Enhanced Near-Infrared-to-Visible Upconversion by Synthetic Control of PbS Nanocrystal Triplet Photosensitizers

Abstract

Photon upconversion employing semiconductor nanocrystals (NCs) makes use of their large and tunable absorption to harvest light in the near-infrared (NIR) wavelengths as well as their small gap between singlet and triplet excited states to reduce energy losses. Here, we report the highest QY (11.8%) thus far for the conversion of NIR to yellow photons by improving the quality of the PbS NC. This high QY was achieved by using highly purified lead and thiourea precursors. This QY is 2.6 times higher than from NCs prepared with commercially available lead and sulfide precursors. Transient absorption spectroscopy reveals two reasons for the enhanced QY: longer intrinsic exciton lifetimes of PbS NCs and the ability to support a longer triplet lifetime for the surface-bound transmitter molecule. Overall, this results in a higher efficiency of triplet exciton transfer from the PbS NC light absorber to the emitter and thus a higher photon upconversion QY.

Photon Upconverting Solid Films with Improved Efficiency for Endowing Perovskite Solar Cells with Near‐Infrared Sensitivity

“…Much less or no energy loss in the ISC process was attained for semiconductor nanocrystals and osmium (Os) complexes with singlet-to-triplet (SÀ T) absorption. [23][24][25][26][27][28][29][30][31] Meanwhile, solid-state upconverters are desirable for device applications. The groups of Bulović, Bawendi, and Baldo achieved the NIR-to-vis TTA-UC in the solid-state.…”

Simultaneously High Upconversion Efficiency and Large Anti‐Stokes Shift by Using Os(II) Complex Dyad as Triplet Photosensitizer

“…[ 19–22 ] A creative strategy to improve the anti‐Stokes shift is to erase the energy loss of ISC by using the direct singlet‐to‐triplet (S‐T) transition absorption molecule as photosensitizers, and minimizing the energy loss of TTET by selecting the appropriate acceptors. [ 23–27 ]…”

Prospects of Coupled Organic–Inorganic Nanostructures for Charge and Energy Transfer Applications

“…Organic ligands and p-systems PbSe Rubrene [25] Pentacene [26] PbS 5,11-Bis(triethylsilylethynyl)anthradithiophene [27] Rubrene (acceptor) [28] , 5-carboxylic acid tetracene (transmitter) [29,30] Tetracene [31] 2-Carboxylic acid TIPS-tetracene [32] 2-Benzoic acid TIPS-pentacene [33] Zinc b-tetraaminophthalocyanine [13] Poly[sodium 2-(2-ethynyl-4-methoxyphenoxy)acetate] [34] CdSe Anthracene derivatives [35] Pentacene derivatives [36] Oligothiophenecarboxylic acid [37] 1-Perylenecarboxylic acid (PCA) [38] 2-Chloro-9,10-bisphenylethynylanthracene (acceptor), PCA (transmitter) [39] Diphenylanthracene (acceptor), bis(pyridine) anthracene (transmitter) [40] Diphenylanthracene (acceptor), 9-anthracene carboxylic acid (transmitter) [41,42] Zinc b-tetraaminophthalocyanine [43] CsPbBr 3 PCA [44] 1-Naphthalenecarboxylic acid [45] Diphenylanthracene (acceptor), aminodiphenylanthracene (transmitter) [46] Two-dimensional MoS 2 Methyl orange, rhodamine 6G, methylene blue [47] Zinc phthalocyanine [48] Pentacene [49] To prevent surface reconstruction, the manifestation of defects and a deterioration of the electronic properties discussed above, the surfaces of QDs need to be passivated by some matrix. [52] In epitaxially grown QDs, this is achieved by embedding the QDs in another inorganic material with matching lattice constant.…”