurated by Jawaharlal Nehru in 20^th January 1957 ^[6]. Finally, in 1958, a third reactor was designed in Trombay, named as ZERLINA (Zero Energy Reactor for Lattice Investigation and New Assemblies) which was commissioned in 1961^[7].

In February 1965, Dr. Bhabha visited Washington DC seeking for an American collaboration through the project Plowshare program, in which India could initiate peaceful nuclear explosions to test her nuclear weapons. But at the end, America went against this nuclear co-operation with India. In the year 1966, physicist Dr. Raja Ramanna took charge as the head of BARC after Dr. Bhabha’s death in a plane crash and became the principal designer behind India’s first nuclear device. India wanted to eliminate the western interference in her journey towards being a nuclear power. In the year 1968, India refused to sign the Nuclear Non-Proliferation Treaty (NPT) which could not differentiate between military and peaceful nuclear explosion and it only recognised the United States, Britain and Soviet Union as nuclear weapon states. In September 1972, under the leadership of Dr. Raja Ramanna and with the approval of Prime Minister, Indira Gandhi, India got the approval for testing her first nuclear device. Finally, on 18th May 1974, BARC tested the first nuclear explosive device weighing 3000 pounds and creating an energy surge equivalent to 8 kilotons of TNT. A team of 75 scientists were involved in the designing of the plutonium device. The test, officially known as Pokhran I, was very often referred as the “Smiling Buddha” ^[8]. After this test, India lost her support from Canada and the United States of America, who considered it as a violation of the “Atoms for Peace” program. After 1974, India had to face difficulties in procuring nuclear materials from a suddenly hostile international market. Almost two decades went by for preparing a nuclear arsenal which was capable of military deployment. The BARC leadership, after facing all the challenges, constructed its largest nuclear plant till date which is the Dhruva reactor in 1977 at Trombay which reached its full potential by 1988. Consequently, the Defence Research and Development Lab (DRDL) designed short range (Prithvi) and long range (Agni) missiles both of which were equipped with nuclear warheads. During the regime of Prime Minister Atal Behari Vajpayee, India officially became a nuclear state. Five nuclear devices were tested on May 11th 1998 under the Pokhran II series during the period of physicist Dr. Rajagopala Chidambaram as head of BARC. Although not all of them detonated, the energy surge created was equivalent to 45 kilotons of TNT (16 kilotons according to independent sources). After this massive success, India established the National Security Advisory Board, where a no first-use-policy was devised for Indian nuclear weapons. But it was later amended that if any biological or chemical attack initiated against India, these nuclear weapons can be used. In 2005, India signed a civil nuclear agreement with the United States of America, by which India got an access to buy nuclear materials through international suppliers in exchange of which India has to protect the civilian nuclear facilities, which also includes inspection by the International Atomic Energy Agency [9]. To this day, the prime minister of India, Narendra Damodar Modi chairs the Nuclear Command Authority to call for a nuclear strike. The estimated nuclear warheads possessed by India at present are 135. Henceforth, for every Indian it is a matter of pride that India has achieved and still continues to achieve milestones in nuclear research, which not only makes Indian military strong but is also playing an important role in the daily lives of ordinary civilians.

References- 

1. International nuclear programs- Indian Nuclear program. Atomic Heritage Foundation
2. The Baruch Plan by Bernard Baruch (June 1946). Atomic Heritage Foundation
3. 50 year old Research N-Reactor shut down. Outlookindia.com/newswire
4. Eisenhower’s Atoms for Peace program-Nuclear Power Today. Atomic Heritage Foundation
5. “India’s First atomic reactor- Science Notes and News” . Current science. August 1956. Retrieved 3rd September 2017
6. “Apsara Nuclear Reactor”- NTI Nuclear Security Index. Retrieved 12th April 2015. Archived 19th April 2015
7. “Atomic Research for Asian Welfare”- Press Information Bureau of India. Archived from the original from August 8th 2017 
8. “Bhabha’s quest for the bomb” by George Perkovich- Bulletin of the Atomic Scientists. Vol. 56 No. 3. Pages 54-63 
9. U.S.- India: Civil Nuclear Cooperation. Archive of the U.S. Department of State.

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Sayan Bayan, S. N. Bose National Centre for Basic Sciences, Kolkata, sayan.bayan@gmail.com (19^th September, 2020 08:30 IST)

Dielectica traverses through the literature on this device – and summarizes as they appear.

Correspondence prepared by: Sayan Bayan, S. N. Bose National Centre for Basic Sciences, Kolkata, sayan.bayan@gmail.com (14^th September, 2020 08:30 IST)

KOLKATA: In everyday life for most of the inhabitant purposes, handwriting based signatures are used to authenticate individuals to maintain security as well as privacy. However, the forgery signature based scams have emerged as a common ground behind many of the big losses in monetary transactions or other security matters in daily life applications. Thus, signature authentication via handwriting recognition is a key challenge and must be addressed by the scientific community seriously.

In this context, the research group of Prof. Zhong Lin Wang from the Georgia Institute of Technology, USA, has come up with a signature identification platform that has promising ability in security defense, and private information protection applications. According to the report recently published in the scientific journal ‘Nano Energy’, Prof. Wang and coworkers have demonstrated the handwriting recognition ability of a device called ‘triboelectric nanogenerator’ that runs without any external power supply.¹ Prof. Wang is regarded as the inventor of triboelectric nanogenerator which works in the coupled principle of contact electrification and electrostatic induction.² In such nanogenerator system, mechanical stimulus induces a current flow and can power up small electronic gadgets.

