Susanna M. Thon

Colloidal quantum dot research has led to significant advances in synthesis methods, in material and film processing techniques, and in characterization and optimization of optoelectronic properties. Studies of novel passivation strategies, including new or hybrid ligand systems, surface engineering, core/shell strategies, and self-healing surfaces, will reduce trap states, improve carrier transport, and reduce the extent of energy level pinning. Another route to improved electronic transport in quantum dot films will rely on densifying nanocrystal films through improved packing and, ideally ordering. Such films will eliminate diversity in path length and thus tortuosity in charge transport through the device. Significant studies have been performed on the electron-transporting component yet as the optoelectronic quality of the quantum dot solid improves, even greater enhancements will be required in both the electron- and hole-accepting layers to ensure optimal performance. Research will need to adjust existing systems or apply novel material solutions, while intensely studying the interfaces between the quantum dot film and electrodes to eliminate any potential losses. Finally, as single-junction quantum dot solar cells advance and improve, a renewed focus will be placed on multiple-junction integration, with the goal of creating high-efficiency devices through improved spectral utilization and minimal loss associated with photocarrier thermalization.

Air‐stable and soluble tetrabutylammonium fluoride (TBAF) is demonstrated as an efficient n‐type dopant for the conjugated polymer ClBDPPV. Electron transfer from F − anions to the π‐electron‐deficient ClBDPPV through anion–π electronic interactions is strongly corroborated by the combined results of electron spin resonance, UV–vis–NIR, and ultraviolet photoelectron spectroscopy. Doping of ClBDPPV with 25 mol% TBAF boosts electrical conductivity to up to 0.62 S cm −1 , among the highest conductivities that have been reported for solution‐processed n‐type conjugated polymers, with a thermoelectric power factor of 0.63 µW m −1 K −2 in air. Importantly, the Seebeck coefficient agrees with recently published correlations to conductivity. Moreover, the F − ‐doped ClBDPPV shows significant air stability, maintaining the conductivity of over 0.1 S cm −1 in a thick film after exposure to air for one week, to the best of our knowledge the first report of an air‐stable solution‐processable n‐doped conductive polymer with this level of conductivity. The result shows that using solution‐processable small‐anion salts such as TBAF as an n‐dopant of organic conjugated polymers possessing lower LUMO (lowest unoccupied molecular orbital), less than −4.2 eV) can open new opportunities toward high‐performance air‐stable solution‐processable n‐type thermoelectric (TE) conjugated polymers.

A colloidal quantum dot solar cell is fabricated by spray-coating under ambient conditions. By developing a room-temperature spray-coating technique and implementing a fully automated process with near monolayer control—an approach termed as sprayLD—an electronic defect is eliminated resulting in solar cell performance and statistical distribution superior to prior batch-processed methods along with a hero performance of 8.1%. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.