Morphological–Electrical Property Relation in Cu(In,Ga)(S,Se)2 Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment

Joo Hyun Kim, Min Kyu Kim, Abay Gadisa, Samuel J. Stuard, Masrur Morshed Nahid, Soyeong Kwon, Soohyun Bae, Byoungwoo Kim, Gi Soon Park, Da Hye Won, Dong Ki Lee, Dong Wook Kim, Tae Joo Shin, Young Rag Do, Jihyun Kim, Won Jun Choi, Harald Ade, Byoung Koun Min

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Solution-processed Cu(In,Ga)(S,Se)2 (CIGS) has a great potential for the production of large-area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum-processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution-processed CIGS solar cells.

Original languageEnglish
Article number2003865
Issue number48
Publication statusPublished - 2020 Dec 3


  • CIGS solar cell
  • average domain spacing
  • band grading
  • electron diffusion length
  • solution process

ASJC Scopus subject areas

  • Biotechnology
  • Biomaterials
  • Chemistry(all)
  • Materials Science(all)


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