Efficient solid-state infrared-to-visible photon upconversion on atomically thin monolayer semiconductors

Abstract

Upconverting infrared light into visible light via the triplet-triplet annihilation process in solid state is important for various applications including photovoltaics, photodetection, and bioimaging. Although inorganic semiconductors with broad absorption and negligible exchange energy loss have emerged as promising alternative to molecular sensitizers, currently, they have exclusively suffered from low efficiency and contained toxic elements in near-infrared (NIR)–to–visible upconversion. Here, we report an ultrathin bilayer film for NIR-to-visible upconversion based on atomically thin two-dimensional (2D) monolayer semiconductors. The atomic flatness and strong light absorption of 2D monolayer semiconductors enable ultrafast energy transfer and robust NIR-to-visible emission with a high upconversion quantum yield (1.1 ± 0.2%) at modest incident power (260 mW cm −2 ). Increasing layer thickness adversely quenches the upconversion emission, highlighting the 2D advantage. Considering the whole library of 2D semiconductors, the facile large-scale production and the ultrathin solid-state architecture open a new research field for solid-state upconversion applications.

Photon Upconversion in a Vapor Deposited 2D Inorganic–Organic Semiconductor Heterostructure

“…Exploiting solid-state triplet fusion upconversion (TUC) within hybrid TMD/organic semiconductor architectures has recently generated considerable interest among the optoelectronics community . During TUC, pairs of low-energy photons are converted into high-energy photons via an incoherent process mediated by the triplet (spin 1) excited states of organic semiconductors. , Since direct photoexcitation of these triplet states is spin-forbidden, TUC architectures employ triplet sensitizers that strongly absorb light and transfer photoexcitations to the molecular triplet acceptor states .…”

Triplet–triplet annihilation mediated photon upconversion solar energy systems

“…21,80,84 Most of the efficient NIR and Far-red sensitized TTA-UC systems have used rubrene as a key annihilator and dibenzotetraphenylperiflanthene (DBP) as a singlet acceptor/emitter. [85][86][87] Since rubrene satisfies the energetic condition for singlet fission i. e. 𝑆 1 (𝐸) ≥ 2𝑇 1 (𝐸), the upconverted singlet photon undergo singlet fission before emission, which reduces the overall 𝜙 𝑈𝐶 ∞ . DBP is used to avoid this loss channel via singlet energy transfer from rubrene to DBP because of its low-lying singlet state compared to rubrene (𝛥𝐸 𝑆 ≈ −0.14 eV).…”

“…85 Without DBP the best 𝜙 𝑈𝐶 = 3.65 % has been reported in Pdtetraphenyltetraanthroporphyrin (PdTPTAP)-rubrene emulsified mesoporous PVA films upon 810 nm excitation. 88 For red light sensitized TTA-UC, thermally evaporated rubrene on palladium phthalocyanine (PdPc) doped polystyrene surface (𝜙 𝑈𝐶 = 1.2 %) 47 and rubrene-DBP spin-coated on an atomically thin two-dimensional (2-D) layer of MoSe 2 as sensitizer (𝜙 𝑈𝐶 = 1.1 %) 87 were found to be the most efficient. Incidentally, most efficient solid-state TTA-UC system have been reported for Vis-to-Vis TTA-UC.…”

Role of Semiconductor Nanostructures in Photon Upconversion Applications

“…The organic sensitizers that do absorb in this region also tend to be less photostable and undergo rapid internal conversion to the ground state. , For this reason, coupling TTA upconverters to inorganic sensitizers that absorb in the red and NIR regions is a promising route to expand the spectral range of TTAs. In recent years, there have been many demonstrations of TTAs sensitized with a range of inorganic materials, including TMDs, bulk , and nanocrystalline − perovskites, and semiconductor quantum dots. ,,− For the purposes of this review, we will focus exclusively on examples using nanocrystalline materials.…”