Depleted-Heterojunction Colloidal Quantum Dot Solar Cells

Andras G. Pattantyus-Abraham, Illan J. Kramer, Aaron R. Barkhouse, Xihua Wang, Gerasimos Konstantatos, Ratan Debnath, Larissa Levina, Ines Raabe, Mohammad K. Nazeeruddin, Michael Grätzel, Edward H. Sargent

Research output: Contribution to journalArticlepeer-review

703 Scopus citations

Abstract

Colloidal quantum dot (CQD) photovoltaics combine low-cost solution processability with quantum size-effect tunability to match absorption with the solar spectrum. Rapid recent advances in CQD photovoltaics have led to impressive 3.6% AM1.5 solar power conversion efficiencies. Two distinct device architectures and operating mechanisms have been advanced. The first-the Schottky device-was optimized and explained in terms of a depletion region driving electron-hole pair separation on the semiconductor side of a junction between an opaque low-work-function metal and a p-type CQD film. The second-the excitonic device-employed a CQD layer atop a transparent conductive oxide (TCO) and was explained in terms of diffusive exciton transport via energy transfer followed by exciton separation at the type-II heterointerface between the CQD film and the TCO. Here we fabricate CQD photovoltaic devices on TCOs and show that our devices rely on the establishment of a depletion region for field-driven charge transport and separation, and that they also exploit the large bandgap of the TCO to improve rectification and block undesired hole extraction. The resultant depletedheterojunction solar cells provide a 5.1% AM1.5 power conversion efficiency. The devices employ infrared-bandgap size-effect-tuned PbS CQDs, enabling broadband harvesting of the solar spectrum. We report the highest opencircuit voltages observed in solid-state CQD solar cells to date, as well as fill factors approaching 60%, through the combination of efficient hole blocking (heterojunction) and very small minority carrier density (depletion) in the large-bandgap moiety. © 2010 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)3374-3380
Number of pages7
JournalACS Nano
Volume4
Issue number6
DOIs
StatePublished - May 24 2010
Externally publishedYes

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