Suppression of hydroxylation on the surface of colloidal quantum dots to enhance the open-circuit voltage of photovoltaics

The fine control over the surface of lead sulfide colloidal quantum dots (PbS CQDs) is increasingly important to achieve enhanced device performance. In particular, the in-gap trap state resulting from the surface hydroxylation of PbS CQDs is considered detrimental to photovoltaic performance. In th...

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Bibliographic Details
Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-01, Vol.8 (9), p.4844-4849
Main Authors: Song, Jung Hoon, Kim, Taewan, Park, Taiho, Jeong, Sohee
Format: Article
Language:English
Subjects:
Energy conversion efficiency
Fabrication
Hydroxylation
Lead sulfides
Ligands
Open circuit voltage
Optical analysis
Photoelectric effect
Photoelectric emission
Photovoltaic cells
Photovoltaics
Purification
Quantum dots
Solar cells
Sulfide
Surface analysis (chemical)
Synthesis
Transient photovoltage
Voltage
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Summary:The fine control over the surface of lead sulfide colloidal quantum dots (PbS CQDs) is increasingly important to achieve enhanced device performance. In particular, the in-gap trap state resulting from the surface hydroxylation of PbS CQDs is considered detrimental to photovoltaic performance. In this study, we developed a method to avoid hydroxyl formation on the PbS CQD surface by using an in situ solution-phase ligand-exchange process. The complete elimination of protic solvents and other hydroxyl sources from the CQD synthesis to device fabrication produced PbS CQD films without undesired hydroxyl ligands with a reduced trap density. In this process, the purification process, which accounts for nearly 60% of the synthesis cost, is completely excluded. The presence of trap states verified through optical analysis and the hydroxylation observed via surface analysis clearly agreed with the device characterization obtained by transient photovoltage and photocurrent. Consequently, the open-circuit voltage of the PbS CQD solar cells is improved by up to 10%, yielding a certified power-conversion efficiency of 11.6%. Suppression of hydroxylation on quantum dot surfaces demonstrated a solar cell efficiency of 11.6% with the synthesis cost down up to 59.3%.
ISSN:2050-7488
2050-7496
DOI:10.1039/c9ta12598a