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Abstract
Large scale ordered Au nanoarrays are fabricated by nanosphere lithography technique. The photoluminescence improvement of CsPbBr3-xIx nanocrystals by more than three times is realized in the CsPbBr3-xIx nanocrystal/Au nanoarray/Si structure. Time-resolved photoluminescence decay curves indicate that the lifetime is decreased by introducing the Au nanoarrays, which results in a increasing radiation recombination rate. The reflection spectra with two major valleys (the dip in the curve) located at ∼325 nm and 545 nm of Au nanoarray/Si structure, which illustrates two plasmonic resonance absorption peaks of the Au nanoarrays. The enhancement of photoluminescence is ascribed to a well match between the excitation/emission of CsPbBr3-xIx nanocrystals and localized surface plasmon/gap plasmon resonance absorption of the ordered Au nanoarrays, as also revealed from the finite-difference time-domain simulation analysis. Our work offers an effective strategy to improve the fluorescence of perovskite nanocrystals and provide the potential for further applications.
© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
All-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) have attracted great attention in recent years due to their superior optoelectronic properties such as tunable emissions, narrow line widths, low exciton binding energies, high charge carrier mobility, and high photoluminescence quantum yields up to 90% [1–4]. CsPbX3 NCs not only have excellent optoelectronic properties but also have better stability, which makes a tremendous improvement in the performance of CsPbX3 NC-based devices, especially for light emitting diodes (LED) [5–6], solar cells [7–8]. Despite the great success, there is still substantial room for potential breakthroughs in CsPbX3 NC-based devices [9]. CsPbX3 NCs convert injected charge carriers into light and vice versa, for LED and solar cells, respectively. Thus, it is necessary to improve the photoluminescence (PL) intensity of the CsPbX3 NCs for further application.
Localized surface plasmon resonance (LSPR) has been proved to be an extremely effective mean for improving PL of NCs [10–14]. Not only the light absorption can be enhanced but also the radiative transition rate can be ameliorated, which is beneficial to improve the PL intensity. Qu and co-workers have reported that significant enhancement of the PL intensity of CsPbBr3@Ag hybrid nanocrystals was observed compared with that of pure CsPbBr3 nanocrystals, which can be attributed to the enhancement of absorbance by Ag induced plasmonic near-field effect [15]. Guo et al. have investigated the LSPR coupling behaviors of a radiating dipole with incorporating Au-Ag alloy nanoparticle in all-inorganic perovskite LED. An increase of 25% of the luminescence efficiency can be achieved [16]. Recently, our group introduced plasmonic Au nano-octahedrons into perovskite solar cell [17]. The power conversion efficiency of perovskite solar cell is increased from 16.95 to 19.05% with a short-circuit current density as high as 23.63 mA/cm2. It is attributed to LSPR based on Au nano-octahedrons, which enhanced light-trapping effect and photocarrier extraction. Additionally, metallic nanostructures with individual geometry and dimensions display unique LSPR. Therefore, it is important to design metallic nanostructures with different LSPR performance to meet the application of perovskite nanocrystals-based devices.
Additionally, PL emission can be tuned over the entire visible spectral region (410-700 nm) by adjusting the halide ratios in the CsPbX3 NCs solution via fast anion-exchange [18]. Emissions spectral region of CsPbX3 NCs are particular importance for their practical applications. For example, rose bengal (RB) with an absorption peak around 545 nm is an ideal photosensitizer to for photodynamic therapy [19]. It is of great significance to study the energy transfer between mixed halide perovskite CsPbBr3-xIx NCs and photosensitizers. Although there are still many problems such as moisture, heat, toxicity to be solved. The study of mixed halide perovskite CsPbBr3-xIx NCs with unique luminescence peak is great important to further application.
Here, we fabricated large scale ordered plasmonic Au nanoarrays (NAs) by nanosphere lithography technique. Mixed halide perovskite CsPbBr3-xIx NCs were obtained via fast anion-exchange. The LSPR/gap plasmon resonance absorption peaks are well match the excitation/emission of CsPbBr3-xIx NCs. More than three times enhancement of PL emission is realized in CsPbBr3-xIx NCs/Au NAs/Si structure.
