Solution-Processed Sintered Nanocrystal Solar Cells via Layer-by-Layer Assembly

• Published in: Nano letters 2011-07, Vol.11 (7), p.2856-2864
• Main Authors: Jasieniak, Jacek, MacDonald, Brandon I, Watkins, Scott E, Mulvaney, Paul
• Format: Article
• Language: English
• Subjects: Applied sciences; Cadmium Compounds - chemistry; Cadmium tellurides; Cross-disciplinary physics: materials science; rheology; Crystallites; Electric Power Supplies; Energy; Exact sciences and technology; Heat treatment; Materials science; Membranes, Artificial; Methods of nanofabrication; Nanocrystalline materials; Nanocrystals; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nanostructures - chemistry; Nanotechnology; Natural energy; Particle Size; Photovoltaic cells; Photovoltaic conversion; Physics; Semiconductors; Solar cells; Solar cells. Photoelectrochemical cells; Solar Energy; Solutions; Surface Properties; Tellurium - chemistry; Temperature; Vacuum; Zinc Oxide - chemistry
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl201282v

Solar cells made by high temperature and vacuum processes from inorganic semiconductors are at a perceived cost disadvantage when compared with solution-processed systems such as organic and dye-sensitized solar cells. We demonstrate that totally solution processable solar cells can be fabricated from inorganic nanocrystal inks in air at temperature as low as 300 °C. Focusing on a CdTe/ZnO thin-film system, we report solar cells that achieve power conversion efficiencies of 6.9% with greater than 90% internal quantum efficiency. In our approach, nanocrystals are deposited from solution in a layer-by-layer process. Chemical and thermal treatments between layers induce large scale grain formation, turning the 4 nm CdTe particles into pinhole-free films with an optimized average crystallite size of ∼70 nm. Through capacitance–voltage measurements we demonstrate that the CdTe layer is fully depleted which enables the charge carrier collection to be maximized.