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The discussion of ultrathin crystalline silicon solar cell (UCSC) thickness and light enhancement patterns has long been a practical topic in its field with the objective of achieving optimum efficiency. In this work, we distinguish between the effects of the top and bottom structural designs on the light absorption of ultrathin crystalline-silicon solar cell. Nanopyramid (NP) front surface and distributed Bragg Reflector (DBR) bottom layer as enhancement agent was combined and its relation with thickness of solar cell was studied thoroughly. The relationship of photonic interaction between the top and bottom surfaces is also examined. Based on our simulation results, the optimized cell architecture consists of a 4 μ m-thick film combined with nanopyramid of 800 nm period and bottom reflector of 4 pair DBRs. The maximum achievable photo-current density of 36.72 mA/cm2 was obtained, which is among the best results of prior research for UCSC.

Structural design with high light absorption is the key challenge for thin film solar cells because of its poor absorption. In this paper, the light-trapping performance of silicon inclined nanohole arrays is systematically studied. The finite difference time domain method is used to calculate the optical absorption of different inclination angles in different periods and diameters. The results indicate that the inclined nanoholes with inclination angles between 5° and 45° demonstrate greater light-trapping ability than their counterparts of the vertical nanoholes, and they also show that by choosing the optimal parameters for the inclined nanoholes, a 31.2 mA/cm2 short circuit photocurrent density could be achieved, which is 10.25% higher than the best vertical nanohole system and 105.26% higher than bare silicon with a thickness of 2330 nm. The design principle proposed in this work gives a guideline for choosing reasonable parameters in the application of solar cells.

In this work, we reported a controllable preparation of nanoporous Ni3S2 films by a simple solvothermal-assisted sulfuration of nickel foam. The pore size can be easily adjusted by controlling the sulfuration time. Electrochemical tests show that the specific capacitance and the cycling performance of the Ni3S2 films were sensitive to their pore size. The Ni3S2 films with optimal pore size demonstrate a high specific capacitance (3.42 F/cm2 at 1 mA/cm2) and excellent cycling stability (about 102% after 4250 cycles at 7.5 mA/cm2). By contrast, the Ni3S2 films with either too large or too small pore size show much lower capacitance and relatively worse cycling stability. An asymmetric supercapacitor by using the optimal Ni3S2 film as the positive electrode and activated carbon coated on Ni foam as the negative electrode was also successfully assembled, which exhibited a superior energy density of 41.8 Wh/kg at power density of 155 W/kg and a high capacitance retention of 76.6% after 2000 cycles.

An InGaAs/AlGaAs quantum-well laser structure was grown on a silicon substrate by adopting a three-step grown thin (1.8 μm) and simple buffer layer. The whole structure was grown by metalorganic chemical vapor deposition. The material quality was characterized by transmission electron microscopy, photoluminescence spectra, and electrochemical capacitance–voltage profiler. It shows that the threading dislocation density and interface roughness are effectively reduced, and the active region's optical properties grown on a silicon substrate are comparable to that grown on a GaAs substrate. Broad stripe lasers have also been fabricated. The cavity length and stripe width are 1 mm and 15 μm, respectively. An extremely low-threshold current density of 313 A/cm 2 has been achieved under pulsed condition at room temperature. Meanwhile, the laser can operate under continuous wave condition at the temperature of 240 K. The above results make us more confident for realizing better performance of Si-based III–V semiconductor lasers by further improvement of the material growth method.

Because of the existence of “loads second time effect” in reinforceing damaged internal pressure steel pipeline without prestressed FRP, the fiber cannot fully play it’s advantage of high strength. Prestressed FRP is one of the effective ways to solve this problem. According to the BFRP reinforcement of damaged internal pressure steel pipeline, this paper designed a set of the circumferential prestress stretching and anchoring integral anchorage. And tested the conversion relation between torque and stress of BFRP sheet.

Ultrathin crystalline silicon solar cells are a promising technology roadmap to achieve more cost effectiveness. However, experimental reports on ultrathin crystalline silicon cells with thickness less than 20 µm are rare. Here, we experimentally fabricate and investigate ultrathin monocrystalline silicon solar cells consisting of 16 µm-silicon base thickness and low-cost front random pyramidal texture with the feature size of 1-2 µm. The normalized light absorption is calculated to explain the measured external quantum efficiency. The achieved efficiency is 15.1% for the single-layer passivated textured solar cell. In addition, via double-layer passivation of Al2O3/SiNx, the efficiency is further increased to 16.4% for the best textured cell, which significantly improves the absolute efficiency with Δη = 1.3%.

