钝化
材料科学
硅
载流子寿命
硅烷
化学气相沉积
薄脆饼
等离子体增强化学气相沉积
退火(玻璃)
非晶硅
纳米复合材料
太阳能电池
拉曼光谱
无定形固体
分析化学(期刊)
晶体硅
化学工程
光电子学
纳米技术
复合材料
化学
图层(电子)
光学
结晶学
物理
色谱法
工程类
作者
Thomas Mueller,Stefan Schwertheim,W. R. Fahrner
摘要
A passivation scheme, featuring nanocomposite amorphous silicon suboxides (a-SiOx:H) is investigated and analyzed in this work. The a-SiOx:H films are deposited by high-frequency plasma-enhanced chemical-vapor deposition via decomposition of silane (SiH4), carbon dioxide (CO2), and hydrogen (H2) as source gases. The plasma deposition parameters of a-SiOx:H films are optimized in terms of effective lifetime, while the oxygen content and the resulting optical band gap EG of the a-SiOx:H films are controlled by varying the CO2 partial pressure χO=[CO2]/([CO2]+[SiH4]). Postannealing at low temperatures of those films shows a beneficial effect in form of a drastic increase of the effective lifetime. This improvement of the passivation quality by low temperature annealing for the a-SiOx:H likely originates from defect reduction of the film close to the interface. Raman spectra reveal the existence of Si–(OH)x and Si–O–Si bonds after thermal annealing of the layers, leading to a higher effective lifetime, as it reduces the defect absorption of the suboxides. The surface passivation quality of a-SiOx:H within both n-type and p-type silicon has been studied as a function of injection level. Record high effective lifetime values of 4.7 ms on 1 Ω cm n-type float zone (FZ) wafers and 14.2 ms on 130 Ω cm p-type FZ wafers prove the applicability for a surface passivation of silicon wafers applicable to any kind of silicon-based solar cells. The effective lifetime values achieved on a highly doped crystalline wafer (1 Ω cm resistivity) appears to be the highest value ever reported. Samples prepared in this way feature a high quality passivation yielding effective lifetime values exceeding those of record SiO2 and SiNx passivation schemes.
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