Suppression of Thermally Induced Surface Traps in Colloidal Quantum Dot Solids via Ultrafast Pulsed Light

Eon Ji Lee; Wonjong Lee; Tae Ho Yun; Hyung Ryul You; Hae Jeong Kim; Han Na Yu; Soo Kwan Kim; Younghoon Kim; Hyungju Ahn; Jongchul Lim; Changyong Yim; Jongmin Choi

doi:10.1002/smll.202400380

Suppression of Thermally Induced Surface Traps in Colloidal Quantum Dot Solids via Ultrafast Pulsed Light

Eon Ji Lee, Wonjong Lee, Tae Ho Yun, Hyung Ryul You, Hae Jeong Kim, Han Na Yu, Soo Kwan Kim, Younghoon Kim, Hyungju Ahn, Jongchul Lim, Changyong Yim, Jongmin Choi

Research output: Contribution to journal › Article › peer-review

Abstract

Thermal annealing (TA) of colloidal quantum dot (CQD) films is considered an important process for recent high-performing CQD solar cells (SCs) due to its beneficial effects on CQD solids, including enhanced electrical conductivity, denser packing of CQD films, and the removal of organic residues and solvents. However, the conventional TA for CQDs, which requires several minutes, leads to hydroxylation and oxidation on the CQD surface, resulting in the formation of trap states and a subsequent decline in SC performance. To address these challenges, this study introduces a flashlight annealing (FLA) technique that significantly reduces the annealing time to the millisecond scale. Through the FLA approach, it successfully suppressed hydroxylation and oxidation, resulting in decreased trap states within the CQD solids while simultaneously preserving their charge transport properties. As a result, CQD SCs treated with FLA exhibited a notable improvement, achieving an open-circuit voltage of 0.66 V compared to 0.63 V in TA-treated devices, leading to an increase in power conversion efficiency from 12.71% to 13.50%.

Original language	English
Article number	2400380
Journal	Small
Volume	20
Issue number	36
DOIs	https://doi.org/10.1002/smll.202400380
State	Published - Sep 5 2024
Externally published	Yes

Funding

E.J. L. and W. L. contributed equally to this work. This research was supported by the National Research Council of Science & Technology (NST) grant by the Korea government (MSIT) (No. CAP 23070‐017). This work was also supported by the National Research Foundation (RS‐2023‐00223196) funded by the Korean government. C.Y. acknowledges funding from the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. NRF‐2021R1A5A8033165).

Funders	Funder number
National Research Council of Science and Technology
Ministry of Science, ICT and Future Planning	CAP 23070‐017
Ministry of Science, ICT and Future Planning
National Research Foundation of Korea	NRF‐2021R1A5A8033165, RS‐2023‐00223196
National Research Foundation of Korea

Keywords

PbS colloidal quantum dots
flashlight annealing
hydroxylation
oxidation
solar cells

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title = "Suppression of Thermally Induced Surface Traps in Colloidal Quantum Dot Solids via Ultrafast Pulsed Light",

abstract = "Thermal annealing (TA) of colloidal quantum dot (CQD) films is considered an important process for recent high-performing CQD solar cells (SCs) due to its beneficial effects on CQD solids, including enhanced electrical conductivity, denser packing of CQD films, and the removal of organic residues and solvents. However, the conventional TA for CQDs, which requires several minutes, leads to hydroxylation and oxidation on the CQD surface, resulting in the formation of trap states and a subsequent decline in SC performance. To address these challenges, this study introduces a flashlight annealing (FLA) technique that significantly reduces the annealing time to the millisecond scale. Through the FLA approach, it successfully suppressed hydroxylation and oxidation, resulting in decreased trap states within the CQD solids while simultaneously preserving their charge transport properties. As a result, CQD SCs treated with FLA exhibited a notable improvement, achieving an open-circuit voltage of 0.66 V compared to 0.63 V in TA-treated devices, leading to an increase in power conversion efficiency from 12.71% to 13.50%.",

keywords = "PbS colloidal quantum dots, flashlight annealing, hydroxylation, oxidation, solar cells",

author = "Lee, {Eon Ji} and Wonjong Lee and Yun, {Tae Ho} and You, {Hyung Ryul} and Kim, {Hae Jeong} and Yu, {Han Na} and Kim, {Soo Kwan} and Younghoon Kim and Hyungju Ahn and Jongchul Lim and Changyong Yim and Jongmin Choi",

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doi = "10.1002/smll.202400380",

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T1 - Suppression of Thermally Induced Surface Traps in Colloidal Quantum Dot Solids via Ultrafast Pulsed Light

AU - Lee, Eon Ji

AU - Lee, Wonjong

AU - Yun, Tae Ho

AU - You, Hyung Ryul

AU - Kim, Hae Jeong

AU - Yu, Han Na

AU - Kim, Soo Kwan

AU - Kim, Younghoon

AU - Ahn, Hyungju

AU - Lim, Jongchul

AU - Yim, Changyong

AU - Choi, Jongmin

PY - 2024/9/5

Y1 - 2024/9/5

N2 - Thermal annealing (TA) of colloidal quantum dot (CQD) films is considered an important process for recent high-performing CQD solar cells (SCs) due to its beneficial effects on CQD solids, including enhanced electrical conductivity, denser packing of CQD films, and the removal of organic residues and solvents. However, the conventional TA for CQDs, which requires several minutes, leads to hydroxylation and oxidation on the CQD surface, resulting in the formation of trap states and a subsequent decline in SC performance. To address these challenges, this study introduces a flashlight annealing (FLA) technique that significantly reduces the annealing time to the millisecond scale. Through the FLA approach, it successfully suppressed hydroxylation and oxidation, resulting in decreased trap states within the CQD solids while simultaneously preserving their charge transport properties. As a result, CQD SCs treated with FLA exhibited a notable improvement, achieving an open-circuit voltage of 0.66 V compared to 0.63 V in TA-treated devices, leading to an increase in power conversion efficiency from 12.71% to 13.50%.

AB - Thermal annealing (TA) of colloidal quantum dot (CQD) films is considered an important process for recent high-performing CQD solar cells (SCs) due to its beneficial effects on CQD solids, including enhanced electrical conductivity, denser packing of CQD films, and the removal of organic residues and solvents. However, the conventional TA for CQDs, which requires several minutes, leads to hydroxylation and oxidation on the CQD surface, resulting in the formation of trap states and a subsequent decline in SC performance. To address these challenges, this study introduces a flashlight annealing (FLA) technique that significantly reduces the annealing time to the millisecond scale. Through the FLA approach, it successfully suppressed hydroxylation and oxidation, resulting in decreased trap states within the CQD solids while simultaneously preserving their charge transport properties. As a result, CQD SCs treated with FLA exhibited a notable improvement, achieving an open-circuit voltage of 0.66 V compared to 0.63 V in TA-treated devices, leading to an increase in power conversion efficiency from 12.71% to 13.50%.

KW - PbS colloidal quantum dots

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KW - oxidation

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Suppression of Thermally Induced Surface Traps in Colloidal Quantum Dot Solids via Ultrafast Pulsed Light

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