Reader TTS

ABSTRACT A flexible full-color micro-LED display with high mechanical robustness was fabricated by printing quantum dots (QDs) on a blue micro-LED array using standard photolithography. The

red and green colors yielded from QDs exhibit a better color gamut than conventional color filters. The light conversion efficiency was enhanced by adding TiO2 nanoparticles to the

QD-photoresist composite. This full-color micro-LED display was successfully mounted on various unusual substrates such as curved glass, fabrics, and human skin, enabling diverse

optoelectronic applications. In addition, wireless multi-channel visible light communication (VLC) based on the wavelength-division-multiplexing orthogonal-frequency-division-multiplexing

(WDM-OFDM) technique was demonstrated using a QD-based color micro-LED panel. A high data transmission rate of 1.9 Gbps was successfully obtained owing to the high electrical–optical

modulation bandwidth of the QD-based micro-LED panel. SIMILAR CONTENT BEING VIEWED BY OTHERS ADVANCING HIGH-PERFORMANCE VISIBLE LIGHT COMMUNICATION WITH LONG-WAVELENGTH INGAN-BASED

MICRO-LEDS Article Open access 25 March 2024 WEARABLE AND INTERACTIVE MULTICOLORED PHOTOCHROMIC FIBER DISPLAY Article Open access 14 February 2024 MINI-LED, MICRO-LED AND OLED DISPLAYS:

PRESENT STATUS AND FUTURE PERSPECTIVES Article Open access 18 June 2020 INTRODUCTION Recently, micro-light-emitting diodes (micro-LEDs) have emerged as next-generation display technology

because of their superior ability to withstand moisture and provide ultrahigh luminance, and long lifespan compared to organic light-emitting diode (OLED) displays and liquid crystal

displays (LCDs)1,2,3,4,5,6. Owing to these properties, researchers have applied micro-LEDs in smart wearable displays, automobile displays, stretchable displays, and outdoor signage4,7,8,9.

In addition, micro-LEDs can be used as transmitters in VLC due to their high switching rate, high energy efficiency, and high modulation bandwidth10,11. They can wirelessly transmit data at

high speeds. The radio frequency (RF) spectrum, the most used band in modern wireless communication systems, is already congested owing to the high demand for wireless data traffic12. VLC

systems, which modulate the visible light spectrum to facilitate data transmission, have been investigated to replace the congested radio spectrum for wireless communication. In addition,

the high bandwidth of the visible light spectrum can accommodate many users at high transmission rates for 5G communication applications13. Micro-LEDs have the potential to integrate

displays and wireless communication systems. However, the fabrication complexity increases with the decrease in the size of LED chips, which hinders the commercialization of the

products14,15. One of the issues in micro-LED displays is the realization of a full-color RGB display that meets the standard specifications required by modern displays16,17,18. The most

widely-used method for fabricating an RGB micro-LED display is to transfer the red (R), green (G), and blue (B) micro-LED arrays from three different epitaxial wafers on the target

substrate19. However, this approach has several challenges, such as aligning LEDs during the transfer process and electrical bonding between the LEDs and metal electrodes of display

backplanes, which could raise an issue to the production yield. Although prototypes of RGB micro-LED displays have been successfully demonstrated through the transfer method, the problem of

high production costs due to low transfer yield remains a challenge20. Unlike traditional methods, where three different LEDs are transferred to yield an RGB display, quantum dots (QDs) have

been used as a color conversion layer on a blue gallium nitride (GaN) micro-LED array21. These RGB LED pixels can simultaneously transmit data using different wavelengths of light, making

it possible to transmit a lot of data at once. However, it is still challenging to produce an RGB micro-LED array using a QD color conversion layer on flexible substrates for VLC. In this

work, we developed a patternable QD-photoresist (PR) for photolithography. This strategy facilitates the formation of full-color micro-LED displays without complicated transfer of sub-pixels

and avoids alignment issues during their assembly. We transferred a GaN-based flip-chip micro-LED array onto a flexible substrate with the micro-LED electrodes facing up. A QD color

conversion layer for the red and green sub-pixels was precisely defined by photolithography to yield a flexible full-color micro-LED display. Further, the micro-LED array with QD-PR acts as

the optical source for wavelength division multiplexing (WDM)-VLC and facilitates a high-speed VLC link for free-space applications using orthogonal frequency division multiplexing (OFDM).

