Simulation and Fabrication of HfO2 Thin Films Passivating Si from a Numerical Computer and Remote Plasma ALD

Xiao-Ying Zhang,Xu-Yang Zou,Chia-Hsun Hsu,Lin-Gui Xie,Wen-Zhang Zhu,Si-Xin Huang,Wei Huang,Song-Yan Chen,Shui-Yang Lien,Lian-Dong Chen,Yun-Shao Cho

doi:10.3390/app7121244

Abstract

Recombination of charge carriers at silicon surfaces is one of the biggest loss mechanisms in crystalline silicon (c-Si) solar cells. Hafnium oxide (HfO2) has attracted much attention as a passivation layer for n-type c-Si because of its positive fixed charges and thermal stability. In this study, HfO2 films are deposited on n-type c-Si using remote plasma atomic layer deposition (RP-ALD). Post-annealing is performed using a rapid thermal processing system at different temperatures in nitrogen ambient for 10 min. The effects of post-annealing temperature on the passivation properties of the HfO2 films on c-Si are investigated. Personal computer one dimension numerical simulation for the passivated emitter and rear contact (PERC) solar cells with the HfO2 passivation layer is also presented. By means of modeling and numerical computer simulation, the influence of different front surface recombination velocity (SRV) and rear SRV on n-type silicon solar cell performance was investigated. Simulation results show that the n-type PERC solar cell with HfO2 single layer can have a conversion efficiency of 22.1%. The PERC using silicon nitride/HfO2 stacked passivation layer can further increase efficiency to 23.02% with an open-circuit voltage of 689 mV.

Highlights

Reduction of surface recombination is very important for crystalline silicon (c-Si)-based electronic devices, and especially for high-efficiency c-Si solar cells
The post-deposition rapid thermal anneal was performed in N2 for 10 min, and the annealing temperature was varied from 400 to 650 ◦ C to investigate the effect on surface passivation
The absorbance peaks at 415, 512, 600, 623, and 750 cm−1 are assigned to temperatures

Summary

Introduction

Reduction of surface recombination is very important for crystalline silicon (c-Si)-based electronic devices, and especially for high-efficiency c-Si solar cells. Conventional surface passivation for Si involves the formation of a thin silicon dioxide (SiO2 ) layer. This process requires a long period at high temperatures, leading to an increased thermal budget. Due to these process-related issues, low-temperature surface passivation methods for both heavily doped and moderately doped c-Si surfaces have been widely studied. HfO2 films have positive fixed charges and this makes it very suitable for passivation of n-type silicon wafers. The surface passivation properties of the HfO2 films deposited by a remote plasma atomic layer deposition system (RP-ALD) on n-type c-Si with different post-annealing temperatures are investigated. PC1D (Version 5.9, University of New South Wales, Sydney, NSW, Australia, 2003) simulation for HfO2 -passivated n-type silicon solar cells is presented

Experimental

Discussion

BaseBase contact

Photovoltaic

Conclusions