Heavy-Metal-Free Flexible Hybrid Polymer-Nanocrystal Photodetectors Sensitive to 1.5 μm Wavelength

Abstract

Photodetection in the short-wave infrared (SWIR) wavelength window represents one of the core technologies allowing for many applications. Most current photodetectors suffer from high cost due to the epitaxial growth requirements and the ecological issue due to the use of highly toxic heavy-metal elements. Toward alternative SWIR photodetection strategies, in this work, high-performance heavy-metal-free flexible photodetectors sensitive to λ = 1.5 μm photons are presented based on the formation of a solution-processed hybrid composed of a conjugated diketopyrrolopyrrole-base polymer/PC70BM bulk heterojunction organic host together with inorganic guest NaYF4:15%Er3+ upconversion nanoparticles (UCNPs). Under the illumination of λ = 1.5 μm SWIR photons, optimized hybrid bulk-heterojunction (BHJ)/UCNP photodetectors exhibit a photoresponsivity of 0.73 and 0.44 mA/W, respectively, for devices built on rigid indium tin oxide (ITO)/glass and flexible ITO/polyethylene terephthalate substrates. These hybrid photodetectors are capable of performing SWIR photodetection with a fast operation speed, characterized by a short photocurrent rise time down to 80 μs, together with an excellent mechanical robustness for flexible applications. Exhibiting simultaneously multiple advantages including solution-processability, flexibility, and the absence of toxic heavy metal elements together with a fast operation speed and good photoresponsivity, these hybrid BHJ­(DPPTT-T/PC70BM)/UCNP photodetectors are promising candidates for next-generation low-cost and high-performance SWIR photodetectors.

Upconversion nanoparticles extending the spectral sensitivity of silicon photodetectors to λ = 1.5 μm

“…By comparison to the rise/fall time of the blank Si-PD which is 10 ns/10 ns, the photoresponse time of hybrid devices is longer, which is most likely limited by the fluorescence lifetime of the applied UCNPs (see Figure S6 of the supplementary material) and the coupling between the UCNPs and the Si device underneath. Overall, with a detectivity higher than the previous works employing erbium-doped silicate nanosheet/hybrid perovskite [22] and UCNP/conjugated polymer [28,29] and a photoresponse time comparable to, or shorter than previous works [22], the photodetection performance of the UCNP-Si hybrid PDs described here is highly encouraging. Here, different material systems possessing photodetection capability at λ = 1.5 µm are summarized in Table 1.…”

“…A hydrothermal route [29,30] was used for the synthesis of the Er 3+ -doped NaYF4 UCNPs in this work.…”

“…All measurements were performed at room temperature. The solution-processed colloidal Er 3+ -doped NaYF4 UCNPs were synthesized by a hydrothermal method according to a previously described protocol [29,30]. The UCNPs applied in this work have an average diameter of 450 nm (Figure 1(a)).…”

“…Solutionprocessed colloidal upconversion nanoparticles (UCNPs), typically doped by trivalent lanthanide cations, have also shown their high potential for such applications. Besides the fields of biomedical engineering [23][24][25] and solar energy harvesting [26,27], they have also been applied to photodetection [28,29]. Working on photodetectors sensitive to the wavelength of 1.5 µm, Zhao and co-workers recently fabricated flexible photoconductors by mixing Er 3+ -doped UCNPs with conjugated polymer [28].…”

Scalable Synthesis of a Sub-10 nm Chalcopyrite (CuFeS2) Nanocrystal by the Microwave-Assisted Synthesis Technique and Its Application in a Heavy-Metal-Free Broad-Band Photodetector

“… 7 − 10 Therefore, development of earth-abundant, nontoxic, and eco-friendly nanocrystal materials is of utmost importance. 11 − 13 Accordingly, a large variety of different heavy-metal-free nanocrystals have been developed including Cu 2 ZnSnS 4 (CZTS), 14 CuInS 2 (CIS), 9 , 14 CuInZnS (CIZS), 15 Cu 2 SnS 3 , 16 and CuFeS 2 . 17 Among them, chalcopyrite (CuFeS 2 ) is one of the important materials for both optoelectronic and biomedical applications.…”