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Article
Optimization of Open Circuit Voltage in Amorphous Silicon Solar Cells with Mixed-Phase (Amorphous + Nanocrystalline) p-Type Contacts of Low Nanocrystalline Content
Journal of Applied Physics (2007)
  • Joshua M. Pearce, Clarion University of Pennsylvania
  • N. Podzara, University of Toledo
  • R. W. Collins, University of Toledo
  • M. M. Al-Jassim
  • K. M. Jones
  • J. Deng, The Pennsylvania State University
  • C. R. Wronski, The Pennsylvania State University
Abstract
Both the origins of the high open circuit voltages (VOC) in amorphous siliconsolar cells having p layers prepared with very high hydrogen dilution and the physical structure of these optimum p layers remain poorly understood topics, with several studies offering conflicting views. This work attempts to overcome the limitations of previous studies by combining insights available from electronic measurements, real time spectroscopic ellipsometry, atomic force microscopy, and both high-resolution transmission electron microscopy(TEM) and dark field TEM of cross sections of entire solar cells. It is found that solar cells fabricated with p layers having a low volume fraction of nanocrystals embedded in a protocrystalline Si:H matrix possess lower recombination at the i∕p interface than standard cells and deliver a higher VOC. The growth of the p layers follows a thickness evolution in which pure protocrystalline character is observed at the interface to the i layer. However, a low density of nanocrystallites nucleates with increasing thickness. The advantages offered by the protocrystalline character associated with the amorphous phase of the mixed-phase (amorphous+nanocrystalline) p layers prepared with excess H2 dilution account for the improved VOC of the optimum p layers. In this model, the appearance of a low volume fraction of nanocrystals near the top transparent conductor interface is proposed to be incidental to the high VOC.
Disciplines
Publication Date
June 1, 2007
Publisher Statement
© 2007 American Institute of Physics. Publisher's PDF uploaded here in compliance with publisher policies. Publisher's version of record: http://dx.doi.org/10.1063/1.2714507
Citation Information
Joshua M. Pearce, N. Podzara, R. W. Collins, M. M. Al-Jassim, et al.. "Optimization of Open Circuit Voltage in Amorphous Silicon Solar Cells with Mixed-Phase (Amorphous + Nanocrystalline) p-Type Contacts of Low Nanocrystalline Content" Journal of Applied Physics Vol. 101 Iss. 11 (2007)
Available at: http://works.bepress.com/jmpearce/69/