Si-Doped Cu(In,Ga)Se2 Photovoltaic Devices with Energy Conversion Efficiencies Exceeding 16.5% without a Buffer Layer

Shogo Ishizuka, Jiro Nishinaga, Masayuki Iioka, Hirofumi Higuchi, Yukiko Kamikawa, Takashi Koida, Hajime Shibata, Paul Fons

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


In this communication, novel and simplified structure Cu(In,Ga)Se2 (CIGS) solar cells, which nominally consist of only a CIGS photoabsorber layer sandwiched between back and front contact layers but yet demonstrate high photovoltaic efficiencies, are reported. To realize this accomplishment, Si-doped CIGS films grown by the three-stage coevaporation method, B-doped ZnO transparent conductive oxide front contact layers deposited by chemical vapor deposition, and heat–light soaking treatments are used. Si-doping of CIGS films is found to modify the film surfaces and grain boundary properties and also affect the alkali metal distribution profiles in CIGS films. These effects are expected to contribute to improvements in buffer-free CIGS device performance. Heat–light soaking treatments, which are occasionally performed to improve conventional buffer-based CIGS device performance, are found to be also effective in enhancing buffer-free CIGS photovoltaic efficiencies. This result suggests that the mechanism behind the beneficial effects of heat–light soaking treatments originates from CIGS bulk issues and is independent of the buffer materials. Consequently, over 16.5% efficiencies, including an independently certified value, are demonstrated from completely buffer-free CIGS photovoltaic devices.

Original languageEnglish
Article number1702391
JournalAdvanced Energy Materials
Issue number11
Publication statusPublished - 2018 Apr 16
Externally publishedYes


  • Cu(In,Ga)Se
  • Si-doping
  • alkali metals
  • light-induced metastability
  • photovoltaics

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science


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