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Passivating contacts and tandem concepts: Approaches for the highest silicon-based solar cell efficiencies
摘要： The efficiency of photovoltaic energy conversion is a decisive factor for low-cost electricity from renewable energies. In recent years, the efficiency of crystalline silicon solar cells in mass production has increased annually by about 0.5–0.6%abs per year. In order to maintain this development speed, new technologies must be developed and transferred to industrial production. After the transition from full area Al back surface field cells to passivated emitter and rear contact cells, passivating contacts are an important step to get as close as possible to the efficiency limit of single junction Si solar cells. The theoretical background and the two prominent technologies for passivating contacts are presented and discussed. After implementing passivating contacts, the fundamental limit of single junction Si solar cells of 29.4% is in reach. Multi-junction solar cells are the most promising option to achieve efficiencies greater than 30%. Tandem technologies based on crystalline silicon as bottom cells have the advantage that they are based on a mature technology established on a gigawatt scale and can partially use the existing production capacity. In addition, silicon has an ideal bandgap for the lower subcell of a tandem solar cell. The two most promising material candidates for the top cell, i.e., III/V and perovskites, will be discussed. The presented technology routes show that silicon is able to maintain its outstanding position in photovoltaics in the coming years.
关键词： perovskites,multi-junction solar cells,III/V,photovoltaic energy conversion,passivating contacts,tandem technologies,crystalline silicon solar cells
更新于2025-09-23 15:19:57
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Diluted nitride type-II superlattices: Overcoming the difficulties of bulk GaAsSbN in solar cells
摘要： We demonstrate type-II GaAsSb/GaAsN superlattices (SL) as a suitable structure to form the lattice-matched 1.0–1.15 eV subcell that would allow the implementation of the optimum monolithic multi-junction solar cell design. The separation of Sb and N atoms during growth leads to an improved composition homogeneity and a lower defect density than in the bulk GaAsSbN counterparts. The type-II band alignment SLs provide long radiative lifetimes that facilitate carrier collection as compared to equivalent type-I SLs. Moreover, the radiative lifetime can be controllably tuned through the period thickness, which is not possible in type-I SLs. A reduced period thickness results in enhanced absorption due to increased wavefunction overlap, as well as in a change in the transport regime from diffusive to quasiballistic, providing improved carrier extraction efficiency. As a result, the short period SL single-junction solar cells show an enhanced power conversion efficiency of 134% over the equivalent bulk devices.
关键词： Strain-balanced,GaAsSbN,Type-II band Alignment,Multi-junction solar cells,Superlattices,1 eV bandgap
更新于2025-09-23 15:19:57
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Design of Curved Fresnel Lens with High Performance Creating Competitive Price Concentrator Photovoltaic
摘要： In this paper, the design of a curved Fresnel lens applying to the concentrator photovoltaic system is proposed by using the edge ray theorem, the Snell’s law, and the conservation of optical path length. The new structure of the curved Fresnel lens can improve significantly the uniformity of sunlight distribution over the solar cell while the concentration ratio can reach a high value of 900 times. The good uniform distribution can be obtained by using the novel idea. The novel idea is based on the uniform sunlight distribution of every groove of the lens so that the whole lens also distributes uniformly the sunlight beam over the receiver. The structure of the lens is built by two surfaces: input surface (or upper surface) as a part of spherical surface and output surface (or lower surface) that consists all grooves of the lens. Matlab program is used to design the input and the output surfaces of the lens. The input surface and the output surface are independent to each other in construction in Matlab. LighttoolsTM software is used to optimize the structure of the novel lens. Furthermore, LighttoolsTM is also used to perform a simulation to examine the efficiency of the lens in concentrator photovoltaic (CPV) system by using the light source with a wide spectrum of 380 – 1600 nm. The results show that the lens has an acceptance angle of 0.80 and good optical efficiency (>85%).
关键词： concentrator photovoltaic (CPV),Fresnel lens,solar energy,high concentration ratio,multi-junction solar cells,uniform irradiance distribution,CPV without secondary optical element (SOE)
更新于2025-09-12 10:27:22