Activated Electron-Transport Layers for Infrared Quantum Dot Optoelectronics

Jongmin Choi, Jea Woong Jo, F. Pelayo García de Arquer, Yong Biao Zhao, Bin Sun, Junghwan Kim, Min Jae Choi, Se Woong Baek, Andrew H. Proppe, Ali Seifitokaldani, Dae Hyun Nam, Peicheng Li, Olivier Ouellette, Younghoon Kim, Oleksandr Voznyy, Sjoerd Hoogland, Shana O. Kelley, Zheng Hong Lu, Edward H. Sargent*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Photovoltaic (PV) materials such as perovskites and silicon are generally unabsorptive at wavelengths longer than 1100 nm, leaving a significant portion of the IR solar spectrum unharvested. Small-bandgap colloidal quantum dots (CQDs) are a promising platform to offer tandem complementary IR PV solutions. Today, the best performing CQD PVs use zinc oxide (ZnO) as an electron-transport layer. However, these electrodes require ultraviolet (UV)-light activation to overcome the low carrier density of ZnO, precluding the realization of CQD tandem photovoltaics. Here, a new sol–gel UV-free electrode based on Al/Cl hybrid doping of ZnO (CAZO) is developed. Al heterovalent doping provides a strong n-type character while Cl surface passivation leads to a more favorable band alignment for electron extraction. CAZO CQD IR solar cell devices exhibit, at wavelengths beyond the Si bandgap, an external quantum efficiency of 73%, leading to an additional 0.92% IR power conversion efficiency without UV activation. Conventional ZnO devices, on the other hand, add fewer than 0.01 power points at these operating conditions.

Original languageEnglish (US)
Article number1801720
JournalAdvanced Materials
Issue number29
StatePublished - Jul 19 2018


  • Infrared
  • ZnO
  • conductivity
  • doping
  • quantum dot solar cells

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering


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