First all-carbon solar cell

Stanford University scientists have built the first solar cell made entirely of carbon, a promising alternative to the expensive materials used in photovoltaic devices today.
The results are published in the Oct. 31 online edition of the journal ACS Nano (” Evaluation of Solution-Processable Carbon-Based Electrodes for All-Carbon Solar Cells”).
“Carbon has the potential to deliver high performance at a low cost,” said study senior author Zhenan Bao, a professor of chemical engineering at Stanford. “To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon. This study builds on previous work done in our lab.”

Unlike rigid silicon solar panels that adorn many rooftops, Stanford’s thin film prototype is made of carbon materials that can be coated from solution. “Perhaps in the future we can look at alternative markets where flexible carbon solar cells are coated on the surface of buildings, on windows or on cars to generate electricity,” Bao said.
The coating technique also has the potential to reduce manufacturing costs, said Stanford graduate student Michael Vosgueritchian, co-lead author of the study with postdoctoral researcher Marc Ramuz.
“Processing silicon-based solar cells requires a lot of steps,” Vosgueritchian explained. “But our entire device can be built using simple coating methods that don’t require expensive tools and machines.”
Carbon nanomaterials
The Bao group’s experimental solar cell consists of a photoactive layer, which absorbs sunlight, sandwiched between two electrodes. In a typical thin film solar cell, the electrodes are made of conductive metals and indium tin oxide (ITO). “Materials like indium are scarce and becoming more expensive as the demand for solar cells, touchscreen panels and other electronic devices grows,” Bao said. “Carbon, on the other hand, is low cost and Earth-abundant.”
For the study, Bao and her colleagues replaced the silver and ITO used in conventional electrodes with graphene – sheets of carbon that are one atom thick –and single-walled carbon nanotubes that are 10,000 times narrower than a human hair. “Carbon nanotubes have extraordinary electrical conductivity and light-absorption properties,” Bao said.
For the active layer, the scientists used material made of carbon nanotubes and “buckyballs” – soccer ball-shaped carbon molecules just one nanometer in diameter. The research team recently filed a patent for the entire device.
“Every component in our solar cell, from top to bottom, is made of carbon materials,” Vosgueritchian said. “Other groups have reported making all-carbon solar cells, but they were referring to just the active layer in the middle, not the electrodes.”
One drawback of the all-carbon prototype is that it primarily absorbs near-infrared wavelengths of light, contributing to a laboratory efficiency of less than 1 percent – much lower than commercially available solar cells. “We clearly have a long way to go on efficiency,” Bao said. “But with better materials and better processing techniques, we expect that the efficiency will go up quite dramatically.”
Improving efficiency
The Stanford team is looking at a variety of ways to improve efficiency. “Roughness can short-circuit the device and make it hard to collect the current,” Bao said. “We have to figure out how to make each layer very smooth by stacking the nanomaterials really well.”
The researchers are also experimenting with carbon nanomaterials that can absorb more light in a broader range of wavelengths, including the visible spectrum.
“Materials made of carbon are very robust,” Bao said. “They remain stable in air temperatures of nearly 1,100 degrees Fahrenheit.”
The ability of carbon solar cells to out-perform conventional devices under extreme conditions could overcome the need for greater efficiency, according to Vosgueritchian. “We believe that all-carbon solar cells could be used in extreme environments, such as at high temperatures or at high physical stress,” he said. “But obviously we want the highest efficiency possible and are working on ways to improve our device.”
“Photovoltaics will definitely be a very important source of power that we will tap into in the future,” Bao said. “We have a lot of available sunlight. We’ve got to figure out some way to use this natural resource that is given to us.”

Source: Nanowerk News


Invasion of wild climber (Mikinia Micrantha) poses threat to rhino habitat

Invasion of a wild climber, which is also called Mikinia Micrantha, is posing a serious threat to the rhino habitat in Chitawan National Park (CNP) , Save the Environment Foundation (SEF) said.

In a press conference organised in Kathmandu Sunday, SEF founder Chanda Rana said the recent survey carried out by the Zoological Society of London found that 50 percent of the rhino have already been affected by the Mikania.

“During my filming I found one third of prime rhino habitat in the CNP were already engulfed by the infestation of the wild weed,” said Rana who has recently produced a documentary called ‘Mile a Minute, a serious threat to CNP’, as an initiation to raise awareness regarding the impact of the wild climber.

Rana also informed that SEF will organise a national workshop in the second week of November at CNP which will have the participation of all the stakeholders on Mikinia infestation.

The SEF has also planned to arrange visit of Prime Minister Baburam Bhattarai to some areas of the national park where infestation of Mikinia Micrantha is most severe.

What is Mikania micrantha ?

