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Two-Dimensional Heterojunction Photovoltaic Cells with Low Spontaneous-Radiation Loss and High Efficiency Limit
摘要： This work presents theoretical investigations on the spontaneous-radiation loss of two-dimensional van der Waals heterojunction photovoltaic cells (2D-PVcs) combined with an interference-based light-trapping structure. We find that 2D-PVcs possess much lower spontaneous radiation loss, since the solid angle of the spontaneous radiation is a magnitude smaller than that in traditional PVcs. The efficiency limit of a 2D-PVc can be 10% larger than that of a traditional PVc. Furthermore, we demonstrate that the spontaneous-radiation loss can be further reduced by introducing only a weak light-concentrating system, approaching the efficiency limit of traditional PVcs under perfect focus. In a trapped structure, the smaller the light absorption coefficients of the photovoltaic cells, the higher are the efficiency limits that are achieved. Finally, the spontaneous-radiation loss increases as the battery thickness increases, indicating that the 2D-PVc has the lowest spontaneous emission loss because of its extremely low thickness.
关键词： photovoltaic cells,two-dimensional heterojunction,spontaneous-radiation loss,light-trapping structure,efficiency limit
更新于2025-09-11 14:15:04
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Performance improvement of thin-film silicon solar cells using transversal and longitudinal titanium nitride plasmonic nanogratings
摘要： Taking advantage of plasmonic nanostructures for light trapping in thin-film silicon solar cells has attracted ample attention among researchers. Titanium nitride (TiN) has recently been introduced as a promising material exhibiting plasmonic properties similar to gold while taking advantage of low cost, low loss, and CMOS compatibility. Moreover, utilization of TiN offers a good tunability since the optical properties of TiN depend on many fabrication parameters. In this work, transversal and longitudinal TiN nanograting arrays have been employed to act like perpendicular polarizers trapping the incident light in the active layer of the cell. Using optical and electrical simulations, it has been shown that the design provides a significant enhancement in the performance of thin-film silicon solar cells owing to the excitation of surface plasmon resonances and their resultant light trapping. Thanks to the employment of TiN nanogratings, the device offers a broadband absorption enhancement with a considerable improvement at the near infrared wavelengths in which the absorption of bare silicon layer is weak. The proposed thin-film cell results in short-circuit current and power conversion efficiency of about 26.46 mA/cm2 and 12.27%, respectively proving the proficiency of the design for performance improvement of thin-film photovoltaic systems.
关键词： Titanium nitride (TiN),Light trapping,Thin-film silicon solar cells,Plasmonic nanostructures
更新于2025-09-11 14:15:04
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Boosting the ultra-stable unencapsulated perovskite solar cells by using montmorillonite/CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> nanocomposite as photoactive layer
摘要： Lead halide perovskites, such as methylammonium lead iodide (MAPbI3) can reach near 100% internal quantum e?ciency in single solar cells, but they still encounter significant thermodynamic losses in photon energy to o?set device photovoltage and performance. Herein, a novel prismatic perovskite solar cell with light trapping configuration, namely, Prim PVSC, is designed to mitigate such losses in devices, through modulating the pathway of light inside series cells, wherein incident high-to-low energy photons are separately captured by four horizontally aligned MAPbIxBr3?x subcells with varied bandgaps. This newly designed PVSC has remarkably led to a record open circuit voltage of 5.3 V in four series devices and power conversion e?ciency of 21.3%, which could provide a new way to break the performance bottleneck of perovskites. Practically, this type of device architecture could also be applied in flexible modules for large-area application.
关键词： perovskite solar cells,light trapping,photovoltage,thermodynamic losses,power conversion efficiency
更新于2025-09-11 14:15:04
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The importance of accurate determination of optical constants for the design of nanometallic light-trapping structures
摘要： The optical constants of many metals commonly used in solar cells, e.g. as contacts, rear side planar reflectors, or more complex nanopatterned light-trapping structures, can vary depending on deposition method, thickness and other factors, and as such are not documented consistently in the literature. In the case of nanometallic light-trapping structures specifically designed to improve absorption in a solar cell, the choice of optical constants used in simulations significantly affects the predicted enhancement, as well as the structure's optimal dimensions. The trade-off between coupling into guided modes in the photovoltaic material and the number of photons absorbed parasitically in the metal leads to small differences in the optical constants giving significantly different results for the quantum efficiency and photogenerated current. This work documents several optical constant sources for silver, aluminium, gold and titanium, and the effect this has on plasmon quality factors. The effect of choosing different optical constant sources on modelling outcomes is quantified by considering the optimization of a test structure comprising a grid of metal nanodisks on the front surface of a thinned-down GaAs cell. Finally, we define a new spectrally-integrated figure of merit for comparing the expected performance of metals in light-trapping structures based on their optical constants, which we name the spectral absorption enhancement factor (SAEF).
关键词： RCWA,Light-trapping,Metallic gratings,Surface plasmons,Ultra-thin solar cells
更新于2025-09-10 09:29:36
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Nanowires for energy: A review
摘要： Semiconductor nanowires (NWs) represent a new class of materials and a shift from conventional two-dimensional bulk thin films to three-dimensional devices. Unlike thin film technology, lattice mismatch strain in NWs can be relaxed elastically at the NW free surface without dislocations. This capability can be used to grow unique heterostructures and to grow III-V NWs directly on inexpensive substrates, such as Si, rather than lattice-matched but more expensive III-V substrates. This capability, along with other unique properties (quantum confinement and light trapping), makes NWs of great interest for next generation optoelectronic devices with improved performance, new functionalities, and reduced cost. One of the many applications of NWs includes energy conversion. This review will outline applications of NWs in photovoltaics, thermoelectrics, and betavoltaics (direct conversion of solar, thermal, and nuclear energy, respectively, into electrical energy) with an emphasis on III-V materials. By transitioning away from bulk semiconductor thin films or wafers, high efficiency photovoltaic cells comprised of III-V NWs grown on Si would improve performance and take advantage of cheaper materials, larger wafer sizes, and improved economies of scale associated with the mature Si industry. The thermoelectric effect enables a conversion of heat into electrical power via the Seebeck effect. NWs present an opportunity to increase the figure of merit (ZT) of thermoelectric devices by decreasing the thermal conductivity (j) due to surface phonon backscattering from the NW surface boundaries. Quantum confinement in sufficiently thin NWs can also increase the Seebeck coefficient by modification of the electronic density of states. Prospects for III-V NWs in thermoelectric devices, including solar thermoelectric generators, are discussed. Finally, betavoltaics refers to the direct generation of electrical power in a semiconductor from a radioactive source. This betavoltaic process is similar to photovoltaics in which photon energy is converted to electrical energy. In betavoltaics, however, energetic electrons (beta particles) are used instead of photons to create electron-hole pairs in the semiconductor by impact ionization. NWs offer the opportunity for improved beta capture efficiency by almost completely surrounding the radioisotope with semiconductor material. Improving the efficiency is important in betavoltaic design because of the high cost of materials and manufacturing, regulatory restrictions on the amount of radioactive material used, and the enabling of new applications with higher power requirements.
关键词： photovoltaics,light trapping,nanowires,quantum confinement,thermoelectrics,lattice mismatch,betavoltaics,III-V materials,semiconductor,energy conversion
更新于2025-09-09 09:28:46