High-Efficiency Air-Stable Colloidal Quantum Dot Solar Cells Based on a Potassium-Doped ZnO Electron-Accepting Layer

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Title
High-Efficiency Air-Stable Colloidal Quantum Dot Solar Cells Based on a Potassium-Doped ZnO Electron-Accepting Layer
Author
Azmi, RandiSeo, GabseokAhn, Tae KyuJang, Sung-Yeon
Issue Date
2018-10
Publisher
AMER CHEMICAL SOC
Citation
ACS APPLIED MATERIALS & INTERFACES, v.10, no.41, pp.35244 - 35249
Abstract
High-efficiency colloidal quantum dot (CQD) solar cells (CQDSCs) with improved air stability were developed by employing potassium-modified ZnO as an electron-accepting layer (EAL). The effective potassium modification was achievable by a simple treatment with a KOH solution of pristine ZnO films prepared by a low-temperature solution process. The resulting K-doped ZnO (ZnO-K) exhibited EAL properties superior to those of a pristine ZnO-EAL. The Fermi energy level of ZnO was upshifted, which increased the internal electric field and amplified the depletion region (i.e., charge drift) of the devices. The surface defects of ZnO were effectively passivated by K modification, which considerably suppressed interfacial charge recombination. The CQDSC based on ZnO-K achieved improved power conversion efficiency (PCE) of approximate to 10.75% (V-OC of 0.67 V, J(SC) of 23.89 mA cm(2), and fill factor of 0.68), whereas the CQDSC based on pristine ZnO showed PCE of 9.97%. Moreover, the suppressed surface defects of ZnO-K substantially improved long-term stability under air. The device using ZnO-K exhibited superior long-term air storage stability (96% retention after 90 days) compared to that using pristine ZnO (88% retention after 90 days). The ZnO-K-based device also exhibited improved photostability under air. Under continuous light illumination for 600 min, the ZnO-K-based device retained 96% of its initial PCE, whereas the pristine ZnO-based device retained only 67%.
URI
https://scholarworks.unist.ac.kr/handle/201301/26757
URL
https://pubs.acs.org/doi/10.1021/acsami.8b12577
DOI
10.1021/acsami.8b12577
ISSN
1944-8244
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