Si surface passivation by SiO_x : H films deposited by a low-frequency ICP for solar cell applications

Abstract

Hydrogenated silicon suboxide (SiO x : H) thin films are fabricated by a low-frequency inductively coupled plasma of hydrogen-diluted SiH4 + CO2 at a low temperature (100 °C). Introduction of a small amount of oxygen into the film results in a predominantly amorphous structure, wider optical bandgap, increased H content, lower conductivity and higher activation energy. The minority carrier lifetime in the SiO x : H-passivated p-type Si substrate is up to 428 µs with a reduced incubation layer at the interface. The associated surface recombination velocity is as low as 70 cm s−1. The passivation behaviour dominantly originates from the H-related chemical passivation. The passivation effect is also demonstrated by the excellent photovoltaic performance of the heterojunction solar cell with the SiO x : H-based passivation and emitter layers.

Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

“…In order to further investigate the influence of CO 2 partial pressure on the film property, FTIR analysis was carried out. The results are shown in bonding group is not observable, which is similar to other a-SiO :H(i) thin films commonly reported in the literature [15,19,37]. The Si-C or C-H bonding configuration is also not clearly visible in the spectra due to extremely small inclusion of C atoms in the film [50,51].…”

“…It is interesting to observe that the Si-O-Si stretching peak at 1107 cm −1 becomes more significant with higher compared to that at 1053 cm −1 . Jana et al [37] and Zhou et al [15] associate these peaks to Si-H(Si 3− O ) with = 2 and 1, respectively, according to random bonding model [53]. The increase of peak intensity at 1107 cm −1 indicates an increase of Si-H(SiO 2 ) bonding concentration.…”

“…PECVD hydrogenated intrinsic amorphous silicon suboxide (a-SiO :H(i)) thin films are emerging as an alternative 2 International Journal of Photoenergy to replace a-Si:H(i) as passivation layer in HET solar cells. Its excellent passivation quality and optical property has been demonstrated by several groups in recent years [15][16][17][18][19]. Notably, Mueller et al [16,18,20,21] have shown a record of high passivation quality on highly doped wafers using direct capacitively coupled plasma (CCP).…”

Investigation of Wide Process Temperature Window for Amorphous Silicon Suboxide Thin-Film Passivation Deposited by Inductively Coupled PECVD

“…However, due to the onset of H effusion, effects of these two phenomena cannot be distinguished in this case. Compared with Zhou et al [40], who showed a crystalline interfacial layer of about 30 nm, the suppression of such layer formation by using the optimal deposition conditions in this paper is the key to achieving high passivation quality and an improved process window.…”

Surface Passivation Schemes for High-Efficiency c-Si Solar Cells - A Review

“…To overcome bulk lifetime degradation, a low-temperature SiO x deposition by PECVD has been studied by different groups [33][34][35] for surface passivation. Another option for the synthesis of SiO x is a chemical oxidation of the Si surface using nitric acid (HNO 3 ).…”