Tunnel silicon oxide passivated contact solar cell and preparation method thereof

Abstract

The invention provides a solar cell. The solar cell comprises a silicon wafer, a passivated tunnel layer and a doping thin film silicon layer, wherein passivated tunnel layer is arranged between the silicon wafer and the doping thin film silicon layer, the passivated tunnel layer is one of a silicon oxide / silicon oxynitride gradient lamination layer, a silicon oxynitride / silicon nitride gradient lamination layer and a silicon oxide / silicon oxynitride / silicon nitride gradient lamination layer, the silicon oxynitride is nitrogen doping silicon oxide or oxygen doping silicon nitride, and the nitrogen concentration of the silicon oxide / silicon oxynitride gradient lamination layer, the silicon oxynitride / silicon nitride gradient lamination layer and the silicon oxide / silicon oxynitride / silicon nitride gradient lamination layer is gradiently reduced from a part far away from a silicon wafer side to the silicon wafer side. Since the tunnel barriers of silicon nitride and silicon oxynitride are relatively low, the thickness of the passivated tunnel layer can be appropriately widened on the premise of ensuring the tunnel efficiency, thus, the holes of the passivated tunnel layer are favorably reduced, the generation and combination rate of current leakage are reduced, the process window is expanded, and the process stability is improved.

Description

technical field [0001] The invention relates to the field of solar cells, in particular to a tunneling silicon-oxygen-nitride layer passivation contact solar cell and a preparation method thereof. Background technique [0002] Tunnel oxide passivated contact (TunnelOxidePassivatedContact, TOPCon) solar cell is a new type of silicon solar cell proposed by Fraunhofer Institute for Solar Energy Research in Germany in recent years. The battery uses an n-type silicon wafer, and the back of the silicon wafer is covered with a layer of silicon oxide layer below 2nm as a passivation tunneling layer, and then covered with a layer of doped thin-film silicon layer to passivate the back of the battery. The basic cell structure of the tunnel oxide passivation contact solar cell see figure 1 As shown, the back structure of the solar cell is an n-type silicon wafer, a passivation tunneling layer (silicon oxide layer), a doped n-type thin film silicon layer, and a metal electrode layer. W...

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Problems solved by technology

However, the silicon oxide layer also has disadvantages as a passivation tunneling layer. Due to the large forbidden band width of silicon oxide (about 8.9eV), the electron and hole transport barrier is relatively large, which is not conducive to the transmission of electrons or holes. Transport, when the thickness of the silicon oxide layer used as a tunneling oxide exceeds 2nm, its tunneling efficiency begins to drop significantly, which affects the fill factor. In order to enable electrons to tunnel through the silicon oxide layer as a passivation tunneling layer, it is necessary to The silicon layer is made very thin, usually controlled below 2nm, so holes are easy to form during the preparation process, resulting in increased leakage current, and in the subsequent high-temperature annealing process, atoms such as phosphorus in the doped thin-film silicon layer are easy to diffuse into as In the silicon oxide layer of the passivation tunneling layer, the integrity of the silicon oxide layer as the passivation tunneling layer is destroyed, resulting in increased leakage current and recombination; in addition, the thin silicon oxide layer has a low defect energy level density, with Positive charge density is low, and the field passivation effect on silicon wafers is weakened

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