Open-circuit voltage deficit, radiative sub-bandgap states, and prospects in quantum dot solar cells

Publication Type:

Journal Article

Source:

Nano Lett., ACS Publications, Volume 15, Issue 5, p.3286-3294 (2015)

ISBN:

1530-6984

Keywords:

2015, PbS, photovoltaics, quantum dot, solar energy, sub-bandgap state

Abstract:

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.