2. Experimental section
2.1 Materials
Cs2CO3 (99.9%), Oleic acid (OA, 99.0%), 1-Octadecene (ODE, 90%), Oleylamine (OLA, 90%), PbBr2 (99.0%) were purchased from Aladdin (Shanghai, China). PbI2 (99.0%) was purchased from Advanced Election Technology Co., Ltd., China. Cyclohexane was purchased from Sinopharm Chemical Reagent Co., Ltd., China. Polystyrene (PS) spheres were purchased from Janus New-Materials Co., Ltd., China. All the chemicals were without purification.
2.2 Synthesis of CsPbX3 NCs
CsPbX3 NCs are synthesized by the hot injection method according to our previous works [20–21]. Preparation of Cs-oleate: Cs2CO3 (0.4 g), ODE (15 mL) and OA (1.25 mL) were loaded into 3-neck flask, dried for 1h under N2, and then heated to 150 °C until Cs2CO3 dissolved. Preparation of CsPbBr3 (or CsPbI3) QDs: PbBr2 (0.138 g) (or 0.173 g PbI2), ODE (10 mL), OLA (1 mL) and OA (1 mL) were loaded into a 3-neck flask, and then heated to 150 °C under N2. After complete dissolution of the PbBr2 (or PbI2) salt, the Cs-oleate solution (0.8 mL) prepared as described above was quickly injected. The reaction mixture was cooled by a quick ice-water bath. The CsPbBr3 (or CsPbI3) NCs were collected by centrifugation at 10000 rpm for 10 min, and then re-dispersed into 12 mL cyclohexane. By the control of halide ratios in the colloidal NCs, the mixture halide CsPbX3 NCs can be obtained [18,22]. Finally, 350 uL CsPbI3 and 2.5 mL CsPbBr3 NCs were added into the cuvette. The ratios (Br and I) given by stoichiometry of the halide CsPbX3 NC is 2.75:0.25. It is difficult to quantitatively determine iodine content due to their low concentration, thus the mixture halide CsPbX3 NCs products were denoted as “CsPbBr3-xIx” NCs.
2.3 Fabrication of Au NAs
Nanosphere lithography technique was used to fabricate the Au NAs through three primary steps, as illustrated schematically in Fig. 1. Firstly, a monolayer of PS nanospheres with diameter of 200 nm was coated on the p-type Si substrates by using the self-assembly technique, as described in our previous work [23–24]. Secondly, the Si substrates covered with monolayer PS nanospheres were treated by inductively coupled plasma (ICP) reactive ion etching system. The PS spheres’ diameter was decreased slightly by the ICP treatment and monolayer PS nanospheres with certain spaces were obtained. Au NAs with different ICP etching time have been fabricated in our work. Thirdly, an Au layer of ∼50 nm was deposited on the monolayer PS nanospheres to form Au NAs via vacuum thermal evaporation system. Finally, CsPbBr3-xIx NCs were spin-coated onto Au NAs/Si substrate at 2000 rpm for 20 s.
2.4 Characterization
The crystal structure of the sample was characterized by X-ray diffraction (XRD, SmartLab, Rigaku) with Cu Kα in 2θ-ω scan mode. The morphologies of CsPbX3 NCs were performed on transmission electron microscopy (TEM, JEM-2100PLUS). The SEM images were recorded on a field emission scanning electron microscope (FESEM, ZEISS Sigma 500). The UV-vis and reflection spectra were obtained by UV/VIS/NIR spectrophotometer (PerkinElmer, Lambda 1050). The steady-state PL spectra were tested by a fluorescent spectrometer (Edinburgh, FLS1000) with an excitation wavelength of 325 nm. Time-resolved photoluminescence (TRPL) spectra were collected by a 375 nm picosecond laser (EPL-375). Pulse width is a fixed value of 67.7 ps, while repetition rate is 20 MHz with a pulse period of 50 nanosecond.
