Al2O3/SiON stack layers for effective surface passivation and anti-reflection of high efficiency n-type c-Si solar cells. (9th January 2017)

• Record Type: Journal Article
• Authors: Nguyen, Huong Thi Thanh; Balaji, Nagarajan; Park, Cheolmin; Triet, Nguyen Minh; Le, Anh Huy Tuan; Lee, Seunghwan; Jeon, Minhan; Oh, Donhyun; Dao, Vinh Ai; Yi, Junsin
• Is Part Of: Semiconductor science and technology. Volume 32:Number 2(2017:Feb.)
• Publication Date: 2017-01-09
• Subjects: silicon oxynitride -- Al2O3/SiON stack -- negative fixed charge -- surface passivation; Semiconductors -- Periodicals; 621.38152
• DOI: 10.1088/1361-6641/32/2/025005
• Languages: English
• ISSNs: 0268-1242

Abstract

Abstract: Excellent surface passivation and anti-reflection properties of double-stack layers is a prerequisite for high efficiency of n-type c-Si solar cells. The high positive fixed charge ( Q f ) density of N-rich hydrogenated amorphous silicon nitride (a-SiNx :H) films plays a poor role in boron emitter passivation. The more the refractive index ( n ) of a-SiNx :H is decreased, the more the positive Q f of a-SiNx :H is increased. Hydrogenated amorphous silicon oxynitride (SiON) films possess the properties of amorphous silicon oxide (a-SiOx ) and a-SiNx :H with variable n and less positive Q f compared with a-SiNx :H. In this study, we investigated the passivation and anti-reflection properties of Al2 O3 /SiON stacks. Initially, a SiON layer was deposited by plasma enhanced chemical vapor deposition with variable n and its chemical composition was analyzed by Fourier transform infrared spectroscopy. Then, the SiON layer was deposited as a capping layer on a 10 nm thick Al2 O3 layer, and the electrical and optical properties were analyzed. The SiON capping layer with n = 1.47 and a thickness of 70 nm resulted in an interface trap density of 4.74 = 10 10 cm −2 eV −1 and Q f of −2.59 = 10 12 cm −2 with a substantial improvement in lifetime of 1.52 ms after industrial firing. The incorporation of an Al2 O3 /SiON stack on the front side of the n-type solar cells results in an energy conversion efficiency of 18.34% compared to the one with Al2 O3 /a-SiNx :H showing 17.55% efficiency. The short circuit current density and open circuit voltage increase by up to 0.83 mA cm −2 and 12 mV, respectively, compared to the Al2 O3 /a-SiNx :H stack on the front side of the n-type solar cells due to the good anti-reflection and front side surface passivation.