Search | Engineering

资源类型

期刊论文 2

年份

2017 2

关键词

检索范围：

排序：展示方式：

Laser enhanced gettering of silicon substrates

Daniel CHEN,Matthew EDWARDS,Stuart WENHAM,Malcolm ABBOTT,Brett HALLAM

《能源前沿（英文）》 2017年第11卷第1期页码 23-31 doi: 10.1007/s11708-016-0441-7

摘要： One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry highly reliant on heavily doped phosphorus diffusions as a source of gettering, the transition to selective emitter structures would require new alternative methods of impurity extraction. In this paper, a novel laser based method for gettering is investigated for its impact on commercially available silicon wafers used in the manufacturing of solar cells. Direct comparisons between laser enhanced gettering (LasEG) and lightly-doped emitter diffusion gettering demonstrate a 45% absolute improvement in bulk minority carrier lifetime when using the laser process. Although grain boundaries can be effective gettering sites in multicrystalline wafers, laser processing can substantially improve the performance of both grain boundary sites and intra-grain regions. This improvement is correlated with a factor of 6 further decrease in interstitial iron concentrations. The removal of such impurities from multicrystalline wafers using the laser process can result in intra-grain enhancements in implied open-circuit voltage of up to 40 mV. In instances where specific dopant profiles are required for a diffusion on one surface of a solar cell, and the diffusion process does not enable effective gettering, LasEG may enable improved gettering during the diffusion process.

关键词： gettering multicystaline silicon impurities laser doping

HTML PDF 收藏

Impact of thermal processes on multi-crystalline silicon

Moonyong KIM,Phillip HAMER,Hongzhao LI,David PAYNE,Stuart WENHAM,Malcolm ABBOTT,Brett HALLAM

《能源前沿（英文）》 2017年第11卷第1期页码 32-41 doi: 10.1007/s11708-016-0427-5

摘要： Fabrication of modern multi-crystalline silicon solar cells involves multiple processes that are thermally intensive. These include emitter diffusion, thermal oxidation and firing of the metal contacts. This paper illustrates the variation and potential effects upon recombination in the wafers due to these thermal processes. The use of light emitter diffusions more compatible with selective emitter designs had a more detrimental effect on the bulk lifetime of the silicon than that of heavier diffusions compatible with a homogenous emitter design and screen-printed contacts. This was primarily due to a reduced effectiveness of gettering for the light emitter. This reduction in lifetime could be mitigated through the use of a dedicated gettering process applied before emitter diffusion. Thermal oxidations could greatly improve surface passivation in the intra-grain regions, with the higher temperatures yielding the highest quality surface passivation. However, the higher temperatures also led to an increase in bulk recombination either due to a reduced effectiveness of gettering, or due to the presence of a thicker oxide layer, which may interrupt hydrogen passivation. The effects of fast firing were separated into thermal effects and hydrogenation effects. While hydrogen can passivate defects hence improving the performance, thermal effects during fast firing can dissolve precipitating impurities such as iron or de-getter impurities hence lower the performance, leading to a poisoning of the intra-grain regions.

关键词： gettering grain boundaries hydrogen impurities oxidation passivation solar cell