3. Results and discussion
3.1 Characterization of CsPbBr3-xIx NCs
The XRD patterns of the as-obtained CsPbBr3-xIx NCs in Fig. 2(a) are consistent with the cubic perovskite CsPbBr3 (JCPDS 18-0364), which indicates the crystal structure of the CsPbBr3-xIx NCs will not be influenced by introduced a small number of CsPbI3 NCs to CsPbBr3 NCs as we described in the experimental section. As TEM images depict in inset of Fig. 2(a), the CsPbBr3-xIx NCs have cubic shapes with average sizes of ∼20 nm. The absorption spectra with an absorption edge at 538 nm, and strong PL emission at 541 nm under 325 nm excitation on Xenon lamp are presented in Fig. 2(b).
Fig. 2. (a) XRD patterns and TEM images (inset) of CsPbBr3-xIx NCs. (b) Optical absorption (left) and PL spectra (right) of CsPbBr3-xIx NCs under 325 nm excitation on Xenon lamp.
3.2 SEM of CsPbBr3-xIx NCs /Au NAs/Si
Figure 3(a) shows the SEM images of monolayer PS nanospheres on Si substrate. As SEM images depict, the PS nanospheres with the diameter of ∼200 nm are hexagonal closed-packed on the Si substrate. The morphologies of PS nanospheres on Si substrate after 120 s etched are shown in Fig. 3(b). Compared the original PS nanospheres, the diameter of these PS nanospheres decreases by ICP etching. After the ICP treatment, the diameter decreases from 200 to 140 nm. And the non-close-packed PS sphere template with 60 nm space was obtained. Figure 3(c) shows the morphology of Au film on the monolayer PS nanospheres maintains ordered NAs after Au deposition, which demonstrates the formation of periodic Au NAs structure. Noteworthy is that Au nanoparticles are agglomerated onto the PS nanospheres. Figure 3(d) presents SEM image of the cross section of CsPbBr3-xIx NCs/Au NAs/Si, CsPbBr3-xIx NCs are coated on the Au NAs/Si substrate.
Fig. 3. (a) SEM image of monolayer PS nanospheres on Si substrate. (b) SEM image of monolayer PS nanospheres etched 120 s by ICP on Si substrate. (c) SEM image of Au NAs/Si. (d) Cross-sectional SEM image of CsPbBr3-xIx NCs/Au NAs/Si.
3.3 PL and TRPL analysis
PL spectra of CsPbBr3-xIx NCs/Au NAs/Si under 325 nm excitation on Xenon lamp is shown in Fig. 4(a). The PL intensity of CsPbBr3-xIx NCs with Au NAs after 120 s ICP etched shows significant enhancement compared with that of pure CsPbBr3-xIx NCs on Si substrate, and the enhancement rate is determined to be more than three times. In Supplement 1, Fig. S1 illustrates the comparison of the emission spectra of Au NAs with different ICP etching time. The highest PL intensity can be obtained in CsPbBr3-xIx NCs/ICP 120 s Au NAs/Si structure. This enhancement can be attributed to the coupling of LSPR/gap plasmon resonance between the excitons in CsPbBr3-xIx NCs and charge density oscillations of Au NAs. Additionally, the PL peak of CsPbBr3-xIx NCs/Au NAs/Si with 541 nm is slightly blue-shifted by 10 nm compared to the reference, which is attributed to the interaction with LSPR [25–27]. Additionally, slight enhancement of PL emissions in CsPbBr3-xIx NCs/Au flat film/Si substrate can be found, which can be ascribed to the enhancement of absorption by reflecting the excitation light. To further confirm the incorporation of Au NAs increases the PL intensity of CsPbBr3-xIx NCs, the TRPL measurements are performed. Figure 4(b) shows the TRPL spectra of CsPbBr3-xIx NCs/Si, CsPbBr3-xIx NCs/Au flat film/Si and CsPbBr3-xIx NCs/Au NAs/Si, respectively. Compared to the CsPbBr3-xIx NCs without Au NAs or with Au flat film, the TRPL decayed fastest when Au NAs are incorporated. The biexponential TRPL decay curves can be fitted by the Eq. (1) [28]
Fig. 4. (a) PL spectra of CsPbBr3-xIx NCs/Si, CsPbBr3-xIx NCs/Au flat film/Si and CsPbBr3-xIx NCs/Au NAs/Si under 325 nm excitation on Xenon lamp, respectively. (b) TRPL spectra of CsPbBr3-xIx NCs/Si, CsPbBr3-xIx NCs/Au flat film/Si and CsPbBr3-xIx NCs/Au NAs/Si, respectively. Inset is table of the corresponding lifetimes.
