Variations in Minority Carrier-Trapping Effects Caused by Hydrogen Passivation in Multicrystalline Silicon Wafer

Yujin Jung,Donghwan Kim,Yoonmook Kang,Hae-Seok Lee,Soohyun Bae,Kwan Hong Min

doi:10.3390/en13215783

Abstract

In a multicrystalline silicon (mc-Si) wafer, trapping effects frequently occur in the carrier lifetime measurement based on the quasi-steady-state photoconductance (QSSPC) technique. This affects the accurate measurement of the carrier lifetime of an mc-Si solar cell by causing distortions at a low injection level close to the Pmax point. Therefore, it is necessary to understand this effect and effectively minimize the trapping-center density. In this study, the variations in the minority carrier-trapping effect of hydrogen at different annealing temperatures in an mc-Si were observed using QSSPC, time-of-flight secondary ion mass spectroscopy, and atom probe tomography. A trapping effect was confirmed and occurred in the grain boundary area, and the effect was reduced by hydrogen. Thus, in an mc-Si wafer, effective hydrogen passivation on the grain area and grain boundary is crucial and was experimentally proven to minimize the distortion of the carrier lifetime.

Highlights

The effective carrier lifetime of a silicon wafer is an important parameter in evaluating the material performance of a crystalline silicon solar cell
~800 μm based on the Figure shows the results of the carrier lifetime structure prepared for the measurement of the minority carrier lifetime and the results of the grainmeasurement of the Al2 O3 /SiNx :H/multicrystalline silicon (mc-Si) wafer/SiNx :H/Al2 O3 samples by quasi-steady-state photoconductance (QSSPC) measurement at size measurement
There are changes noted in the carrier lifetime based on the annealing size of ~800 μm based on the electron-backscatter diffraction (EBSD) measurement

Summary

Introduction

The effective carrier lifetime of a silicon wafer is an important parameter in evaluating the material performance of a crystalline silicon solar cell. The injection level-dependent carrier lifetime measured using QSSPC is used to evaluate the emitter current densities [6,7] and surface and bulk recombination centers [8,9,10]. The QSSPC method is a very useful technique, it can yield inaccurate measurements due to the minority carrier-trapping centers. The bulk presence of trap centers can cause a relatively significant excess of the majority carrier, resulting in the distortion of photoconductance [8]. This carrier lifetime distortion occurs in a low injection level region close to the maximum power point of a solar cell, Energies 2020, 13, 5783; doi:10.3390/en13215783 www.mdpi.com/journal/energies

Methods

Results

Conclusion