Plasma enhanced chemical vapor deposition of excellent a-Si:H passivation layers for a-Si:H/c-Si heterojunction solar cells at high pressure and high power

doi:10.1007/s11708-016-0437-3

Front. Energy

2017, Vol. 11

Issue (1) : 85-91 https://doi.org/10.1007/s11708-016-0437-3

RESEARCH ARTICLE

Plasma enhanced chemical vapor deposition of excellent a-Si:H passivation layers for a-Si:H/c-Si heterojunction solar cells at high pressure and high power

Lei ZHAO¹,Wenbin ZHANG³,Jingwei CHEN²,Hongwei DIAO²,Qi WANG³(

),Wenjing WANG¹

¹. Key Laboratory of Solar Thermal Energy and Photovoltaic System of Chinese Academy of Sciences, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China
². Key Laboratory of Solar Thermal Energy and Photovoltaic System of Chinese Academy of Sciences, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
³. GCL System Integration Technology Co. Ltd, Shanghai 201406, China

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Abstract

The intrinsic a-Si:H passivation layer inserted between the doped a-Si:H layer and the c-Si substrate is very crucial for improving the performance of the a-Si:H/c-Si heterojunction (SHJ) solar cell. The passivation performance of the a-Si:H layer is strongly dependent on its microstructure. Usually, the compact a-Si:H deposited near the transition from the amorphous phase to the nanocrystalline phase by plasma enhanced chemical vapor deposition (PECVD) can provide excellent passivation. However, at the low deposition pressure and low deposition power, such an a-Si:H layer can be only prepared in a narrow region. The deposition condition must be controlled very carefully. In this paper, intrinsic a-Si:H layers were prepared on n-type Cz c-Si substrates by 27.12 MHz PECVD at a high deposition pressure and high deposition power. The corresponding passivation performance on c-Si was investigated by minority carrier lifetime measurement. It was found that an excellent a-Si:H passivation layer could be obtained in a very wide deposition pressure and power region. Such wide process window would be very beneficial for improving the uniformity and the yield for the solar cell fabrication. The a-Si:H layer microstructure was further investigated by Raman and Fourier transform infrared (FTIR) spectroscopy characterization. The correlation between the microstructure and the passivation performance was revealed. According to the above findings, the a-Si:H passivation performance was optimized more elaborately. Finally, a large-area SHJ solar cell with an efficiency of 22.25% was fabricated on the commercial 156 mm pseudo-square n-type Cz c-Si substrate with the open-circuit voltage (V_oc) of up to 0.732 V.

Keywords PECVD high pressure and high power a-Si:H microstructure passivation heterojunction solar cell

Corresponding Author(s): Qi WANG

Just Accepted Date: 19 October 2016 Online First Date: 09 November 2016 Issue Date: 16 November 2016

Cite this article:

Lei ZHAO,Wenbin ZHANG,Jingwei CHEN, et al. Plasma enhanced chemical vapor deposition of excellent a-Si:H passivation layers for a-Si:H/c-Si heterojunction solar cells at high pressure and high power[J]. Front. Energy, 2017, 11(1): 85-91.

URL:

https://academic.hep.com.cn/fie/EN/10.1007/s11708-016-0437-3
https://academic.hep.com.cn/fie/EN/Y2017/V11/I1/85

Fig.1 Effective minority carrier lifetime ( τ eff ) and maximum limit of effective surface recombination velocity ( S eff, max ) obtained via a-Si:H passivation layers deposited at different conditions

(a) Deposition power is 300 W and deposition pressure is varied from 133 to 665 Pa; (b) deposition pressure is 399 Pa and deposition power is varied from 100 to 900 W

Fig.2 Raman spectra of the a-Si:H thin films deposited on the quartz substrates at different conditions

(a) Deposition power is 300 W and deposition pressure is varied from 133 to 665 Pa; (b) deposition pressure is 399 Pa and deposition power is varied from 100 W to 900 W

Fig.3 FTIR spectra of the a-Si:H thin films deposited on the c-Si substrates at different conditions

(a)Deposition power is 300 W and deposition pressure is varied from 133 to 665 Pa; (b) deposition pressure is 399 Pa and deposition power is varied from 100 to 900 W

Fig.4 Microstructure parameter (R^*) of a-Si:H thin films obtained according to FTIR spectra

Fig.5 Representative transmission electron microscopy (TEM) photograph for obtained compact a-Si:H layer on c-Si substrate

Fig.6 Hydrogen content (C_H) in a-Si:H films deposited at a pressure of 399 Pa with power varied from 100 to 900 W

Fig.7 Highest effective minority carrier lifetime (t_eff) achieved by optimized deposition condition at a relatively high pressure and high power

Fig.8 Light current-voltage (I-V) performance of optimized a-Si:H/c-Si heterojunction (SHJ) solar cell obtained on commercial 156 mm pseudo-square n-type Cz c-Si substrate

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