Open-circuit voltage deficit, radiative sub-bandgap states, and prospects in quantum dot solar cells.
Quantum dot photovoltaics (QDPV) offer the potential for low-cost solar cells. To develop strategies for continued improvement in QDPVs, a better understanding of the factors that limit their performance is essential. Here, we study carrier recombination processes that limit the power conversion efficiency of PbS QDPVs. We demonstrate the presence of radiative sub-bandgap states and sub-bandgap state filling in operating devices by using photoluminescence (PL) and electroluminescence (EL) spectroscopy. These sub-bandgap states are most likely the origin of the high open-circuit-voltage (VOC) deficit and relatively limited carrier collection that have thus far been observed in QDPVs. Combining these results with our perspectives on recent progress in QDPV, we conclude that eliminating sub-bandgap states in PbS QD films has the potential to show a greater gain than may be attainable by optimization of interfaces between QDs and other materials. We suggest possible future directions that could guide the design of high-performance QDPVs.
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Chia-Hao Marcus
CH
Chuang
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Andrea
A
Maurano
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Riley E
RE
Brandt
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Gyu Weon
GW
Hwang
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Joel
J
Jean
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Tonio
T
Buonassisi
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Vladimir
V
Bulović
†Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Mechanical Engineering, and ∥Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Moungi G
MG
Bawendi
D011211:Electric Power Supplies; D006046:Gold / Q000737:chemistry; D007854:Lead / Q000737:chemistry*; D045663:Quantum Dots; D012993:Solar Energy; D013050:Spectrometry, Fluorescence; D013440:Sulfides / Q000737:chemistry*
D013440:Sulfides; C018391:lead sulfide; D007854:Lead; D006046:Gold
PbS; photovoltaics; quantum dot; solar energy; sub-bandgap state