Nucleation and bulk growth control for high efficiency silicon ingot casting

Grain control in directional solidification of photovoltaic silicon

“…However, in the dendritic casting method [4,22], due to the faster /112S dendrite growth, bigger grains could be obtained. Nevertheless, the implementation of the dendrite casting method in the commercial furnace is not so easy [27]. For silicon, the undercooling for homogeneous nucleation could be as high as 420 K [29], but that for heterogeneous nucleation with nitrite particles was usually much less than 20 K [30,31].…”

“…The non-coherent grain boundaries were also less. Nevertheless, as mentioned in a recent review by Zhang et al [27] that in mass production, not only is the crystal quality important, but also the robustness of the growth conditions, as well as and high throughput and yield, are required. In practice, so far, the reproducibility of the growth controlled by undercooling is indeed a great concern.…”

Defect recognition by means of light and electron probe techniques for the characterization of mc-Si wafers and solar cells

“…These defects act as traps for the minority carriers, killing the minority carrier lifetime (t), and shortening the carrier diffusion length (L diff ), which negatively affects the energy conversion efficiency [2,3]. Some new approaches have appeared in recent years, trying to decrease the number of grains and GBs in mc-Si [4], in particular, the quasi-mono Si (qm-Si) growth, in which the use of c-Si as seeds in a conventional casting furnace leads to large mono-crystalline areas, is attracting a great deal of attention [5]. Other approaches aiming to reduce the cost of the raw material run in parallel; in particular, the use of upgraded metallurgical grade silicon (UMG-Si), which faces the problems related to the high number of metallic impurities [6].…”

Local design of the hot-zone in an industrial seeded directional solidification furnace for quasi-single crystalline silicon ingots

“…This technology is therefore a promising alternative to the traditional high cost Cz and float zone methods [3]. In a seeded DS process, precise control of the thermal field within the silicon domain is vital for preserving the seeds and maintaining the quasi-single crystal structure all the way to the top of the silicon ingot [4]. Moreover, the control of the thermal field in the furnace is related to energy consumption, which is clearly of interest to crystal growers.…”

“…Zhang et al [4] numerically examined the effects of holes in the top insulation and a gas shield on the gas flow in a Jinggong JJL500 furnace. Delannoy et al [5] studied the effect of two different diameter legs in an ECM furnace on the thermal gradient in the silicon charge and growth rate by means of a transient 3D numerical model.…”