Fast-acting halide-perovskite-based RGB fluorescent materials for aggregate Gb/s visible light communication
Item Type Conference Paper;Presentation
Authors Wang, Yue;Wang, Hong;Alkhazragi, Omar;Mohammed, Zyad O.F.;Gutierrez Arzaluz, Luis;Kang, Chun Hong;Ng, Tien Khee;Mohammed, Omar F.;Ooi, Boon S.
Citation Wang, Y., Wang, H., Alkhazragi, O., Mohammed, Z. O. F., Gutiérrez- Arzaluz, L., Kang, C. H., Ng, T. K., Mohammed, O. F., & Ooi, B.
S. (2023). Fast-acting halide-perovskite-based RGB fluorescent materials for aggregate Gb/s visible light communication. Optical Components and Materials XX. https://doi.org/10.1117/12.2647546 Eprint version Post-print
DOI 10.1117/12.2647546
Publisher SPIE
Rights This is an accepted manuscript version of a paper before final publisher editing and formatting. Archived with thanks to SPIE.
Download date 2023-12-16 22:34:15
Link to Item http://hdl.handle.net/10754/692368
Fast-acting halide-perovskite-based RGB fluorescent materials for aggregate Gb/s visible light communication
Yue Wang
a, Hong Wang
b, Omar Alkhazragi
a, Zyad O. F. Mohammed
a, Luis Gutiérrez-Arzaluz
b, Chun Hong Kang
a, Tien Khee Ng
a, Omar F. Mohammed
b, Boon S. Ooi*
aa
Photonics Laboratory, Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi
Arabia
b
Membranes and Porous Materials Center and KAUST Catalysis Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-
6900, Saudi Arabia
ABSTRACT
Three types of halide-perovskite-based fast-acting fluorescent materials have been demonstrated for high-speed visible light communication. All-inorganic metal-halide perovskite CsPbI3 was utilized to generate red color at 685 nm, and two- dimensional (2D) hybrid organic-inorganic halide perovskite nanosheets, (PEA)2PbI4 and (PEA)2PbBr4 (PEA= C8H9NH3), with peak photoluminescence (PL) wavelengths of 525 nm and 408 nm, were respectively used for green- and blue-light emission. The materials were then embedded in the polymethyl methacrylate (PMMA) to improve their durability and flexibility in practical applications. Pumped by a 405-nm violet laser, the red and green phosphors exhibit –3-dB modulation bandwidths of 14 MHz and 193 MHz, respectively. For the blue phosphor, a 124-MHz –3-dB bandwidth was obtained by using a 375-nm UVA laser diode. Benefitting from either the short PL lifetime or high PL quantum yield, aggregate Gb/s data transmission was achieved in the communication link. Direct current biased optical orthogonal frequency-division multiplexing (DCO-OFDM) modulation scheme was implemented with an adaptive quadrature amplitude modulation (QAM) signal. The transmission net data rates of RGB phosphors are 0.51 Gb/s, 0.93 Gb/s, and 0.43 Gb/s, respectively. The corresponding average bit error ratios are 3.5×10-3, 3.6×10-3, and 3.6×10-3, which are below the 7%-overhead forward error correction (FEC) criterion. Taking advantage of the tunability of the halide perovskite materials covering the whole visible range could further fulfill high-speed color-pure wavelength-division multiplexing by using a single source with multiple luminescent materials emitting light at different wavelengths. Besides, combining luminescent materials with specific colors, simultaneous white-light illumination, and high-speed communication can also be realized.
Keywords: Fast-acting RGB fluorescent materials, halide perovskites, visible light communication, orthogonal frequency- division multiplexing
1. INTRODUCTION
Color conversion technique has been widely used for white-light generation1, luminescent solar concentrator2, and wide field-of-view photodetection3. As the radio frequency band becomes more and more congested, optical wireless communication (OWC) has attracted substantial research interest in recent years. In an OWC link, color-converting materials with short radiative lifetime, high photoluminescence quantum yield (PLQY), narrow emission linewidth, and large wavelength tunability are always pursued to achieve high-speed and multi-channel communication.
Lead halide perovskite is a promising class of material to be applied as a fast-acting color-converting component in the visible-light communication (VLC) system, thanks to its facile synthesis, solution processability, and tunability of the emission wavelength via size and composition. Particularly with low-dimensional crystal structure, the narrower-band emission, shorter radiative lifetime, and higher exciton binding energy can be further observed with better quantum confinement4. In this work, red-green-blue (RGB) thin films were successfully made of bulk CsPbI3, 2D (PEA)2PbI4 and (PEA)2PbBr4 nanosheets, respectively, to attain aggregate Gb/s data transmission in the VLC system.
*[email protected]; phone 966 012-808-4360; https://cemse.kaust.edu.sa/photonics
2. MATERIAL PREPARATION AND CHARACTERIZATIONS
CsPbI3 powder was synthesized with the solvent-free mechanochemical process5, while 2D (PEA)2PbI4 and (PEA)2PbBr4
nanosheets powder were synthesized by dropping the precursor solutions into toluene and centrifuging to get the precipitate6. Three kinds of as-synthesized powder were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), as shown in Figure 1. The XRD patterns of 2D nanosheets showed periodic diffraction at low angles, indicative of nanosheet stacking. These periodicities correspond to the average spacing between layered nanosheets of 1.67 nm and 1.82 nm for (PEA)2PbBr4 and (PEA)2PbI4 nanosheets, respectively. The SEM images show individual and stacking nanosheets. In terms of the CsPbI3 powder, the presence of (100), (110), (200), (211), (211), and (220) diffraction peaks imply the formation of cubic or black phase CsPbI3. The TEM image in Figure 1(d) indicates the aggregate nanocrystal with an average diameter of 8.54±2.08 nm.