R, G, and B pixels allow for separate data transmission at different wavelengths at the same time, enabling massive data transmission that is essential for light fidelity (LiFi)

communication. RESULTS FABRICATION OF FLEXIBLE MICRO-LED DISPLAY Different lift-off methods have been developed to transfer the micro-LED array depending on the growth substrate (Fig. 1a).

Chemical lift-off and laser lift-off (LLO) were used to release GaN-based micro-LED arrays from silicon and sapphire substrates, respectively. First, the micro-LED devices were formed on

silicon and sapphire substrates using standard semiconductor fabrication, including photolithography, etching, chemical vapor deposition (CVD), and metal deposition. During the chemical

lift-off, the underlying silicon was etched in a warm potassium hydroxide (KOH) solution to create a suspended micro-LED array, and the alignment of the array was supported using a set of

anchors, which were defined by mesa22. The second approach to release the micro-LED devices is LLO, which offers high efficiency and high throughput over a large area with almost negligible

damage to the devices23,24. A temporary substrate, pressure-sensitive adhesive (PSA) film, was used to hold the micro-LED array during the LLO. After the lift-off, a roll-based transfer

system was used to precisely pick up the array and print it on a foreign substrate with an adhesive layer (NOA 63)25. A completely automated system can offer various advantages, such as high

accuracy of the alignment of the micro-LED array, which facilitates the integration of the metal interconnections and a high transfer yield owing to the well-controlled applied pressure at

the rubber-based roller. A QD-based color conversion layer was defined on the blue GaN micro-LEDs using the standard photolithography for a practical micro-LED application with full-color

emission (Fig. 1b). This strategy has several advantages: first, the complex transfer of red and green sub-pixels can be skipped. Second, the active color conversion layer offers higher

efficiency and a better color gamut of the display than conventional color filters. Third, photolithography is compatible with standard fabrication and can be applied to large-area displays.

We developed a patternable QD-PR by mixing colloidal QDs in transparent negative PR (SU-8) at a specific concentration to achieve a high color conversion efficiency. After forming the

interlayers and metal interconnections on the micro-LED array, the QD-PR was patterned on the desired position to yield RGB pixels (Fig. 1c). The integrated full-color micro-LED display on a

6-μm polyethylene terephthalate (PET) substrate exhibited high mechanical flexibility (Fig. 1d). The red and green QD-PRs were well defined on the micro-LED display (inset of Fig. 1d).

Finally, the data transmission using the RGB micro-LEDs was demonstrated (Fig. 1e). PHOTOLITHOGRAPHICALLY PATTERNABLE QD-PR Figure 2 presents the development of QD-PRs. QD-PR arrays of 50 μm

× 50 μm were successfully patterned on a glass substrate with a height of 10.8 ± 0.5 μm for the red and green QD-PRs (Fig. 2a, left; Fig. 2b, left; Supplementary Figs. 1, 2). Unlike passive

color filters that are commonly used in current display technologies to block specific wavelengths for achieving the desired color, a QD-based active color conversion layer emits color at a

specific wavelength when excited by photons26. Considering the absorption spectra of QD-PRs, the red and green QDs exhibit high absorption at a wavelength of 450 nm, which is the peak

wavelength of the blue micro-LED device. When the QDs are excited by a photon that originates from the blue micro-LED, the QDs convert the light to red and green spectra at 630 and 530 nm,

respectively (Figs. 2a, b right; Supplementary Table 1). However, blue light leakage during color conversion remains an issue. Two strategies have been investigated to resolve this issue:

(1) controlling the QD concentration in the PR and (2) adding the scattering nanoparticles in the QD-PR. The color properties were investigated for different concentrations of QD-PR and

nanoparticle density to achieve an optimal QD-PR. The concentration of the red QDs changed from 10 to 50 wt%. According to the electroluminescence (EL) spectra, the red peak (630 nm)

increased as the concentration of the QDs in SU-8 increased, while the blue peaks almost diminished to zero. The corresponding color coordination of each concentration is plotted in a CIE

diagram, as shown in Supplementary Fig. 3. To achieve a high conversion efficiency, the QDs must be well-dispersed in the PR solution without aggregation. The aggregation of QDs leads to

fluorescence quenching, and the photoluminescence (PL) of the QDs significantly decreases27. Therefore, before mixing with the PR solution, the QDs are dispersed in cyclopentanone through

ultrasonication to prevent aggregation. The light conversion efficiency (_LCE_) is calculated using the formula: \(LCE = \frac{{I_{QD}}}{{I_{Blue} - I_{Blue,Leak}}}\), where, _I__QD_ is the

light intensity after the QD conversion, _I__Blue_ denotes the blue light from the GaN micro-LED chip, and _I__blue,Leak_ is the blue peak after the QD conversion. The _LCE_ of the red QD-PR

was 36% at a concentration of 50 wt%. However, a high concentration of QD in PR solution can hinder the development of the PR film, and polymer residues can remain on the substrate after

the process. This issue can be resolved by blending the scattering nanoparticles into the QD-PR solution28. TiO2 nanoparticles exhibit a high refractive index of 2.8 and can be utilized as

scattering enhancers in the QD color conversion layers. With the addition of TiO2 nanoparticles, the blue light absorption of the QDs can be enhanced as more light is transferred to the QDs.

The emitted light of QDs increases at the peak wavelength through photoluminescence because the total internal reflection is avoided due to the scattering effect of the nanoparticles. We

fixed the concentration of the green QDs at 30 wt% and mixed the TiO2 nanoparticles from 0 to 10 wt%. The resulting EL spectra and their corresponding color coordination are shown in Fig. 2d

and Supplementary Fig. 4, respectively. The _LCE_ was 43% for 10 wt% TiO2 in the QD-PR. For demonstrating the versatility of the QD-PRs, the red and green QD-PRs were defined on the LEDs to

form RGB pixels (Fig. 2e). Three distinct colors (red, green, and blue) were clearly visible when the LEDs were turned on. The corresponding normalized EL spectra are shown in Fig. 2F. In

addition, the color gamut of the RGB pixels was measured and plotted on the CIE 1976 chromaticity diagram (Fig. 2f). Notably, the QD-PRs exhibited a larger coverage area on the CIE diagram

than the NTSC and BT709, which are the standard for modern ultra-high definition (UHD) displays (Supplementary Table 2). FLEXIBLE FULL-COLOR MICRO-LED DISPLAY We developed a prototype of

full-color micro-LED display by patterning the optimized QD-PRs on a large-area micro-LED array (20 × 20 pixels) after the metal interconnection process (Supplementary Fig. 5). The

fabrication was performed on a 6-μm thick PET substrate, which provides low mechanical stiffness. Further, the fabricated display was connected to an external driving circuit via a flexible

printed circuit board (FPCB) for display operations (Supplementary Fig. 6, Supplementary Fig. 7). Moreover, an additional graphene heat spreading layer can be inserted between the micro-LED

array and the plastic substrate for better heat dissipation. Graphene distributes the central temperature of micro-LED heating evenly on a two-dimensional plane to facilitate uniform heat

dissipation (Supplementary Fig. 8)29. The letters ‘L,’ ‘E,’ and ‘D’ were encoded to the display driving unit and presented on the micro-LED display through line addressing (Fig. 3a;

Supplementary Movie 1). The full-color display operated stably without mechanical failure owing to its low bending stiffness when peeled off from the glass handling substrate and bent by a

tweezer (Fig. 3b, c; Supplementary Movie 2). To further validate the mechanical robustness of the micro-LED display, cyclic bending tests were performed. No significant change in the

luminance of the display was observed when it was bent and rolled on a rod with a bending radius of 3 mm (Fig. 3d; Supplementary Movie 3). In addition, the electrical properties of the

micro-LEDs were investigated during the cyclic bending test (Fig. 3e). The variation in the operating voltage was less than ~4.5% after 1000 bending cycles under operating current of 100 μA

