Efficient solution-processed infrared photovoltaic cells: Planarized all-inorganic bulk heterojunction devices via inter-quantum-dot bridging during growth from solution

Abstract

Solution-processed thin-film organic, inorganic, and hybrid photovoltaic devices have achieved power conversion efficiencies as high as 5%. However, these devices remain limited by their capture of visible energy; more than a half of the sun's power lies in the infrared. Herein the authors demonstrate photovoltaic devices effective across the visible and all the way out to 1700 nm. Only through the use of ethanedithiol as a bridging molecule to affect interparticle linking were they able to achieve fabrication of smooth, continuous quantum dot films on rough, high-surface area transparent metal oxides. This allowed them to increase light absorption while maintaining efficient charge separation and extraction and at the same time avoiding electrical short circuits. They obtained monochromatic infrared power conversion efficiencies of 1.3%, a 50-fold gain over the previous published record of 0.025% in IR solution-processed photovoltaics. The authors demonstrate quantum size-effect tuning of device band gaps relevant to multijunction solar cells.

Solar Cells, Photodetectors, and Optical Sources from Infrared Colloidal Quantum Dots

“…[14,16] The premise of this approach was to create a charge-separating (type-II) heterojunction to enable rapid dissociation of excitons into separated electrons and holes for independent transport to their respective contacts. [17,18] Recent work [13] has instead employed a single phase of light-absorbing material -a colloidal quantum dot solid -in which excitons are created, and charges travel within the same phase to their respective contacts. [19] A Schottky barrier [20] was formed at the interface between a low-work-function metal contact (Al) and the p-type quantum dot solid.…”

Smooth‐Morphology Ultrasensitive Solution‐Processed Photodetectors

“…This film contraction leads to film cracking-often on multiple length scales ranging from nanometers to micrometers-that renders the resultant film unacceptable for applications demanding exceptional uniformity. [1,7,8] Here, we demonstrate for the first time that useful levels of photoconductive gain and excellent morphology are not mutually exclusive. Solution-phase ligand exchange is the key to this achievement.…”

Hybrid Polyfluorene-Based Optoelectronic Devices

“…More recently, the self-assembly of lead-salt nanocrystals into more complex nanowire (1D) (Cho et al, 2005;Jang et al, 2010;Koh et al, 2010), monolayer (2D) (Anikeeva et al, 2007(Anikeeva et al, , 2008Coe-Sullivan et al, 2003;Konstantatos et al, 2005;Steckel et al, 2003; and nanocrystalline films and superlattices structures (3D) (Hanrath et al, 2009;Klem et al, 2007Klem et al, , 2008Luther et al, 2008;Talapin et al, 2005) with a wide range of most promising optoelectronic properties has rapidly become a very active field of research, largely due to its facile solution-based processing. Recently, exciting reports such as the observation of superb multiple-exciton generation efficiencies (Sargent, 2009;Sukhovatkin et al, 2009), highly-efficient hot-electron injection (Tisdale et al, 2010), and cold-exciton recycling (Klar et al, 2009), have propelled nanocrystalline lead-chalcogenide film structures to the forefront of cutting-edge research (M. S. Kang et al, 2009;W.…”