China
Africa
Explore chapters and articles related to this topic
Overview on Metal Oxide Perovskite Solar Cells
Published in Vijay B. Pawade, Paresh H. Salame, Bharat A. Bhanvase, Multifunctional Nanostructured Metal Oxides for Energy Harvesting and Storage Devices, 2020
N. Thejo Kalyani, S. J. Dhoble
Nanocrystal solar cells are a type of solar cell with nanocrystals coating the substrate. They employ nanocrystals, which are crystalline particles with at least one dimension measuring less than 1000 nm (quantum dot, quantum wire, quantum well). Nanocrystalline silicon is totally different from bulk-silicon in some properties, such as (1) carrier relaxation time (the time taken by the carriers to return back lower energy state) is dramatically reduced because of the established fact that they have large band gap, due to which electrons cannot quickly relax to its initial state because of a weak Coulomb interaction [18]. Hence, these electrons can contribute to the current; (2) formation of more than one electron per absorbed photon, generally known as multiple exciton generation (MEG) is possible. Silicon nanocrystal solar cells are relatively easy to make and hence cheap. By employing nanocrystals in solar cells, their efficiency can be enhanced to a certain extent.
Third-Generation Solar Cells
Published in Denise Wilson, Wearable Solar Cell Systems, 2019
Also, because of the discrete energy levels that are characteristic of QDs, it becomes possible for a single photon of light to generate more than one electron. This process, called multiple exciton generation (MEG) is a result of impact ionization by excited electrons. In most semiconductors, an electron excited into the conduction band by a photon of light relaxes to the bottom of the conduction band in processes that release heat. In a QD, however, the excited electron can collide with other electrons, imparting energy to those electrons that is sufficient for those electrons to be collected as current. This multiplicative effect caused by impact ionization and the resulting production of multiple excitons for a single photon makes it possible for QD PV cells to exceed the SQL of 33.7% efficiency (Shockley and Queisser 1961). Challenges in developing processes for the synthesis and production of QD films that reduce traps, defects, and other places where electrons can get lost before collection have held QDs back from surpassing the SQL. In 2019, the best research cell efficiency for a quantum dot (QD) was recorded at 16.6% (NREL 2019).
Material challenges for solar cells in the twenty-first century: directions in emerging technologies
Published in Science and Technology of Advanced Materials, 2018
Samy Almosni, Amaury Delamarre, Zacharie Jehl, Daniel Suchet, Ludmila Cojocaru, Maxime Giteau, Benoit Behaghel, Anatole Julian, Camille Ibrahim, Léa Tatry, Haibin Wang, Takaya Kubo, Satoshi Uchida, Hiroshi Segawa, Naoya Miyashita, Ryo Tamaki, Yasushi Shoji, Katsuhisa Yoshida, Nazmul Ahsan, Kentaro Watanabe, Tomoyuki Inoue, Masakazu Sugiyama, Yoshiaki Nakano, Tomofumi Hamamura, Thierry Toupance, Céline Olivier, Sylvain Chambon, Laurence Vignau, Camille Geffroy, Eric Cloutet, Georges Hadziioannou, Nicolas Cavassilas, Pierre Rale, Andrea Cattoni, Stéphane Collin, François Gibelli, Myriam Paire, Laurent Lombez, Damien Aureau, Muriel Bouttemy, Arnaud Etcheberry, Yoshitaka Okada, Jean-François Guillemoles
The main energy losses during the conversion of solar energy to electrical power by a solar cell are transmission losses and thermalization losses, with different relative contributions as a function of the semiconductor bandgap (see Figure 3 below). Several strategies exist to reduce those losses, such as multijunction cells, hot-carrier solar cells, intermediate band solar cells, or multiple exciton generation.
Strategy trends of core/multiple shell for quantum dot-based heterojunction thin film solar cells
Published in Australian Journal of Electrical and Electronics Engineering, 2022
Ahmed Thabet Mohamed, S. Abdelhady
Quantum dots in case of bulk semiconductors can generate multiple exciton (electron–hole pairs) after collision with one photon of energy exceeding the band gap. Therefore, absorption of a single photon generates multiple electron–hole pairs. These phenomena are called multiple exciton generation MEG (Ebrahim 2015). There are three types considered as a development on previous depleted heterojunction solar cells (Quantum funnels (QF), quantum junction (QJ), and heterojunction (HJ) QD solar cells), These three types were discovered most recently. Their configurations are considered as a development on previous depleted heterojunction solar cells. They aim to enhance the connection between quantum dots and wide bandgap semiconductors. A heterojunction quantum dots solar cell (HJ-QDSC) is the same as quantum junction solar cell except the p-n type QDs are made of different semiconductor materials. With traditional measurements of photovoltaics cells, the highest efficiency for a PbS: CdS combination in HJ-QDSC was 3.5% (Gonfa et al. 2014). Several n-type materials such as CdS and Bi2S3 have been combined to PbS QDs in a core shell structure like two planar layers on top of each other (Tang et al. 2012; Gonfa et al. 2014; Chang et al. 2013) or as bulk (Bhandari et al. 2013). Core shell nanostructures has ability for improving optical properties of photovoltaic cells. Especially, the metal-semiconductor core–shell nanoparticles are the focus of intensive research due to their enhanced electronic and optical properties. It is trusted that matching the surface plasmon resonance excitation energy from metal nanoparticles to the band gap energy of the semiconductor core that leads to fast energy transfer between semiconductor coating and metal cores (Chaokang et al. 2008; Ma et al. 2004; Sharma and Gupta 2007). Metal-semiconductor hetero-structures have tunable optical properties since the surface plasmon resonances properties are strongly dependent on the composition, dimension and morphology of metal nanoparticles (NPs) (Liu et al. 2013; Zhou et al. 2009).