Suppression of the epitaxial growth of Si films in Si heterojunction solar cells by the formation of ultra-thin oxide layers

Abstract

The epitaxial growth of silicon (Si) films during the catalytic chemical vapor deposition (Cat-CVD) of intrinsic amorphous Si (i-a-Si) passivation films on crystalline Si (c-Si) wafers is suppressed by the oxidation of c-Si surfaces simply by dipping the c-Si wafers in hydrogen peroxide (H 2 O 2 ). This oxidation treatment is also effective for (111)-oriented c-Si surfaces particularly at high a-Si deposition temperatures. The suppression of the epitaxial growth leads to the better effective minority carrier lifetime (τ eff ) of c-Si wafers passivated with Cat-CVD i-a-Si films. SHJ solar cells show remarkably high open-circuit voltage (V oc ) exceeding 0.7 V. These results clearly show the effectiveness of the insertion of SiO x layers on the improvement in Cat-CVD a-Si/c-Si interfaces.

Ultra-thin silicon oxide layers on crystalline silicon wafers: Comparison of advanced oxidation techniques with respect to chemically abrupt SiO 2 /Si interfaces with low defect densities

“…In other studies of conventional thermal oxides values of 10-30 % were observed[6]. Thus, formation of suboxides at the SiO 2 /Si interface turned out to be effectively suppressed (for TPO, RTO, WC-NAOS, PO) indicating a chemically abrupt interface.…”

“…Typical examples are passivated contacts in silicon solar cells [1,2], intermediate layers in metal-insulatorsemiconductor (MIS) solar cells [3], passivation of the amorphous/crystalline silicon (a-Si:H/c-Si) heterojunction [4][5][6], and barrier layer in silicon-based single and multi-junction quantum well solar cells [7,8]. Very recently, 25.1 % efficiency was achieved on a both sides-contacted Si solar cell featuring tunnel oxide passivated contacts [9].…”

Intrinsic Amorphous Silicon Bilayers for Effective Surface Passivation in Silicon Heterojunction Solar Cells: A Comparative Study of Interfacial Layers

“…[1,14,15] The growth condition of the i-layer has to be controlled carefully for preventing epitaxial growth at the a-Si:H/c-Si interface, which is generally detrimental for surface passivation. [16][17][18] To this end, interfacial layers such as porous (underdense) a-Si:H layers, [4,[19][20][21] a-Si:H alloys, including amorphous silicon oxides and carbides (a-SiO X :H [22,23] and a-SiC X :H [24] ), and very thin oxides [25,26] have been investigated. In addition, hydrogen dilution of SiH 4 plasma [18,27,28] has a significant impact on the surface passivation.…”

The Effect of Annealing Temperature on the Structural and Optical Properties of Si/SiO2 Composites Synthesized by Thermal Oxidation of Silicon Wafers

“…The oxidation of silicon surfaces shows promising properties that have made them the focus of many research groups , which have sought to employ various silicon oxidation techniques in the fabrication of semiconductor devices. These oxidized layers can be used as a key ingredient in creating many electronic devices such as, passivated contacts in silicon solar cells [1,2], multi-junction quantum well solar cells [7,8], and barrier layer in silicon-based single and passivation of the amorphous/crystalline Si (a-Si:H/c-Si) heterojunction [4][5][6], etc.…”