体缺陷主导的少子寿命衰减：光伏用n型Cz硅片高温行为机理与抑制策略

doi:10.16553/j.cnki.issn1000-985x.2025.0259

摘要/Abstract

摘要： 硅片少子寿命在经历光伏电池高温工艺后普遍出现急剧衰减，这严重制约了电池效率的进一步提升。为阐明其潜在机理，本研究通过系统的热处理实验，结合少子寿命、光致发光（PL）、傅里叶变换红外光谱等表征手段，对光伏用n型直拉（Cz）硅片的高温行为进行了研究。结果表明，高温处理导致的少子寿命与PL强度大幅衰减主要源于体复合缺陷的显著增加，与表面状态及工艺气氛关联较弱。此外，热处理过程中硅片内间隙氧向沉淀氧转化，且在氧气氛围下伴有环境氧的净渗入。综合分析表明，原生硅片中存在的氧沉淀胚核在高温工艺中被激活并生长，形成具有高复合活性的氧沉淀，这是导致少子寿命衰减的主要原因。基于“氧沉淀胚核选择性激活与生长”的机理，本研究提出通过优化晶体冷却热历史抑制胚核生成，以及利用快速热退火消融已有缺陷的两种优化策略。

关键词: n型直拉硅; 少子寿命; 高温衰减; 氧沉淀; 快速热退火

Abstract: The minority carrier lifetime of silicon wafers generally decays sharply after high-temperature processes in solar cell fabrication， significantly limiting further improvements in cell efficiency. To elucidate the underlying mechanism， this study systematically investigated the high-temperature behavior of photovoltaic-grade n-type Czochralski （Cz） silicon wafers through controlled heat treatment experiments， combined with multi-scale characterization techniques including minority carrier lifetime， photoluminescence（PL）， and Fourier-transform infrared spectroscopy. The results demonstrate that the significant degradation in both minority carrier lifetime and PL intensity after high-temperature treatment primarily stems from a substantial increase in bulk recombination defects， with surface conditions and process atmosphere playing a minor role. Furthermore， during heat treatment， interstitial oxygen within the silicon wafer converts into precipitated oxygen， accompanied by net inward diffusion of ambient oxygen in an oxygen-rich atmosphere. Comprehensive analysis indicates that oxygen precipitate nuclei pre-existing in the as-grown silicon wafers become activated and grow during high-temperature process， forming oxygen precipitates with high recombination activity， which is identified as the main cause of minority carrier lifetime degradation. Based on the mechanism of ‘selective activation and growth of oxygen precipitate nuclei’， this study proposes two optimization strategies： suppressing nucleus formation by optimizing the crystal cooling thermal history and eliminating existing defects through rapid thermal annealing.

Key words: n-type Czochralski silicon; minority carrier lifetime; high-temperature degradation; oxygen precipitate; rapid thermal annealing

中图分类号:

O786

王鹏飞, 张远方, 欧子杨, 王钊, 陈占仓, 林瑶. 体缺陷主导的少子寿命衰减：光伏用n型Cz硅片高温行为机理与抑制策略[J]. 人工晶体学报, 2026, 55(4): 619-626.

WANG Pengfei, ZHANG Yuanfang, OU Ziyang, WANG Zhao, CHEN Zhancang, LIN Yao. Bulk-Defect Dominated Minority Carrier Degradation: Mechanisms and Suppression Strategies for High-Temperature Behavior of Photovoltaic n-Type Czochralski Silicon Wafers[J]. Journal of Synthetic Crystals, 2026, 55(4): 619-626.

图/表 7

图1 少子寿命与样片厚度的关系（BCT-400与WCT-120测试）

Fig.1 Relationship between minority carrier lifetime and sample thickness （measured by BCT-400 and WCT-120）

表1 不同热处理条件下的少子寿命变化

Table 1 Minority carrier lifetime variation under different heat treatment conditions

Group	Temperature/℃	Gas	Oxygenation duration/s	τ_eff/μs			Instrument for τ_eff
Group	Temperature/℃	Gas	Oxygenation duration/s	Before heat treatment	After heat treatment	After surface removal	Instrument for τ_eff
1A	850	O₂	9 500	3 853	132	—	BCT-400
1B	1 000	O₂	9 500	3 787	133	119	BCT-400
2A	1 000	O₂	9 500	2 775	169	119	BCT-400
2B	1 000	N₂	0	2 840	131	—	BCT-400
3A	1 000	O₂	1 000	9 583	26	—	WCT-120
3B	1 000	O₂	2 000	10 642	11	—	WCT-120

图2 热处理前后PL强度变化

Fig.2 Changes in PL intensity before and after heat treatment

图3 热处理前、后氧含量与化学状态变化

Fig.3 Changes in oxygen content and chemical state before and after heat treatment

图4 硅结晶冷却过程中空位浓度演变及缺陷形成示意图

Fig.4 Schematic diagram of vacancy concentration evolution and defect formation during post-crystallization cooling of silicon

图5 腐蚀硅片的微缺陷分布图

Fig.5 Microdefect distribution of etched silicon wafer

图6 不同处理工艺后的硅片PL检测结果。（a）A组（制绒+钝化），B组（制绒+硼扩+钝化），C组（制绒+硼扩+磷扩+钝化），D组（制绒+N2氛围缺陷消融+硼扩+磷扩+钝化），以及E组（制绒+O2氛围缺陷消融+硼扩+磷扩+钝化）各组平均PL强度；（b）各组第一张硅片的PL图

Fig. 6 PL test results of silicon wafers after different treatment processes. （a） Average PL intensity of A （texturing+passivation）， B （texturing+boron diffusion+passivation）， C （texturing+boron diffusion+phosphorus diffusion+passivation）， D （texturing+defects-ablation in N2+boron diffusion+phosphorus diffusion+passivation）， E （texturing+defects-ablation in O2+boron diffusion+phosphorus diffusion+passivation）；（b） PL images of first wafer in each group

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