Nanocrystalline thin film silicon solar cells: A deeper look into p/i interface formation

Andriy Lyubchyk, Sergej Alexandrovich Filonovich, Tiago Mateus, Manuel João Mendes, António Vicente, Joaquim Pratas Leitão, Bruno Poças Falcão, Elvira Fortunato, Hugo Águas, Rodrigo Martins

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The p/i interface plays a major role in the conversion efficiency of nanocrystalline silicon (nc-Si:H) solar cells. Under plasma-enhanced chemical vapor deposition (PECVD) of the intrinsic (i) nc-Si:H layer, ion bombardment can severely affect the underlying p-doped layer and degrade the solar cell performance. The core of the present work is to investigate the effect of light and heavy ion bombardment on the structural modifications of the p-layer during the p/i interface formation. The properties of the nc-Si:H materials deposited under distinct conditions are analyzed and correlated to the deposition rate and the resulting cell efficiency. To recreate the ion bombardment during the initial stages of the i-layer deposition on the p-layer, hydrogen plasma treatment was performed for 30 s (light ion bombardment), after which a flux of silane was introduced into the deposition chamber in order to initiate the heavy ion bombardment and growth of an ultra-thin (5 nm) i-layer. The structural changes of the p-type nc-Si:H layers were observed by spectroscopic ellipsometry. The obtained results confirm that detrimental structural modifications (e.g. partial amorphization of the sub-surface region and bulk) occur in the p-layer, caused by the ion bombardment. To minimize this effect, a protective buffer layer is investigated able to improve the performance of the solar cells fabricated under increased growth rate conditions.

Original languageEnglish
Pages (from-to)25-31
Number of pages7
JournalTHIN SOLID FILMS
Volume591
Issue numberPart A
DOIs
Publication statusPublished - 30 Sep 2015

Keywords

  • Buffer layer
  • Ion bombardment
  • Nanocrystalline silicon
  • p/i interface
  • Thin film solar cells

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