Journal
ACS NANO
Volume 16, Issue 1, Pages 1649-1660Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.1c10636
Keywords
Guanidinium; Pseudohalides; Perovskites; Colloidal Quantum Dots; Photovoltaics
Categories
Funding
- National Research Foundation of Korea (NRF) - Korea government (MIST) [NRF-2019R1F1A1045506, NRF-2021R1A2B5B01002879]
- Nano-Material Technology Development Program through the National Research Foundation of Korea (NRF) - Ministry of Science and ICT [NRF-02021M3H4A1A02049634]
- Institute of Information & Communications Technology Planning & Evaluation (IITP) - Korea government (MIST) [2020-0-01373]
- Hanyang University [HY202000000700019]
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This study achieves high-performance and stable CQDPVs by reconstructing the oxidized CQD surface with thiocyanate anions for better surface passivation and promoting the construction of epitaxial perovskite bridges within the CQD matrix using guanidinium cations. The photocurrents are over 30 mA cm(-2) with nearly 80% quantum efficiency at excitonic peaks, and stable operation is maintained under humid and ambient conditions, indicating interfacial recombination associated with band alignment governs both the CQDPV performance and stability.
Complete surface passivation of colloidal quantum dots (CQDs) and their strong electronic coupling are key factors toward high-performance CQD-based photovoltaics (CQDPVs). Also, the CQD matrices must be protected from oxidative environments, such as ambient air and moisture, to guarantee air-stable operation of the CQDPVs. Herein, we devise a complementary and effective approach to reconstruct the oxidized CQD surface using guanidinium and pseudohalide. Unlike conventional halides, thiocyanate anions provide better surface passivation with effective replacement of surface oxygen species and additional filling of defective sites, whereas guanidinium cations promote the construction of epitaxial perovskite bridges within the CQD matrix and augment electronic coupling. Additionally, we replace a defective 1,2-ethanedithiol-treated CQD hole transport layer (HTL) with robust polymeric HTLs, based on a judicious consideration of the energy level alignment established at the CQD/HTL interface. These efforts collectively result in high-performance and stable CQDPVs with photocurrents over 30 mA cm(-2), similar to 80% quantum efficiency at excitonic peaks and stable operation under humid and ambient conditions. Elucidation of carrier dynamics further reveals that interfacial recombination associated with band alignment governs both the CQDPV performance and stability.
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