title: Enhanced open-circuit voltage of PbS nanocrystal quantum dot solar cells.
abstract: Nanocrystal quantum dots (QD) show great promise toward improving solar cell efficiencies through the use of quantum confinement to tune absorbance across the solar spectrum and enable multi-exciton generation. Despite this remarkable potential for high photocurrent generation, the achievable open-circuit voltage (Voc) is fundamentally limited due to non-radiative recombination processes in QD solar cells. Here we report the highest open-circuit voltages to date for colloidal QD based solar cells under one sun illumination. This Voc of 692 ± 7 mV for 1.4 eV PbS QDs is a result of improved passivation of the defective QD surface, demonstrating Voc(mV)=553Eg/q-59 as a function of the QD bandgap (Eg). Comparing experimental Voc variation with the theoretical upper-limit obtained from one diode modeling of the cells with different Eg, these results clearly demonstrate that there is a tremendous opportunity for improvement of Voc to values greater than 1 V by using smaller QDs in QD solar cells.
authors.affiliation: U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, United States. woojun.yoon@ieee.org
authors.forename: Woojun
authors.initials: W
authors.lastname: Yoon
authors.forename: Janice E
authors.initials: JE
authors.lastname: Boercker
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Lumb
authors.forename: Diogenes
authors.initials: D
authors.lastname: Placencia
authors.forename: Edward E
authors.initials: EE
authors.lastname: Foos
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Tischler
mesh_terms: D011211:Electric Power Supplies; D007854:Lead / Q000737:chemistry; D045663:Quantum Dots / Q000737:chemistry*; D012993:Solar Energy; D013440:Sulfides / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D013440:Sulfides; C018391:lead sulfide; D007854:Lead