Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

• Year

  2020

• Author

  CEME

• Professor

  Prof. Jongmin Choi

• Journal

  Adv. Mater.(IF=27.398)

• Abstract

  Colloidal quantum dots (CQDs) are promising materials for photovoltaic (PV) applications owing to their size‐tunable bandgap and solution processing. However, reports on CQD PV stability have been limited so far to storage in the dark; or operation illuminated, but under an inert atmosphere. CQD PV devices that are stable under continuous operation in air have yet to be demonstrated—a limitation that is shown here to arise due to rapid oxidation of both CQDs and surface passivation. Here, a stable CQD PV device under continuous operation in air is demonstrated by introducing additional potassium iodide (KI) on the CQD surface that acts as a shielding layer and thus stands in the way of oxidation of the CQD surface. The devices (unencapsulated) retain >80% of their initial efficiency following 300 h of continuous operation in air, whereas CQD PV devices without KI lose the amount of performance within just 21 h. KI shielding also provides improved surface passivation and, as a result, a higher power conversion efficiency (PCE) of 12.6% compared with 11.4% for control devices.
  
  Prof. Jongmin Choi and his research group in the Department of Energy Science & Engineering at DGIST developed a stable colloidal quantum dot photovoltaics (CQD PV) device under continuous operation in air. The results were published in Advanced Materials (IF: 25.809, JCR 1.1%) on February 20, 2020.
  
  A stable CQD PV device under continuous operation in air is demonstrated by introducing additional potassium iodide (KI) on the CQD surface that acts as a shielding layer and thus stands in the way of oxidation of the CQD surface. The devices (unencapsulated) retain >80% of their initial efficiency following 300 h of continuous operation in air.
  
  This work provides insights into achieving stable CQDs for commercializing CQD optoelectronics.
  
  DGIST(총장 국양) 에너지공학전공 최종민 교수 연구팀은 토론토대학교 Edward H. Sargent 교수 연구팀과 협력하여 태양전지의 실제 구동환경에서 양자점 태양전지의 불안정성 원리에 대해 규명하고 이를 안정화 시킬 수 있는 리간드 교환 법을 개발하여, 2월 20일 에너지 재료 연구 분야의 저명한 국제학술지인 Advanced Materials (IF : 25.809, JCR 1.1%) 에 게재하였다
  
  새로 개발한 양자점 태양전지는 칼륨 (K)을 포함한 리간드 교환 법을 포함한 공정으로 제작하여, 표면 리간드를 산화로 부터 안정화 시키고 실제 태양전지의 구동조건 (Maximum Power Point in an Air Ambient)에서 300 시간동안 80% 이상의 초기 효율을 유지하는 소자를 구현하였다.
  
  양자점 태양전지의 안정성 저하 원인 규명 및 이를 극복할 수 있는 새로운 방법을 제안한 본 연구는 태양전지를 포함한 양자점을 기반 광전소자의 발전 및 상용화에 기여할 것으로 기대된다.