3.4 Reflectance analysis
In order to further explain the luminescence enhancement, the reflection spectra of the Au NAs/Si, Au flat film/Si and flat Si wafer are measured, as shown in Fig. 5. The reflection spectra exhibit two major valley located at ∼325 nm and 545 nm, which indicates two plasmonic resonance absorption peaks of the Au NAs [31]. It should be noted that the PL emission peak of CsPbBr3-xIx NCs is around 541 nm, which has a good overlap with the LSPR/gap plasmon resonance peak of Au NAs, indicating that an effective resonance effect can be achieved between CsPbBr3-xIx NCs and Au NAs. Additionally, the excitation wavelength with 325 nm is well consistent with resonance absorption of Au NAs. It is believed that the existence of Au NAs can significantly enhance the excitation efficiency due to the coupling of plasmonic modes. Therefore, the mechanism for enhancing the fluorescence intensity of CsPbBr3-xIx NCs on Au NAs substrate is mainly assigned to improve their absorption ability for excitation light and radiative recombination rate of excitons. Moreover, reflection of Au flat film/Si is highest than that of Au NAs/Si and Si substrate. And slight enhancement of PL emissions in CsPbBr3-xIx NCs/Au flat film/Si substrate can be found in Fig. 4(a). Thus, the enhancement of PL emissions in Au flat film/Si substrate can be ascribed to the enhancement of absorption by reflecting the excitation light.
Fig. 5. Reflection spectra of Si, Au flat film/Si and Au NAs/Si (left); PL spectra of CsPbBr3-xIx NCs (right).
3.5 Numerical simulations
To further understand the enhancement of Au NAs, numerical electromagnetic simulations were carried out by the finite-difference time-domain method (FDTD Solutions 8.6.0, Lumerical Solutions). The electric field intensities of Au NAs under 325 nm and 545 nm incident light are calculated. Figure 6(a) and 6(b) present the local electric field intensity can be enhanced at surface of Au sphere. Moreover, the electric fields are strongly localized and enhanced in the interface between two Au spheres under 325 nm. Narrow gaps in subwavelength metal nanostructures are known to enhance the electric fields because the energy is confined in a small volume [32–33]. Therefore, the absorption of CsPbBr3-xIx NCs can be enhanced due to the LSPR/gap plasmon resonances of Au NAs. Additionally, strong gap plasmon resonances can be found in the Au NAs under 545 nm light illumination as shown in Fig. 6(c) and 6(d), which may improve the radiative recombination rate of excitons in CsPbBr3-xIx NCs. The electric field simulation result of Au NAs is in well agreement with PL enhancement of CsPbBr3-xIx NCs. Therefore, the enhanced PL emission is attributed to LSPR and gap plasmon resonances.
Fig. 6. The simulated electric field distribution of Au NAs with 325 nm (a, b) and 545 nm (c, d) incident wavelength.