Mikania micrantha is a perennial creeping climber known for its vigorous and rampant growth. It is branchy, slender-stemmed perennial vine. The leaves are arranged in opposite pairs along the stems and are heart-shaped or triangular with an acute tip and a broad base. Leaves may be 4-13cm long. The flowers, each 3-5mm long, are arranged in dense terminal or axillary corymbs. Individual florets are white to greenish-white. The seed is black, linear-oblong, five-angled and about 2mm long. Each seed has a terminal pappus of white bristles that facilitates dispersal by wind or on the hair of animals.

Botanical name: Mikania micrantha (L.) Kunth
Nepali: Lahare Banmara
Common names: American rope (English), Chinese creeper (English)

Mikania micrantha is plant killing weeds and which is mostly affects young regeneration and creates unfavorable condition for regeneration. It is newly seen in Nepal and it is not in people’s notice. Several countries and territories are trying to manage the major weeds of the region but result seen is not effective. It can be reduced or eradicated through creating shade which is not suitable for Mikania micrantha. Several community forests are also affected by this weeds which can be eradicated through user participation. It is important to control or destroy in very beginning before dispersal of seeds. If it is spread widely will reduce the productivity, destroy regeneration and degrade the forest condition. Once it proliferated throughout the forest then will become costly to control by any means. Control burning is also one way to contain chances of wider spreading. more

Very clear sign of global warming in the Everest region

In this video produced by, Mountaineer David Breashears compares the panoramic photo he took in 2008 of Mount Everest and its surrounding glaciers with one taken in 1921, and explains the enormous scale and rapid speed of the ice loss at the world’s “tallest water tower.” See the evidence with your own eyes.

In Khumjung village high up in the Nepal Himalayas, villagers are struggling to find fresh supplies of water now that glaciers have melted. This short video highlights these problems and the dilemmas that these communities face.

Global Tiger Workshop Kicks off; PM anounces strategies to preserve tiger

Kathmandu Global Tiger Workshop 2009, a first of its kind event organised to chart out strategies to preserve Tiger, has kicked off, Tuesday.

(from left) Vice Minister for Natural Resources and Environment of Thailand Pimuk Simaroj, Prime Minister Madhav Kumar Nepal and Minister for Forest and Soil Conservation Deepak Bohara at the inaugural ceremony of the Global Tiger Workshop in Kathmandu, Tuesday, Oct 27 09.
Prime Minister Madhav Kumar Nepal inaugurated the four-day workshop amid a function in Kathmandu, this morning.

Some 250 scientists, tiger experts, policy makers, conservationists and government officials from 20 countries, including India, Bangladesh, Bhutan, Nepal, Thailand, China, are participating in the workshop.

Addressing the workshop, PM Nepal expressed Nepal’s commitment towards the preservation of tigers and announced some key strategies Nepal will adopt for the same.

“I would like to reiterate that the Government of Nepal is firmly committed to the cause of conservation of this unique species and its habitat,” PM Nepal said. “We are now in the process of having high level mechanisms for National Tiger Conservation Authority and Wildlife Crime Control Coordination Committee.”

PM Nepal also sought international cooperation to curb trans-border poaching of tiger parts.

Nepal has set an ambitious target of increasing the tiger population to 250 by the next ten years. At present there are 120 adult tigers in Nepal.

In the world, the tiger population in the wild is 3,500. It was about 7,000 in 2000. Besides, tiger is also reared in controlled situation in countries like China, Vietnam and Thailand. Whether tigers should be reared in controlled situation or not will also be discussed in the workshop.

Nepal government is also planning to double the size of Bardiya National Park, one of the chief tiger habitats, by annexing some 900 sq. km of forest area in a bid to preserve tiger along with other wild animals.

The workshop will conclude Friday issuing a Kathmandu declaration which includes various strategies and policies to increase the tiger population.

Bardiya National Park to be doubled in size

The government is preparing to expand the area of Bardiya National Park (BNP) to double its present size by annexing 898 sq. km of forest area along the east-west highway in Dang, Nagarik Daily reported.

The area of the National Park at present is 968 sq. km.


Prime Minister Madhav Kumar Nepal will officially announce the expansion of BNP at the inaugural function of Global Tiger Workshop, slated to start from Tuesday in Kathmandu.

The expansion of the National Park is vital for the conservation of Tigers as the area proposed to be annexed is considered an important area for habitat and food for tigers, according to wildlife experts. BNP is home to many important wildlife inlcuding the rare one-horned Rhino, Tigers and elephants.

Erstwhile Prime Minister Girija Prasad Koirala had unveiled plans to expand BNP as a ‘gift to the earth’ in 2000. However, the plan had not materialised due to armed conflict in the country.

Of the area to be annexed 549 sq. km will be forest area, while 345 sq. km will be buffer zone. Some 50 additional staff including army personnel for security will be required for the upkeeping of the additional area. It will also include 13 VDCs of Dang district.

The santuary was established in 1976 with the name ‘Karnali Wildlife Conservation’. It was renamed as ‘Bardiya Wildlife Conservation’ in 1982 and converted to a National Park in 1998.

Some 1600 families were displaced from an important Rhino habitat Babai valley while expanding the the National Park.