A design of ultrathin crystalline silicon solar cell with Si3N4 circular truncated cone holes (CTCs) arrays on the top is proposed. In this article, we perform an optical simulation of the structure. The finite-difference time-domain method is used to calculate the optical absorption of different periods, radius of top and bottom circles and depth of Si3N4 CTCs. The short-circuit current density generated by the optimized cells (30.17 mA/cm2) is 32.44% more than the value gained by control group (with flat Si3N4). Then adding a layer of back silver to allow us to better analyze optical absorption. Later, we simulate the optimization of the same configuration of different silicon thicknesses and find that our structure does enhance the light absorption. This work uses a combined path towards achieving higher photocurrent ultrathin crystalline silicon solar cells by constructing the texture of anti-reflection coating.

We report a structural design of ultrathin perovskite solar cells based on a conformal structure at the rear surface for potential applications in both single-junction and tandem cells. The light transmittances of the front and the rear surfaces are calculated in the wavelength range of 300–800 nm via the finite difference time domain numerical simulation method. Compared with the reference cell, significant photocurrent density enhancement of 27.5% and 29.7% are achieved when the ratios of height to width of the fluorine doped tin oxide nanoblock are 2 and 3, respectively. For the case with a hole transport material layer, the enhancements of photocurrent density enhancements are 19.2% and 29.0%, respectively. When back Au is removed, the photocurrent density also has notable enhancements of 23.3% and 45.9%, respectively. The achieved results are beneficial for the development of efficient ultrathin single-junction and tandem perovskite solar cells.

The epitaxy of GaAs/Si(001) has been carried out via inserting different buffer layers and different SLSs by MOCVD. High quality epilayers were obtained by AlAs buffer layer and GaAs0.85P0.15/GaAs SLS.

The growth of GaAs epilayers on silicon substrates with a thin amorphous silicon (a-Si) buffer layer by metalorganic chemical vapor deposition is investigated in detail. Combining with the two-step growth method, the growth conditions of the a-Si buffer layer are optimized for growth of high-quality GaAs/Si epilayers. The a-Si buffer layer exhibits the best effect with thickness of 1.8 nm and growth temperature of 620°C. It is found that the introduction of this a-Si layer on Si substrates effectively reduces the dislocation density in GaAs/Si films. As compared with the dislocation density of 5 × 107 cm−2 in the GaAs/Si sample without the a-Si layer, a density of 3 × 105 cm−2 is achieved in the sample with the a-Si layer, and the defect reduction mechanism is discussed in detail.

The growth of GaAs epilayers on silicon substrates with multiple layers of InAs quantum dots (QDs) as dislocation filters by metalorganic chemical vapor deposition (MOCVD) is investigated in detail. The growth conditions of single and multiple layers of QDs used as dislocation filters in GaAs/Si epilayers are optimized. It is found that the insertion of a five-layer InAs QDs into the GaAs buffer layer effectively reduces the dislocation density of GaAs/Si film. Compared with the dislocation density of 5×107 cm−2 in the GaAs/Si sample without QDs, a density of 2×106 cm−2 is achieved in the sample with QD dislocation filters.

In this study, metamorphic growth of GaAs on Si(001) substrate was investigated via three-step growth in a low-pressure metal organic chemical vapor deposition reactor. Three-step growth was achieved by simply inserting an intermediate temperature GaAs layer between the low temperature GaAs nucleation layer and the high temperature GaAs epilayer. Compared with conventional two-step growth, three-step growth could further reduce surface roughness and etch pit density. By combining three-step growth with thermal-cycle annealing, the authors have grown a 1.8-μm-thick GaAs epilayer with root mean square roughness of only 1.8 and 0.73 nm in 10 × 10 μm2 and 2 × 2 μm2 scanning areas, respectively. The threading dislocation density of the 1.8-μm-thick GaAs epilayer was as low as 1.1 × 107 cm−2, as calculated directly from the double crystal x-ray diffraction ω-scan full width at half maximum of the GaAs diffraction peak. The corresponding etch pit density was only 3 × 106 cm−2.

The epitaxial growth of GaAs on patterned Si(001) substrates by MOCVD is presented. Effect of growth temperature and V/III ratio on coalescence is investigated. Meanwhile, changing total pressure can reduce the polycrystals generated on mask.

A corrected two-section model of concentration profiles for B+, P+ and As+ implanted into silicon is given. The diffusion and electrical activation dependent on the concentration of Si+ in GaAs is considered. Using the progressive compensation method (PCM) to find the optimum quantities for implantation, a special program IMSOP has been written that quickly finds the best conditions to make any wanted dopant profile, e.g. an even profile and a double-peak profile. The simulated results are consistent with the experimental values. Using 29Si+ implanted GaAs wafer designed using IMSOP, fairly good MESFETs have been fabricated.