4. Conclusion
In summary, CsPbBr3-xIx NCs are synthesized by the hot injection method. The PL intensity of CsPbBr3-xIx NCs is successfully improved by the ordered plasmonic Au NAs. The reflection spectra reveal that such enhancement is ascribed to a well match between the excitation/ emission of CsPbBr3-xIx NCs and LSPR/gap plasmon resonances absorption of Au NAs, resulting in the absorption and emission enhancement of CsPbBr3-xIx NCs. Additionally, TRPL indicates that the radiative decay rate is accelerated by Au NAs, then PL intensity is enhanced. This work might be helpful for further understanding the mechanism between LSPR and perovskite NCs for future applications.
Funding
National Natural Science Foundation of China (51902179, 51872161); Natural Science Foundation of Shandong Province (ZR2019BF019).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Supplemental document
See Supplement 1 for supporting content.
References
1. L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Krieg, R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh, and M. V. Kovalenko, “Nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I): novel opto-electronic materials showing bright emission with wide color gamut,” Nano Lett. 15(6), 3692–3696 (2015). [CrossRef]
2. J. R. Zhang, G. Hodes, Z. W. Jin, and S. Z. Liu, “All-inorganic CsPbX3 perovskite solar cells: progress and prospects,” Angew. Chem., Int. Ed. 58(44), 15596–15618 (2019). [CrossRef]
3. Y. Q. Wu, H. M. Wei, L. M. Xu, B. Q. Cao, and H. B. Zeng, “Progress and perspective on CsPbX3 nanocrystals for light emitting diodes and solar cells,” J. Appl. Phys. 128(5), 050903 (2020). [CrossRef]
4. H. L. Wang, Z. J. Dong, H. C. Liu, W. P. Li, L. Q. Zhu, and H. N. Chen, “Roles of organic molecules in inorganic CsPbX3 perovskite solar cells,” Adv. Energy Mater. 11(1), 2002940 (2021). [CrossRef]
5. Y. Chen, X. J. Liang, J. P. Liu, S. Q. Chen, and W. D. Xiang, “Environmentally friendly and ultrastable narrow-band emitter: CsPbX3@SEBS flexile film for light-emitting diode displays,” ACS Sustainable Chem. Eng. 9(30), 10291–10298 (2021). [CrossRef]
6. C. Chen, T. T. Xuan, W. H. Bai, T. L. Zhou, F. Huang, A. Xie, L. Wang, and R. J. Xie, “Highly stable CsPbI3:Sr2+ nanocrystals with near-unity quantum yield enabling perovskite light-emitting diodes with an external quantum efficiency of 17.1%,” Nano Energy 85, 106033 (2021). [CrossRef]
7. Z. B. Zhang, R. Ji, M. Kroll, Y. J. Hofstetter, X. K. Jia, D. B. Koch, F. Paulus, M. Löffler, F. Nehm, K. Leo, and Y. Vaynzo, “Efficient Thermally Evaporated γ-CsPbI3 Perovskite Solar Cells,” Adv. Energy Mater. 11(29), 2100299 (2021). [CrossRef]
8. S. Ullah, J. M. Wang, P. X. Yang, L. L. Liu, Y. Q. Li, A. U. Rehman, S. E. Yang, T. Y. Xia, H. Z. Guo, and Y. S. Chen, “Evaporation deposition strategies for all-Inorganic CsPb(I1-xBrx)3 perovskite solar cells: recent advances and perspectives,” Sol. RRL 5(8), 2100172 (2021). [CrossRef]
