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Our life is based on production and utilization of energy. We burn down a fossil fuel to heat and light up our homes, prepare food, and for quick travels. However, the fossil fuel resources are limited and energy production technologies affect our global climate and the ecological state of our environment. The most promising energy source which ena...
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... second method we have in mind to increase efficiency is by using hot electrons, generated charged carriers with energy that is higher than the semiconductor bandgap. All our previous derivations were based on assumption that each photon excites only one electron- hole pair and the exceeding energy dissipates as heat due to thermalization process. This was assumed on the fact that a photon can’t split to two or more particles. However, a “hot” particle may transfer the exceeding energy to other free particle by impact and thus to create another electron-hole pairs. Such chair reaction ionization impact exists in all semiconductors with very low efficiency. However, this efficiency may be increased using low dimensional structures such as quantum wells [12], quantum dots [13], or nano-crystals of above 5 nm size [10]. Detailed analysis of low dimensional structures that are applicable for the solar light converting was done by Martin Green [14]. It is necessary to take into account that the complication of the semiconductor structure also leads to the SRH (Shockley Reed Hall) recombination increasing. The third method to improve efficiency is based on utilizing various semiconductor materials in order to enlarge the spectral efficiency. Multi-junction devices, or hetero-junction devices, can reach larger spectral efficiency by capturing different parts of the solar spectrum. The main principle of hetero-junction devices organization is shown in figure 11 [15]. A multijunction device is a stack of individual single-junction cells in descending order of bandgaps. The top cell captures the high-energy photons and passes the rest of the photons on to be absorbed by lower-bandgap cells. Sze has shown [4] that consecutive combination of 36 junctions may attain an ideal efficiency of ...
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... The recombination losses are defined by various processes in the semiconductor: radiative recombination (luminescence), Auger recombination, recombination on the semiconductor defects and impurities (Shockley-Read-Hall or SRH recombination), and surface recombination, see e.g. [6, 7]. Technological losses are made up of various inaccuracies and incompatibilities at each stage of the technological process. ...
Solar cells made of single-crystalline silicon, as alternative energy sources, became the most widely used solar cells in recent years. The mainstream manufacturing approach is to process the cells and assemble these into photovoltaic (PV) modules. However, the direct conversion of solar energy into electricity using the PV effect suffers from low efficiency. Thus, increasing the conversion efficiency at low production costs becomes the main goal of solar cell manufacturers. One way to increase the efficiency of a solar cell is to use an ultra-wide layer of intrinsic semiconductor as the depletion region of a PN junction. In our work, we present a novel geometrical concept of PIN structure for PV applications. The width of the intrinsic layer in our construction is 5-20 mm. Moreover, in our novel structure, the light irradiation acts directly on the active region of the PV cell, which enables bi-facial irradiation and results in ∼28 % conversion efficiency. A low cost fabrication is ensured in our design due to a new manufacturing technology by eliminating some expensive processes, such as photolithography. The feasibility proof of the novel concept in mono-crystalline silicon solar cells is presented. We demonstrate simulation results and preliminary experimental results confirming our approach.
