Aug 27, 2020

New research illuminates future of tandem solar cells

nextgen nano
Solar Energy
Duncan Clark
3 min
Researchers demonstrate highly replicable efficiency increase in tandem organic photovoltaic devices
Researchers demonstrate highly replicable efficiency increase in tandem organic photovoltaic devices...

A team of researchers from nanotechnology specialist Nextgen Nano may have found a new way of accelerating the development of high efficiency organic photovoltaic (OPV) technology. Nextgen Nano’s latest research demonstrated that a relatively simple material, HSolar, was widely compatible as an interconnecting layer (ICL) with multiple solar cell materials in tandem solar cells. The material also showed stable performance and high efficiency, which were replicated by several different research groups.

The findings are described in the paper High-performance tandem organic solar cells using HSolar as the interconnecting layer, published in the Advanced Energy Materials journal and featured on the inside cover.

With this research, it is possible for future research groups to fabricate and develop increasingly efficient multi-junction (MJ) OPVs based on the Nextgen Nano team’s recipe. Results of simulations conducted by the team showed that an efficiency greater than 22 per cent could be achieved in the near future based on these findings.

“If we are to truly realise a brighter, more sustainable future, we need to accelerate widespread use of OPV technology,” explained Duncan Clark, director of operations at Nextgen Nano. “Unfortunately, organic solar technology has faced several challenges with the likes of efficiency and replication, which has hindered commercialisation.

“The team at Nextgen Nano has taken a crucial step in addressing these problems by not only demonstrating impressive efficiency in OPVs, but by doing so in a way that is proven to be replicable outside of the core research team.”

The research team was led by Nextgen Nano’s chief technology officer Dr Franky So and research scientist Dr Carr Ho. The researchers first set out to identify means of improving the efficiency of OPVs, which have traditionally been limited by the typically narrow absorption bands of organic semiconductor materials. Many solar cell researchers have tackled this issue in recent years by layering two complementary solar subcells to create MJ, or tandem, OPV devices that can achieve higher efficiencies.

The ICL provides a physical and electrical contact between subcells, and is essential to minimize the energy losses. The efficacy of the ICL is integral to the efficiency and functioning of MJ solar devices. The challenge so far has been selecting and developing an ICL that does not interfere with the layers underneath, allows efficient charge recombination without a loss in open-circuit voltage and produces replicable results.

In its study, Nextgen Nano’s PolyPower research team demonstrated an ICL formed of a new version of PEDOT:PSS–HTL Solar (HSolar) and Zinc Oxide (ZnO) nanoparticles. This ICL can be produced relatively simply using commercially available raw materials. When tested with two common organic tandem solar cells, the device demonstrated a power conversion efficiency of 14.7 per cent. 

The team shared this ICL recipe with other research groups to validate the repeatability of the results, with the other teams achieving similar efficiencies of up to 16.1 per cent. Simulations run by the Nextgen Nano team showed that this could increase to 22 per cent if using state of the art organic photoactive materials as the tandem cells.

Nextgen Nano is focussed on leading research into the use of nanotechnology to pioneer new clean technologies. The company has been working on advancing the development of OPV technology for several years, to support the next generation of flexible, efficient solar panels.

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Jun 25, 2021

UK must stop blundering into high carbon choices warns CCC

Dominic Ellis
5 min
The UK must put an end to a year of climate contradictions and stop blundering on high carbon choices warns the Climate Change Committee

The UK Government must end a year of climate contradictions and stop blundering on high carbon choices, according to the Climate Change Committee as it released 200 policy recommendations in a progress to Parliament update.

While the rigour of the Climate Change Act helped bring COP26 to the UK, it is not enough for Ministers to point to the Glasgow summit and hope that this will carry the day with the public, the Committee warns. Leadership is required, detail on the steps the UK will take in the coming years, clarity on tax changes and public spending commitments, as well as active engagement with people and businesses across the country.

"It it is hard to discern any comprehensive strategy in the climate plans we have seen in the last 12 months. There are gaps and ambiguities. Climate resilience remains a second-order issue, if it is considered at all. We continue to blunder into high-carbon choices. Our Planning system and other fundamental structures have not been recast to meet our legal and international climate commitments," the update states. "Our message to Government is simple: act quickly – be bold and decisive."

