A Facet‐Specific Quantum Dot Passivation Strategy for Colloid Management and Efficient Infrared Photovoltaics

作者：Younghoon Kim, Fanglin Che, Jea Woong Jo, Jongmin Choi, Francisco Pelayo García de Arquer, Oleksandr Voznyy, Bin Xiang Sun, Junghwan Kim, Min‐Jae Choi, Rafael Quintero‐Bermudez, Fengjia Fan, Chih‐Shan Tan, Eva Bladt, Grant Walters, Andrew H. Proppe, Chengqin Zou, Haifeng Yuan, Sara Bals, Johan Hofkens, Maarten B. J. Roeffaers, Sjoerd Hoogland, Edward Hartley Sargent · 发表于：Advanced Materials · 年份：2019 · DOI：10.1002/adma.201805580 · 被引用次数：141 · 研究领域：Quantum Dots Synthesis And Properties、Chalcogenide Semiconductor Thin Films、Perovskite Materials and Applications

Colloidal nanocrystals combine size- and facet-dependent properties with solution processing. They offer thus a compelling suite of materials for technological applications. Their size- and facet-tunable features are studied in synthesis; however, to exploit their features in optoelectronic devices, it will be essential to translate control over size and facets from the colloid all the way to the film. Larger-diameter colloidal quantum dots (CQDs) offer the attractive possibility of harvesting infrared (IR) solar energy beyond absorption of silicon photovoltaics. These CQDs exhibit facets (nonpolar (100)) undisplayed in small-diameter CQDs; and the materials chemistry of smaller nanocrystals fails consequently to translate to materials for the short-wavelength IR regime. A new colloidal management strategy targeting the passivation of both (100) and (111) facets is demonstrated using distinct choices of cations and anions. The approach leads to narrow-bandgap CQDs with impressive colloidal stability and photoluminescence quantum yield. Photophysical studies confirm a reduction both in Stokes shift (≈47 meV) and Urbach tail (≈29 meV). This approach provides a ≈50% increase in the power conversion efficiency of IR photovoltaics compared to controls, and a ≈70% external quantum efficiency at their excitonic peak.