9. J. Z. Ye, M. M. Byranvand, C. O. Martnez, R. L. Z. Hoye, M. Saliba, and L. Polavarapu, “Defect passivation in lead-halide perovskite nanocrystals and thin films: toward efficient LEDs and solar cells,” Angew. Chem., Int. Ed. 60(40), 21636–21660 (2021). [CrossRef]
10. N. Shasmal and B. Karmakar, “Enhancement of photoluminescence in white light emitting glasses by localized surface plasmons of Ag and Au nanoparticles,” Chem. Phys. Lett. 754, 137713 (2020). [CrossRef]
11. N. Wang, Y. Wang, N. Ding, Y. J. Wu, L. Zi, S. Liu, D. L. Zhou, J. Y. Zhu, X. Bai, W. Xu, and H. W. Song, “Three-order fluorescence enhancement of perovskite nanocrystals using plasmonic Ag@SiO2 nanocomposites,” J. Mater. Chem. C 9(24), 7745–7752 (2021). [CrossRef]
12. M. G. Gong, M. Alamri, D. Ewing, S. M. Sadeghi, and J. Z. Wu, “Localized surface plasmon resonance enhanced light absorption in AuCu/CsPbCl3 core/shell nanocrystals,” Adv. Mater. 32(26), 2002163 (2020). [CrossRef]
13. A. Perveen, L. G. Deng, A. Muravitskaya, D. Yang, and H. Z. Zhong, “Enhanced emission of in-situ fabricated perovskite-polymer composite films on gold nanoparticle substrates,” Opt. Mater. Express 10(7), 1659–1674 (2020). [CrossRef]
14. A. Perveen, X. Zhang, J. L. Tang, D. B. Han, S. Chang, L. G. Deng, W. Y. Ji, and H. Z. Zhong, “Sputtered gold nanoparticles enhanced quantum dot light-emitting diodes,” Chin. Phys. B 27(8), 086101 (2018). [CrossRef]
15. S. Ye, M. H. Yu, W. Yan, J. Song, and J. L. Qu, “Enhanced photoluminescence of CsPbBr3@Ag hybrid perovskite quantum dots,” J. Mater. Chem. C 5(32), 8187–8193 (2017). [CrossRef]
16. Y. H. Zhang, H. Q. Sun, S. Zhang, S. P. Lia, X. Wang, X. Zhang, T. Y. Liu, and Z. Y. Guo, “Enhancing luminescence in all-inorganic perovskite surface plasmon light emitting diode by incorporating Au-Ag alloy nanoparticle,” Opt. Mater. 89, 563–567 (2019). [CrossRef]
17. F. Y. Juan, Y. Q. Wu, B. B. Shi, M. X. Wang, M. Wang, F. Xu, J. B. Jia, H. M. Wei, T. Z. Yang, and B. Q. Cao, “Plasmonic Au nanooctahedrons enhance light harvesting and photocarrier extraction in perovskite solar cell,” ACS Appl. Energy Mater. 4(4), 3201–3209 (2021). [CrossRef]
18. Q. A. Akkerman, V. D’Innocenzo, S. Accornero, A. Scarpellini, A. Petrozza, M. Prato, and L. Manna, “Tuning the optical properties of cesium lead halide perovskite nanocrystals by anion exchange reactions,” J. Am. Chem. Soc. 137(32), 10276–10281 (2015). [CrossRef]
19. X. F. Zhang, B. Lan, S. C. Wang, P. Gao, T. S. Liu, J. Y. Rong, F. Xiao, L. C. Wei, H. Y. Lu, C. Pang, L. Fan, W. L. Zhang, and H. B. Lu, “Low-dose X-ray excited photodynamic therapy based on NaLuF4:Tb3+-rose bengal nanocomposite,” Bioconjugate Chem. 30(8), 2191–2200 (2019). [CrossRef]
20. F. Y. Juan, F. Xu, M. Wang, M. X. Wang, G. Z. Hou, J. Xu, H. M. Wei, Y. H. Wang, Y. Q. Wu, and B. Q. Cao, “Photoluminescence enhancement of perovskite CsPbBr3 quantum dots by plasmonic Au nanorods,” Chem. Phys. 530, 110627 (2020). [CrossRef]
21. F. Xu, X. B. Kong, W. Z. Wang, F. Y. Juan, M. X. Wang, H. M. Wei, J. K. Li, and B. Q. Cao, “Quantum size effect and surface defect passivation in size-controlled CsPbBr3 quantum dots,” J. Alloys Compd. 831, 154834 (2020). [CrossRef]
