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Influence of boron clustering on the emitter quality of implanted silicon solar cells: an atom probe tomography study
Author(s) -
Raghuwanshi Mohit,
Lanterne Adeline,
Le Perchec Jérôme,
Pareige Philippe,
Cadel Emmanuel,
Gall Samuel,
Duguay Sébastien
Publication year - 2015
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.2607
Subject(s) - atom probe , common emitter , wafer , ion implantation , boron , annealing (glass) , materials science , doping , silicon , saturation current , analytical chemistry (journal) , solar cell , thermal diffusivity , atom (system on chip) , nanometre , ion , optoelectronics , nanotechnology , chemistry , physics , organic chemistry , chromatography , quantum mechanics , voltage , transmission electron microscopy , computer science , composite material , embedded system
Abstract The use of ion implantation doping instead of the standard gaseous diffusion is a promising way to simplify the fabrication process of silicon solar cells. However, difficulties to form high‐quality boron (B) implanted emitters are encountered when implantation doses suitable for the emitter formation are used. This is due to a more or less complete activation of Boron after thermal annealing. To have a better insight into the actual state of the B distributions, we analyze three different B emitters prepared on textured Si wafers: (1) a BCl 3 diffused emitter and two B implanted emitters (fixed dose) annealed at (2) 950°C and at (3) 1050°C (less than an hour). Our investigations are in particular based on atom probe tomography, a technique able to explore 3D atomic distribution inside a material at nanometer scale. Atom probe tomography is employed here to characterize B atomic distribution inside textured Si solar cell emitters and to quantify clustering of B atoms. Here, we show that implanted emitters annealed at 950 °C present maximum clusters due to poor solubility at lower temperature and also highest emitter saturation current density (J 0e = 1000 fA/cm 2 ). Increasing the annealing temperature results in greatly improved J 0e (131 fA/cm 2 ) due to higher solubility and a consequently lower number of clusters. BCl 3 diffused emitters do not contain any B clusters and presented the best emitter quality. From our results, we conclude that clustering of B atoms is the main reason behind higher J 0e in the implanted boron emitters and hence degraded emitter quality. Copyright © 2015 John Wiley & Sons, Ltd.