It is quite obvious that any kind of writing or drawing exerts mechanical pressure on the writing platform and such mechanical pressure can be used to generate electric power leading to a self-powered system. Further, the combination of signal processing and machine learning technologies with a triboelectric nanogenerator endows the ability to recognize the handwriting of different people. The research group has demonstrated that such self-powered writing pads can recognize writings of English words, Chinese characters as well as Arabic numerals with classification accuracies of 99.66%, 91.36% and 93.63%, respectively. It is expected such triboelectric nanogenerator based smart systems can play a vital role for protecting personal information in various segments of modern life in the near future.

Sources:
¹Nano Energy 77 (2020) 105174. DOI: 10.1016/j.nanoen.2020.105174
 ²Nano Energy 1 (2012) 328. DOI: 10.1016/j.nanoen.2012.01.004

Dielectica dives through India’s milestone events in space science – and summarizes as they appear

Correspondence prepared by: Ayan Dey (7th September, 2020 11:59 IST)

From a simple beginning in the early 1960s, India’s journey to the space has achieved several milestones. These include fabrications and launching of satellites, space vehicles, orbiter missions etc. This dream journey has started when Dr. Vikram Sarabhai, known to be the Father of Indian space programme formed an organization in 1962 named Indian National Committee for Space Research (INCOSPAR). In 1969 the INCOSPAR was renamed as Indian Space Research Organization (ISRO). The Indian Space Research Organizations has completed 50 years of its glorious journey, since its foundation on 15th August, 1969. Its journey started from ARYABHATTA, BALLON experiment, BHASKARA-I, APPLE (India’s first geostationary experimental communication satellite, 1977-83), INSAT-IA, INSAT-IB, PSLV to highly classified missions like Chandrayaan-1, 2 and Mangalyaan (India’s first deep space mission). Today, the annual budget of Indian Space Research Organization (ISRO) is more than 10 thousand crores ($1.45 billion). The people who made it happen with their extraordinary visions and sheer hard work were – Dr. Vikram Sarabhai, U.R. Rao (who had developed

18 satellites (including Bhaskara, APPLE, INSAT and many more)), Rakesh Sharma (the first Indian to venture into space), A.P.J. Abdul Kalam also known as ‘Missile Man of India’ and many others. The most interesting and biggest discovery among all expeditions conducted by ISRO was tracing water on the Moon. Chandrayaan’s Moon Mineralogy Mapper (M3) experiment (2008) has shown evidence of water on the Moon. An even bigger success was India’s first deep space mission to Mars: the “Mars orbiter mission (MOM)” (2014). With that, India became the first country to have ever succeeded in orbiting the Mars after the failures of the US, China and Russia. It was the first major breakthrough after the GSLV Fat Boy failure in 2010.
ISRO has announced its next 10 years plan, consisting of some new mega missions. The most notable one among these is: GAGANYAAN – India’s first ever manned mission, this project will make India the fourth nation in the world to achieve that benchmark. Approximate budget of this mission is INR 10,000 crore and it will be India’s biggest and boldest space mission till date. It is intended to send a maximum of 3 astronauts for a minimum of 7 days by the year of 2022.

This manned-mission spacecraft basically consists of service and crew module, which is collectively known as the orbital module. GSLV MK-III, the three-stage heavy lift launch vehicle will be used for the launch of GAGANYAAN, as it is capable of carrying a high payload capacity for different application fields. This spacecraft is designed to carry 4-ton class of satellites into the Geosynchronous Transfer Orbit (GTO) and about 10 tons to Low Earth Orbit (LEO). Its powerful cryogenic stages help it in placing heavy payloads into the Low Earth Orbit’s 600 km altitude. Due to the huge amount of payloads, it uses two very strong rocket boosters (S200), to produce huge amount of thrust to lift the Spacecraft. Some key points about the GAGAANYAAN are –

• It consists of two models i.e. crew and service. The crew model, where the three astronauts will be staying, will have a mean diameter of 3.7 m and height 7 m.
• It will take maximum of 15-16 mins for earth’s parking orbit insertion.
• It will be placed 300-400 km off the low earth orbit (LEO).
• The spacesuits for this mission are being developed at the Vikram Sarabhai Space Centre, Bengaluru, India which will be orange in colour.
• The astronaut can breathe by these space suits for an hour, with the capacity of holding one oxygen cylinder.
• The astronaut will be able to see the sunrise and sunset and also able to do some experiment about the microgravity with the help of the crew capsule module. This capsule will rotate around the earth for every 90 minutes.
• After the accomplishment of whole mission, the capsule will land at the coast of Gujarat (maximum 36 hours to land).
• French Space Agency CNES will assist ISRO in providing expert advice in various fields viz. space medicine, health monitoring of the astronauts etc.

Apart from this, ISRO has planned other classified missions for the near future –
ADITYA-L1: This is basically will going to be ISRO’s first planned mission to study the Sun’s corona and its atmosphere.
MANGALYAAN-2: India’s second mission again to the MARS as an Orbiter-2 (2022 – 23)
CHANDRAYAAN-3: This will be going to the India’s third lunar mission (late 2020s).

VENUS MISSION: It is basically a Venusian mission to study its surface and atmosphere which is Earth’s closest siblings due to their similarities in their sizes (2023 – 25). The proposed satellites for this mission will weight about 175 kg of payloads and 500 watts of power.
Another one, probably the most interesting yet challenging one as we may call it: a dream to have India’s own international space station. This will wind up by 2028. The proposed station will be about 15-20 tonnes hosting people for more than 15 days. As India is moving with the ‘Make in India’ dream, these missions are not very far off from reality. Right from the first launch from an old church at Kerala, India’s journey to space has been quite remarkable throughout the last 50 years and an a member of the Elite Space Club it will also set a milestone for all other developed countries across the globe who are yet to succeed in space.

Reference : INDIA IN SPACE : Harper Collins Publishers India 2020 JJ Imprints Pvt Ltd, Noida, P-ISBN- 978-935-357-641-7