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Dislocation behavior at the interface between a heavily B-doped or B and Ge codoped Si seed and the grown crystal using Czochralski Si crystal growth under various seeding temperatures was investigated. When the diameter of the grown crystal just below the interface was larger than that of the seed, dislocation were generated in the grown crystal from the edge of the interface due to incomplete seeding. It was found that no dislocations were generated near the interface when the diameter was smaller than that of the seed, and the smaller diameter was simply realized by seeding at a higher temperature before pulling up the crystal. A practical industrial-scale dislocation-free Si crystal 8 in in diameter was successfully grown without a thin neck by suppressing dislocations not only due to thermal shock and lattice misfit but also due to incomplete seeding. [Copyright &y& Elsevier]

Dislocation-free heavily Ge-doped Czochralski (CZ)-Si crystal growth using a heavily Ge-doped Si seed has been investigated. Dislocations due to thermal shock were suppressed in a seed 7×7 mm2 in cross-section when Ge concentration in the seed exceeded 9×1019 atoms/cm3. When Ge concentration in the grown crystal was 5.7×1020 atoms/cm3, cellular growth occurred, and this concentration was a limit for heavily Ge-doped Si single crystal growth with a growth rate of about 1 mm/min. Resistivity in the crystal results in B or P doping could be controlled precisely in spite of using a heavily Ge-doped Si seed for growing a dislocation-free CZ-Si crystal without Dash necking. [Copyright &y& Elsevier]

Mixed seeds of fused quartz particles and silicon particles were laid at the bottom of the crucible to assist the growth of multicrystalline silicon crystals. The full melting process was used, and then we found that the grown crystals had higher quality. The effect of mixed seeds on the growth of multicrystalline silicon was studied. The results showed that fine and uniform initial grains could be obtained by mixed seeds assisting the growth of crystals. Increasing the number of grain boundaries can better release thermal stress and inhibit the proliferation and diffusion of dislocations. The defect density of multicrystalline silicon decreased and the minority carrier lifetime increased, thus improving the conversion efficiency of multicrystalline silicon cells. [ABSTRACT FROM AUTHOR]

The performance of high‐performance multicrystalline silicon ingots is studied as a function of fused quartz seed particle size. Four kinds of Si ingots are grown using fused quartz particles having four distinct particle sizes, seed Nos. 1–4, corresponding to mesh sizes of 10–30, 30–50, 50–70, and 70–100, respectively. Each seed type is employed to have the same particle density area of ≈220 particles per cm2. The experimental results show that the Si ingot grown using 50–70 mesh seeds (seed No. 3) has the best uniformity of initial nucleation and subsequent grains, resulting in the lowest density of dislocation clusters. The Si ingots are cut into bricks and Si wafers are sliced from different positions of each brick and further studied. As a result, the average conversion efficiency is the highest for the ingot grown using No. 3 seeds (50–70 mesh) at 18.34%, ≈0.22% (absolute value) higher than that observed when employing 10–30 mesh seeds (seed No. 1, 18.12%). Four kinds of Si ingots are grown using fused quartz particles, seed Nos. 1–4, corresponding to mesh sizes of 10–30, 30–50, 50–70 and 70–100, respectively. The experimental results show that the Si ingot grown in the presence of 50–70 mesh seeds has the best crystal quality. [ABSTRACT FROM AUTHOR]

Oxygen is one of the highest-concentration impurities in single crystals grown by the Czochralski (CZ) process, and seriously impairs the quality of the Si wafer. In this study, computer simulations were applied to design a new CZ system. A more appropriate thermal field was acquired by optimization of the heater structure. The simulation results showed that, compared with the conventional system, the oxygen concentration in the newly designed CZ system was reduced significantly throughout the entire CZ process because of the lower crucible wall temperature and optimized convection. To verify the simulation results, experiments were conducted on an industrial single-crystal furnace. The experimental results showed that the oxygen concentration was reduced significantly, especially at the top of the CZ-Si ingot. Specifically, the oxygen concentration was 6.19 × 10 17  atom/cm 3 at the top of the CZ-Si ingot with the newly designed CZ system, compared with 9.22 × 10 17  atom/cm 3 with the conventional system. Corresponding light-induced degradation of solar cells based on the top of crystals from the newly designed CZ system was 1.62%, a reduction of 0.64% compared with crystals from the conventional system (2.26%). [ABSTRACT FROM AUTHOR]

A transient global model was established to investigate the effect of the raise velocities of the partition block on the crystal growth rate, the crystal–melt (C–M) interface and the thermal stress distribution during the solidification process. The simulation results showed that among the different raise velocities of the partition block, initially slowly raising and then rapidly raising the partition block was the most favorable for the solidification process. A slightly convex C–M interface and low thermal stress distribution were obtained, and a fast crystal growth rate was also achieved. Thus, this design was implemented in casting experiments, and the experimental results indicated that this design was beneficial for optimizing the C–M interface in the solidification process. The average conversion efficiencies of high-performance multi-crystalline silicon solar cells was about 0.13% higher with this design (18.18%) than with a fixed partition block design (18.05%). [ABSTRACT FROM AUTHOR]

For the seed-assisted casting process for silicon ingots, different partition blocks were designed in the directional solidification (DS) furnaces to preserve the seed crystals and optimize the thermal field in the hot-zone. A transient global model was established to investigate the effects of different partition blocks during the solidification process. The simulation results showed that the partition blocks can significantly influence the temperature distributions and the melt flow fields. From the designed partition blocks, the movable partition block was more favorable for the seed-assisted DS process. A suitable temperature gradient and a flat seed-melt (s-m) interface were obtained, which facilitated the preservation of seed crystals effectively, and an optimized crystal-melt (c-m) interface was achieved as well. One of the designs of the movable partition blocks was implemented in quasi-mono crystalline silicon casting experiments and it has been confirmed that the designed movable partition block was helpful for the improvement of the single crystal area. [ABSTRACT FROM AUTHOR]

Abstract: An insulation partition was designed in a seeded directional solidification (DS) furnace of industrial-size to produce quasi-single crystalline silicon ingot for solar cells of high efficiency. We used a transient global model to study the effects of the insulation partition block on the temperature and thermal stress fields in the solidified silicon ingot during the solidification process. We validated the transient global model by comparing the calculations with the experimental measurements. Simulation results show that an insulation partition block can significantly reduce the total heating power consumption and influence the temperature and velocity fields in the silicon melt. We also found that the melt-crystal interface (m–c interface) shape changes from concave to convex to the melt with a larger crystal growth rate with an insulation partition, while it always remains flat with a smaller crystal growth rate without a partition block. The axial temperature gradient and thermal stress in the grown silicon crystal increased with a partition block. The solar cells from the grown quasi-single crystalline silicon ingot exhibited higher short-circuit current (Isc) and open-circuit voltage (Voc). The average conversion efficiency of solar cells is increased to 17.8% and about 1.2% more than that based on mc-Si ingot from the conventional furnace. [Copyright &y& Elsevier]