Two-step photon absorption in InP/InGaP quantum dot solar cells
Abstract
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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 23, 2018
- Source ID
- 10.1063/1.5037238
Entities
People
- Anastasiia Fedorenko
- Hyun S Kum
- Michael A. Slocum
- Seth M Hubbard
- Stephen Polly
- Takeshi Tayagaki
- Taketo Aihara
- Takeyoshi Sugaya
- Yushuai Dai
- Zachary S. Bittner
Organizations
- Air Force Research Laboratory
- National Institute of Advanced Industrial Science and Technology
- New Energy and Industrial Technology Development Organization
- Rochester Institute of Technology