SIRACUSA · Study on intermediate band materials with prevailing radiative carrier recombination for superior solar energy applications
7РП — „Хора“ (Действия „Мария Кюри“)
- Период
- 2012-10-01 → 2014-09-30
- Финансиране от ЕС
- 200 372 €
- Участници
- 1
- Схема
- MC-IEF
Линиите свързват координатора с партньорите.
Накратко на български
Слънчевите клетки с междинна лента се изследват чрез добавяне на примеси от желязо, хром и кобалт в полупроводника GaAs. Това помага за повишаване на ефективността при концентрирана слънчева светлина, като преодолява ограниченията на сегашните многослойни устройства.
Кратко обяснение, генерирано от езиков модел по текста на CORDIS. Оригиналът е по-долу.
Резултати накратко
Study on intermediate band materials with prevailing radiative carrier recombination for superior solar energy applications
Solar cells (SCs) fall into two general types, large area low cost devices for one sun applications and small area high efficiency devices for concentrator applications. For the latter application, efficiency is a key factor. At present the highest efficiency SCs are triple junction devices with an efficiency ~44% under concentration. However, in such SCs the current in each junction must be matched and if the distribution of solar energy changes e.g. due to clouds obscuring the direct sunlight, the overall efficiency drops and the current is determined by the least efficient of the three junctions. Several proposed third generation SCs seek to overcome this restriction [1], including the intermediate band solar cell (IBSC) concept [2]. The overall objective of this project was to develop an advanced, third generation, solar cell for concentrator applications based on the intermediate band concept [2]. Various approaches to this have been based on insertion of quantum dots (QD) in the intrinsic region of a p-i-n semiconductor, but the absorption of radiation using this method is limited due to the finite number of QDs. Instead our approach is by the insertion of an intermediate band based on deep level impurities [2]. In order to achieve this overall goal, we have grown by molecular beam epitaxy (MBE) GaAs structures containing very large concentrations of deep levels, including Fe, Cr & Co. According to the theory [2], at a sufficiently high concentration the wavefunctions should overlap to form a band within the intrinsic region of the GaAs and thus suppress the non-radiative processes normally associated with mid-gap deep levels. Due to the finite solubility of such impurities at conventional MBE growth temperatures, it is essential to grow the samples at very low temperature, which in turn can introduce deleterious point defects. By carefully adjusting the growth conditions, to minimise the concentration of point defects, we have achieved this objective. We have produced GaAs samples containing ~2 % Fe co-doped with Si, which are both electrically and optically active. SIMS studies show we have successfully incorporated Fe at the expected level (Milestone 1). The electrical properties have been studied by Hall effect measurements. The measurements show that both the conductivity and mobility are influenced by exposure to light. This result shows that we have good evidence for the formation of the intermediate band in GaAs (Milestone 2). Using this knowledge we have also grown and processed complete intermediate band SCs, which are currently being characterised at UPM Madrid (Milestone 4). This work will now be submitted for publication (Milestone 3). References 1) G Conibeer, Materials Today, 10 (2007) 42 2) A Luque and A Marti, Phys. Rev. Lett., 78 (1997) 5014
Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз
Цел на проекта
This project proposes an experimental investigation on the basic material physics and the feasibility of the intermediate band solar cell (IBSC), which is a new type of photovoltaic device with the potential for very high conversion efficiencies and low spectral sensibility. The operation of the IBSC relies on the use of a light absorbing material that differs from a conventional semiconductor by having an intermediate band (IB) of allowed electron states within the band gap. According to the theoretical model, a p-IB material-n solar cell can render a higher photocurrent than a comparable p-n structure, without significant degradation of the voltage. The work to be performed in this project comprises the production (epitaxial growth) of IB material samples and devices, and their characterization. The approach proposed is to focus on a well-known material as semiconductor host (GaAs). The IB materials will be synthesized by introducing high densities of a transition metal impurity, such as Fe or Co, in that host. The characterization tools will include time-resolved photoluminescence, electrical transport measurements and optical absorption spectroscopy. The main results expected from the project are: (a) to assess the feasibility of a material with a sufficiently high impurity content so as to exhibit the predicted properties of an IB material, whilst maintaining a sufficient crystalline quality (with emphasis on the radiative/non-radiative recombination properties); (b) to characterize the IB electrical and optical properties correlating them to optimized growth conditions. To fulfil those objectives we rely on the wide experience of Prof. Foxon’s group at University of Nottingham on epitaxial growth of heavily-doped spintronic materials, as well as on the knowledge of the fellow on IB solar cells. This project addresses fundamental physics questions which are relevant to the photovoltaic industry and to the European future energy needs.""
Оригинален текст от CORDIS (на английски).
Участници
- THE UNIVERSITY OF NOTTINGHAM · NottinghamКоординаторОбединеното кралство
Връзки
Данни: CORDIS, © Европейски съюз