22. G. Nedelcu, L. Protesescu, S. Yakunin, M. I. Bodnarchuk, M. J. Grotevent, and M. V. Kovalenko, “Fast anion-exchange in highly luminescent nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, I),” Nano Lett. 15(8), 5635–5640 (2015). [CrossRef]
23. Y. Q. Wu, S. B. Lin, W. Y. Shao, X. W. Zhang, J. Xu, L. W. Yu, and K. J. Chen, “Enhanced up-conversion luminescence from NaYF4:Yb,Er nanocrystals by Gd3+ ions induced phase transformation and plasmonic Au nanosphere arrays,” RSC Adv. 6(105), 102869 (2016). [CrossRef]
24. G. Z. Hou, Z. Y. Wang, H. G. Ma, Y. Ji, L. W. Yu, J. Xu, and K. J. Chen, “High-temperature stable plasmonic and cavity resonances in metal nanoparticle-decorated silicon nanopillars for strong broadband absorption in photothermal applications,” Nanoscale 11(31), 14777–14784 (2019). [CrossRef]
25. J. H. Yun, A. Y. Polyakow, K. C. Kim, Y. T. Yu, D. Lee, and I. H. Lee, “Enhanced luminescence of CsPbBr3 perovskite nanocrystals on stretchable templates with Au/SiO2 plasmonic nanoparticles,” Opt. Lett. 43(10), 2352–2355 (2018). [CrossRef]
26. C. Y. Cho, S. J. Lee, J. H. Song, S. H. Hong, S. M. Lee, Y. H. Cho, and S. J. Park, “Enhanced optical output power of green light-emitting diodes by surface plasmon of gold nanoparticles,” Appl. Phys. Lett. 98(5), 051106 (2011). [CrossRef]
27. I. H. Lee, L. W. Jang, and A. Y. Polyakov, “Performance enhancement of GaN-based light emitting diodes by the interaction with localized surface plasmons,” Nano Energy 13, 140–173 (2015). [CrossRef]
28. J. J. Liu, X. X. Sheng, Y. Q. Wu, D. K. Li, J. C. Bao, Y. Ji, Z. W. Lin, X. X. Xu, L. W. Yu, J. Xu, and K. J. Chen, “All-inorganic perovskite quantum dots/p-Si heterojunction light-emitting diodes under DC and AC driving modes,” Adv. Opt. Mater. 6(2), 1700897 (2018). [CrossRef]
29. J. J. Liu, X. J. Zhang, Y. Ji, X. X. Sheng, H. G. Ma, X. X. Xu, L. W. Yu, J. Xu, and K. J. Chen, “Rational energy band alignment and Au nanoparticles in surface plasmon enhanced Si-based perovskite quantum dot light-emitting diodes,” Adv. Opt. Mater. 6(19), 1800693 (2018). [CrossRef]
30. Y. Meng, X. Y. Wu, Z. Y. Xiong, C. Y. Lin, Z. H. Xiong, E. Blount, and P. Chen, “Electrode quenching control for highly efficient CsPbBr3 perovskite light-emitting diodes via surface plasmon resonance and enhanced hole injection by Au nanoparticles,” Nanotechnology 29(17), 175203 (2018). [CrossRef]
31. W. H. Zhang, F. Ding, and S. Y. Chou, “Large enhancement of upconversion luminescence of NaYF4:Yb3+/Er3+ nanocrystal by 3D plasmonic nano-antennas,” Adv. Mater. 24(35), OP236–OP241 (2012). [CrossRef]
32. H. Hulkkonen, A. Sah, and T. Niemi, “All-metal broadband optical absorbers based on block copolymer nanolithography,” ACS Appl. Mater. Interfaces 10(49), 42941–42947 (2018). [CrossRef]
33. A. Sundaramurthy, K. B. Crozier, G. S. Kino, D. P. Fromm, P. J. Schuck, and W. E. Moerner, “Field enhancement and gap-dependent resonance in a system of two opposing tip-to-tip Au nanotriangles,” Phys. Rev. B 72(16), 165409 (2005). [CrossRef]
