Effect of grain boundary character of multicrystalline Si on external and internal (phosphorus) gettering of impurities

Abstract

We investigated the effect of the grain boundary (GB) character of multicrystalline Si (mc-Si) on the efficiency of external and internal gettering of impurities during phosphorus diffusion gettering (PDG). We utilized seed crystals with an artificially designed GB configuration to grow mc-Si ingots with different artificial GB characters. PDG combined with an originally developed multiple-cycle gettering technique at low temperature was introduced on intentionally Fe-contaminated mc-Si samples to enhance external and internal gettering. A significant positive PDG effect was observed after PDG combined with the multiple-cycle technique, as evidenced by the increase in lifetimes after PDG. A bright cloud-like photoluminescence signal around contaminated GBs was observed for artificial Σ5-GBs and tilt-GBs after PDG, suggesting the enhancement of the internal gettering efficiency by leaving a cleaner area around the GBs. This result suggests the importance of the control of crystal defect character as well as impurities in mc-Si ingots, which could strongly affect the PDG efficiency.

Lattice distortion induced site dependent carbon gettering at twin boundaries in silicon

“…Due to the low production cost, multi-crystalline Si (mc-Si) now accounts for over 50% of the feedstock materials for photovoltaic solar cells [1,2]. However, solar cells based on casting mc-Si has a relatively high concentration of alien impurities [3][4][5][6], including transition metals (e.g.…”

External Gettering of Metallic Impurities by Black Silicon Layer

“…There are two different types of gettering, namely, external and internal. [1,2] In internal gettering, impurities inside the Si substrate form alternative species, such as precipitates, which are less recombination active. External gettering is based on the creation of gettering centers on the back or near surfaces of Si substrates (external planar and lateral gettering, respectively).…”

Temperature sensitivity maps of silicon wafers from photoluminescence imaging: The effect of gettering and hydrogenation

“…Gettering and hydrogenation play key roles in the performance enhancement of Si solar cells 18–25 . They commonly occur during standard solar cell fabrication processes, specifically phosphorus diffusion, silicon nitride deposition and the subsequent metallisation firing processes.…”

“…Gettering and hydrogenation play key roles in the performance enhancement of Si solar cells. [18][19][20][21][22][23][24][25] They commonly occur during standard solar cell fabrication processes, specifically phosphorus diffusion, silicon nitride deposition and the subsequent metallisation firing processes. These processes not only improve the electrical properties of PV devices but are also expected to have a considerable influence on their TCs due to their impacts on the voltage.…”