Two-step photon absorption in InP/InGaP quantum dot solar cells

Hyun Kum, Yushuai Dai, Taketo Aihara, Michael A. Slocum, Takeshi Tayagaki, Anastasiia Fedorenko, Stephen J. Polly, Zachary Bittner, Takeyoshi Sugaya, Seth M. Hubbard

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Intermediate band solar cells promise improved efficiencies beyond the Shockley-Queisser limit by utilizing an intermediate band formed within the bandgap of a single junction solar cell. InP quantum dots (QDs) in an In0.49Ga0.51P host are a promising material system for this application, but two-step photon absorption has not yet been demonstrated. InP QDs were grown via metalorganic chemical vapor deposition, and a density, a diameter, and a height of 0.7 × 1010 cm−2, 56 ± 10 nm, and 18 ± 2.8 nm, respectively, were achieved. Time-resolved photoluminescence measurements show a long carrier lifetime of 240 ns, indicating a type-II band alignment of these InP quantum dots. Several n-i-p In0.49Ga0.51P solar cells were grown with both 3 and 5 layers of InP QDs in the i-region. While the solar cells showed an overall loss in short circuit current compared to reference cells due to emitter degradation, a sub-bandgap enhancement of 0.11 mA/cm2 was clearly observed, due to absorption and collection from the InP QDs. Finally, two-step photon absorption experiments have shown unambiguous photocurrent generation involving an intermediate band within the bandgap at temperatures up to 250 K.

Original languageEnglish
Article number043902
JournalApplied Physics Letters
Issue number4
Publication statusPublished - 2018 Jul 23

Bibliographical note

Funding Information:
The authors would like to acknowledge the U.S. Air Force Research Laboratory (Grant No. STTR FA9453-15-C-0404) for their support. The work in AIST was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry (METI).

Publisher Copyright:
© 2018 Author(s).

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)


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