Figure 1. (a) XRD patterns of CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 powder, with the corresponding SEM images (b), (c), and TEM image (d).
The RGB thin films were then made by mixing the synthesized powder with polymethyl methacrylate (PMMA) in a chloroform solution, which was then dropped in a glass vial. The free-standing films were obtained after the solvent slowly evaporated, with the photographs shown in Figure 2. Embedding perovskite nanocrystals into the polymer can effectively enhance the stability and mechanical strength during practical operation. Subsequently, the absorption and emission behaviors of these RGB films were investigated with the normalized absorbance and PL spectra shown in Figure 2. The peak wavelength, full width at half maximum (FWHM), and absorption peak/range are extracted and listed in Table 1.
Figure 2. Normalized absorbance and PL spectra of CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films, with the corresponding photograph of the thin films made by embedding the perovskite into PMMA (under 365-nm illumination).
3 μm
3µm
(a)
(b)
(c)
(d)
(002)
(004) (006) (008)
(002)
(004) (006) (008)
(100) (110)
(200)
(211) (220)
Compared to bulked CsPbI3 crystal, (PEA)2PbI4 and (PEA)2PbBr4 thin films exhibit narrower PL emission and stronger excitonic absorption, indicating a higher exciton binding energy due to better quantum confinement with the nature of 2D Ruddlesden-Popper phase.
Table 1. Emission and absorption properties of RGB films.
Material Peak Emission Wavelength
FWHM of PL
Absorption peak/range
(PEA)2PbBr4 408 nm 11 nm 400 nm
(PEA)2PbI4 525 nm 15 nm 518 nm
CsPbI3 685 nm 36 nm <700 nm, peak at 416 nm
3. VISIBLE-LIGHT COMMUNICATION PERFORMANCE
The VLC system was established with the 375-nm/405-nm laser diode as the transmitter, an integrating sphere to place the RGB thin films, and a silicon-based avalanche photodetector (APD) as the receiver. The laser beam was coupled into the integrating sphere and focused on the thin film, and the fluorescence of the thin film was collected by APD. The small- signal frequency response was tested by a vector network analyzer, which was pre-calibrated and utilized to generate the modulation signal loaded and analyze the output electric signal from APD7. The normalized frequency responses of RGB thin films are shown in Figure 3(a). The –3-dB bandwidths were extracted as 14 MHz, 193 MHz, and 124 MHz for CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films, respectively. As the main factor that determines the modulation bandwidth, the PL lifetimes of all RGB thin films were measured using the time-correlated single-photon counting (TCSPC) technique.
By fitting the decay traces with exponential decay function, the average lifetimes were obtained of 13 ns, 0.53 ns, and 0.67 ns for CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films, respectively. These results are consistent with the relationship of f–3-dB≤1/(2π𝜏)8 and indicate that the perovskites with smaller grain sizes tend to have shorter PL lifetime and broader modulation bandwidth.
Figure 3. (a) Normalized frequency responses of CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films. (b) TCSPC decay traces of CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films.
To further verify the performance of RGB thin films as fast-acting color-converting components in OWC link, DC-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) was implemented, and the results are shown in Figure 4. In the test, the signal was sent to the transmitter with an arbitrary waveform generator, and the output signal was amplified and recorded by the oscilloscope for offline processing. With optimized bit and power loading, the aggregate Gb/s net data rate was achieved with 0.51 Gb/s, 0.93 Gb/s, and 0.43 Gb/s for CsPbI3, (PEA)2PbI4, and (PEA)2PbBr4 thin films, respectively. The corresponding average bit error ratios are 3.5×10-3, 3.6×10-3, and 3.6×10-3, which are below the
7%-overhead forward error correction (FEC) criterion. These promising data rates can be attributed to either the short PL lifetime or the high PLQY of the perovskite, which significantly broadened the usable bandwidth up to ~300 MHz and enhanced the signal-to-noise ratio (SNR) to around 20 dB.
Figure 4. DCO-OFDM implementation for (a) (PEA)2PbBr4, (b) (PEA)2PbI4, and (c) CsPbI3 thin films. (From top to bottom) The signal-to-noise ratios (SNRs) of each subcarrier; Channel capacities and allocated number of bits for each subcarrier, where the spectral efficiency (SE) is defined as the data rate (b/s) that can be sent over a unit frequency (Hz); Power loading
factors (PLFs) with received constellations; Bit error ratios (BERs) of each subcarrier.
4. CONCLUSION
In this work, we made a series of fast-acting color-converting thin films with lead halide perovskites. By adjusting the chemical composition of organic cations and halide anions, the emission wavelength can be tuned to cover almost the whole visible spectral range from 409 nm to 685 nm with different dimensionalities. By taking advantage of the strong quantum confinement, narrow emission linewidth, and short PL lifetime provided by 2D hybrid organic-inorganic perovskites [(PEA)2PbI4 and (PEA)2PbBr4], more than 100 MHz –3-dB bandwidth and more than 0.5 Gb/s net data rate were achieved. In terms of the CsPbI3, the sufficiently high fluorescence intensity ensured the high-speed data transmission in red color. With proper passivation with polymer, the stability and flexibility of the material have been substantially enhanced for practical operation. This study paved the way forward on the potential integration of lead halide perovskites in high-speed optical devices and modules for wide-band wavelength-division multiplexing or white-light illumination &
communication.
ACKNOWLEDGEMENT
This work was supported by King Abdullah University of Science and Technology (KAUST) (Grant No. BAS/1/1614-01- 01 & ORA-2022-5313) and the Office of Naval Research Global (Grant No. N62909-19-1-2079).
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