Extremely low surface recombination in 1 Ω cm n‐type monocrystalline silicon

Christian Reichel,Ruy S Bonilla,Martin Hermle,Peter R Wilshaw

doi:10.1002/pssr.201600307

Abstract

A key requirement in the recent development of highly efficient silicon solar cells is the outstanding passivation of their surfaces. In this work, plasma enhanced chemical vapour deposition of a triple layer dielectric consisting of amorphous silicon, silicon oxide and silicon nitride, charged extrinsically using corona, has been used to demonstrate extremely low surface recombination. Assuming Richter's parametrisation for bulk lifetime, an effective surface recombination velocity Seff = 0.1 cm/s at Δn = 1015 cm–3 has been obtained for planar, float zone, n ‐type, 1 Ω cm silicon. This equates to a saturation current density J0s = 0.3 fA/cm2, and a 1‐sun implied open‐circuit voltage of 738 mV. These surface recombination parameters are among the lowest reported for 1 Ω cm c‐Si. A combination of impedance spectroscopy and corona‐lifetime measurements shows that the outstanding chemical passivation is due to the small hole capture cross section for states at the interface between the Si and a‐Si layer which are hydrogenated during nitride deposition. (© 2016 The Authors. Phys. Status Solidi RRL published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Highlights

Recombination of photo-generated carriers at surfaces and interfaces in optoelectronic devices imposes a major limit to their performance
3 Results and discussion The chemical and field effect components of passivation in the amorphous silicon (a-Si)/silicon oxide (SiOx)/SiNx stack were studied by producing specimens without the SiOx and/or the SiNx layers
Possible that the trap states sampled using the CGV method are at the aSi/SiOx interface, or even in the a-Si bulk

Summary

Introduction

Recombination of photo-generated carriers at surfaces and interfaces in optoelectronic devices imposes a major limit to their performance Minimizing such recombination, known as passivation, has become a major topic of study as more efficient devices are required. A surface passivation technique must endure the operating conditions of the device for a length of time as long as that of the device itself This may require dielectric materials with stable charge over 25 years, known as electrets [10]. In the recent years has the stability issue being tackled with some success [11] When solved, such electret films may become an essential part in the surface passivation of optoelectronic devices. A triple layer dielectric film deposited at temperatures below 250 °C has been charged extrinsically using corona discharge to demonstrate outstanding surface passivation of 1 Ω cm n-type c-Si

Methods

Results and discussion

Conclusions