TY - JOUR
T1 - Quantitative Electrochemical Control over Optical Gain in Quantum-Dot Solids
AU - Geuchies, Jaco J.
AU - Brynjarsson, Baldur
AU - Grimaldi, Gianluca
AU - Gudjonsdottir, Solrun
AU - Van Der Stam, Ward
AU - Evers, Wiel H.
AU - Houtepen, Arjan J.
PY - 2020
Y1 - 2020
N2 - Solution-processed quantum dot (QD) lasers are one of the holy grails of nanoscience. They are not yet commercialized because the lasing threshold is too high: one needs >1 exciton per QD, which is difficult to achieve because of fast nonradiative Auger recombination. The threshold can, however, be reduced by electronic doping of the QDs, which decreases the absorption near the band-edge, such that the stimulated emission (SE) can easily outcompete absorption. Here, we show that by electrochemically doping films of CdSe/CdS/ZnS QDs, we achieve quantitative control over the gain threshold. We obtain stable and reversible doping of more than two electrons per QD. We quantify the gain threshold and the charge carrier dynamics using ultrafast spectroelectrochemistry and achieve quantitative agreement between experiments and theory, including a vanishingly low gain threshold for doubly doped QDs. Over a range of wavelengths with appreciable gain coefficients, the gain thresholds reach record-low values of ∼1 × 10-5 excitons per QD. These results demonstrate a high level of control over the gain threshold in doped QD solids, opening a new route for the creation of cheap, solution-processable, low-threshold QD lasers.
AB - Solution-processed quantum dot (QD) lasers are one of the holy grails of nanoscience. They are not yet commercialized because the lasing threshold is too high: one needs >1 exciton per QD, which is difficult to achieve because of fast nonradiative Auger recombination. The threshold can, however, be reduced by electronic doping of the QDs, which decreases the absorption near the band-edge, such that the stimulated emission (SE) can easily outcompete absorption. Here, we show that by electrochemically doping films of CdSe/CdS/ZnS QDs, we achieve quantitative control over the gain threshold. We obtain stable and reversible doping of more than two electrons per QD. We quantify the gain threshold and the charge carrier dynamics using ultrafast spectroelectrochemistry and achieve quantitative agreement between experiments and theory, including a vanishingly low gain threshold for doubly doped QDs. Over a range of wavelengths with appreciable gain coefficients, the gain thresholds reach record-low values of ∼1 × 10-5 excitons per QD. These results demonstrate a high level of control over the gain threshold in doped QD solids, opening a new route for the creation of cheap, solution-processable, low-threshold QD lasers.
KW - doping
KW - electrochemistry
KW - optical gain
KW - quantum-dots
KW - transient absorption spectroscopy
KW - ultrafast spectroelectrochemistry
UR - http://www.scopus.com/inward/record.url?scp=85096715617&partnerID=8YFLogxK
U2 - 10.1021/acsnano.0c07365
DO - 10.1021/acsnano.0c07365
M3 - Article
AN - SCOPUS:85096715617
SN - 1936-0851
VL - 15
SP - 377
EP - 386
JO - ACS Nano
JF - ACS Nano
IS - 1
ER -