Single-step colloidal quantum dot films for infrared solar harvesting

• Published in: Applied physics letters Vol. 109; no. 18
• Main Authors: Kiani, Amirreza, Sutherland, Brandon R., Kim, Younghoon, Ouellette, Olivier, Levina, Larissa, Walters, Grant, Dinh, Cao-Thang, Liu, Mengxia, Voznyy, Oleksandr, Lan, Xinzheng, Labelle, Andre J., Ip, Alexander H., Proppe, Andrew, Ahmed, Ghada H., Mohammed, Omar F., Hoogland, Sjoerd, Sargent, Edward H.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 31-10-2016
• Subjects: Applied physics; Energy conversion efficiency; Energy gap; Harvesting; Infrared radiation; Light; Photovoltaic cells; Quantum dots; Silicon; Silicon wafers; Size effects; Solar cells
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4966217

Semiconductors with bandgaps in the near- to mid-infrared can harvest solar light that is otherwise wasted by conventional single-junction solar cell architectures. In particular, colloidal quantum dots (CQDs) are promising materials since they are cost-effective, processed from solution, and have a bandgap that can be tuned into the infrared (IR) via the quantum size effect. These characteristics enable them to harvest the infrared portion of the solar spectrum to which silicon is transparent. To date, IR CQD solar cells have been made using a wasteful and complex sequential layer-by-layer process. Here, we demonstrate ∼1 eV bandgap solar-harvesting CQD films deposited in a single step. By engineering a fast-drying solvent mixture for metal iodide-capped CQDs, we deposited active layers greater than 200 nm in thickness having a mean roughness less than 1 nm. We integrated these films into infrared solar cells that are stable in air and exhibit power conversion efficiencies of 3.5% under illumination by the full solar spectrum, and 0.4% through a simulated silicon solar cell filter.