The UK’s record to date is strong in parts, but it has fallen behind on adapting to the changing climate and not yet provided a coherent plan to reduce emissions in the critical decade ahead, according to the Committee.

  • Statutory framework for climate The UK has a strong climate framework under the Climate Change Act (2008), with legally-binding emissions targets, a process to integrate climate risks into policy, and a central role for independent evidence-based advice and monitoring. This model has inspired similarclimate legislation across the world.
  • Emissions targets The UK has adopted ambitious territorial emissions targets aligned to the Paris Agreement: the Sixth Carbon Budget requires an emissions reduction of 63% from 2019 to 2035, on the way to Net Zero by 2050. These are comprehensive targets covering all greenhouse gases and all sectors, including international aviation and shipping.
  • Emissions reduction The UK has a leading record in reducing its own emissions: down by 40% from 1990 to 2019, the largest reduction in the G20, while growing the economy (GDP increased by 78% from 1990 to 2019). The rate of reductions since 2012 (of around 20 MtCO2e annually) is comparable to that needed in the future.
  • Climate Risk and Adaptation The UK has undertaken three comprehensive assessments of the climate risks it faces, and the Government has published plans for adapting to those risks. There have been some actions in response, notably in tackling flooding and water scarcity, but overall progress in planning and delivering adaptation is not keeping up with increasing risk. The UK is less prepared for the changing climate now than it was when the previous risk assessment was published five years ago.
  • Climate finance The UK has been a strong contributor to international climate finance, having recently doubled its commitment to £11.6 billion in aggregate over 2021/22 to 2025/26. This spend is split between support for cutting emissions and support for adaptation, which is important given significant underfunding of adaptation globally. However, recent cuts to the UK’s overseas aid are undermining these commitments.

In a separate comment, it said the Prime Minister’s Ten-Point Plan was an important statement of ambition, but it has yet to be backed with firm policies. 

Baroness Brown, Chair of the Adaptation Committee said: “The UK is leading in diagnosis but lagging in policy and action. This cannot be put off further. We cannot deliver Net Zero without serious action on adaptation. We need action now, followed by a National Adaptation Programme that must be more ambitious; more comprehensive; and better focussed on implementation than its predecessors, to improve national resilience to climate change.”

Priority recommendations for 2021 include setting out capacity and usage requirements for Energy from Waste consistent with plans to improve recycling and waste prevention, and issue guidance to align local authority waste contracts and planning policy to these targets; develop (with DIT) the option of applying either border carbon tariffs or minimum standards to imports of selected embedded-emission-intense industrial and agricultural products and fuels; and implement a public engagement programme about national adaptation objectives, acceptable levels of risk, desired resilience standards, how to address inequalities, and responsibilities across society. 

Drax Group CEO Will Gardiner said the report is another reminder that if the UK is to meet its ambitious climate targets there is an urgent need to scale up bioenergy with carbon capture and storage (BECCS).

"As the world’s leading generator and supplier of sustainable bioenergy there is no better place to deliver BECCS at scale than at Drax in the UK. We are ready to invest in and deliver this world-leading green technology, which would support clean growth in the north of England, create tens of thousands of jobs and put the UK at the forefront of combatting climate change."

Drax Group is kickstarting the planning process to build a new underground pumped hydro storage power station – more than doubling the electricity generating capacity at its iconic Cruachan facility in Scotland. The 600MW power station will be located inside Ben Cruachan – Argyll’s highest mountain – and increase the site’s total capacity to 1.04GW (click here).

Lockdown measures led to a record decrease in UK emissions in 2020 of 13% from the previous year. The largest falls were in aviation (-60%), shipping (-24%) and surface transport (-18%). While some of this change could persist (e.g. business travellers accounted for 15-25% of UK air passengers before the pandemic), much is already rebounding with HGV and van travel back to pre-pandemic levels, while car use, which at one point was down by two-thirds, only 20% below pre-pandemic levels.

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