(Fig. 3f). The change in operating voltage could be recovered when the display was flattened. In addition, the change in the luminance of the micro-LEDs and EL peak is negligible after the

cyclic bending test under currents of 100 μA, 500 μA, and 1 mA (Supplementary Fig. 9). Therefore, we can conclude that the slight variation in electrical properties and mechanical bending

did not affect the performance of the micro-LED display. The high mechanical flexibility could be attributed to the low bending stiffness of the display substrate and the isolation of each

micro-LED pixel. The good mechanical feature of the micro-LED display allows it to attach to various types of unusual surfaces, such as thin glass, fabric, and human skin, and provide

invariant properties even under deformation. A 3 µm-thick double-sided adhesive layer was utilized to give the display the ability to perform like a sticker that can attach on target

surfaces. As a demonstration, the ultrathin display was attached to a curved glass with a bending radius of 4 cm (Fig. 4a). Recently, augmented reality (AR)-embedded head-up displays have

grabbed much attention as the next-generation displays for automobiles. Micro-LED displays promise to deliver multiple advantages for automobile displays over conventional OLED displays,

such as high brightness, better reliability against moisture and high temperatures, and low power consumption. The flexible sticker-like micro-LED display offers a strategy to integrate the

displays on vehicles by simply attaching the display on curved windshields. A wearable display is another prominent application as it can effectively deliver the output information to the

users30. We attached the flexible micro-LED display on a knitted fabric to produce a wearable display (Fig. 4b). A wearable micro-LED display integrated with LiFi applications is a promising

approach to let users interact with the Internet of Things (IoT), in which the physical objects are connected to the digital network. In addition, Fig. 4c shows the operation of this

sticker-like micro-LED display on a soft surface like human skin. A conformal contact of the electronics systems and the human skin surface is strongly dependent on the mechanical properties

of the device including, Young’s modulus, thickness, stiffness, adhesion, and the Poisson’s ratio of each layout in the display system31,32. To achieve flawless contact with the skin, the

micro-LED display was fabricated by integrating materials with low stiffness that can adhere to the wrinkles of the skin surfaces. The low bending stiffness of the ultrathin micro-LED

display allows the system to perform with minimum degradation in both luminance and electrical properties due to deformations induced by human skin. As a result, the ultrathin micro-LED

display is conformally mounted on the human skin and operates robustly without failure. WIRELESS VLC BASED ON QD-BASED MICRO-LED ARRAY Micro-LEDs exhibit a high electrical–optical modulation

bandwidth, making them a suitable optical source for VLC applications. We demonstrated high-speed data transmission using QD-based color micro-LEDs enabled by the QD-PRs through the

WDM-OFDM scheme. The OFDM is a kind of digital multi-carrier scheme in which the bandwidth of an optical source is completely utilized to encode digital data on multiple subcarriers33. To

realize the 3–channel RGB communication link, WDM-VLCs that enabled the data to be individually carried by the three wavelengths of the RGB micro-LEDs were implemented. Figure 5a shows the

experimental setup of the communication link that consisted of the micro-LEDs with the QD-PRs as the optical sources and a commercial avalanche photodiode (APD) as the receiver. The VLC is

performed wirelessly in a free-space of 30 cm. The OFDM signals were generated using an arbitrary waveform generator (AWG) after MATLAB coding, and the signals at the receiver end were

received by an oscilloscope and processed in MATLAB, including fast Fourier transform and demodulation. For the high throughput of the WDM VLC link, dichroic filters were placed in front of

the APD to prevent optical crosstalk between the wavelengths. The frequency response of the GaN blue micro-LED was from 5 to 250 MHz, indicating that the system is above the noise level.

Therefore, it can be completely utilized by the OFDM scheme and can provide a large bandwidth for data transmission (Fig. 5b, Supplementary Fig. 10). We implemented the OFDM signals that

contained 256 subcarriers to occupy the bandwidth of the system. The bit allocation on each subcarrier is shown in Fig. 5c, which correlates with the achieved SNR values in Fig. 5d. Notably,

the red and green channels enabled by the QD-PR exhibit fewer allocated bits than the blue channel because the long fluorescence lifetime of the QDs limits the optical bandwidth of the

channel34. However, it is noteworthy that the QD-based color conversion layer exhibits shorter fluorescent lifetime than that of phosphor-based color filter, which provide not only better

color purity, but also improve the modulation bandwidth35. The BER for each subcarrier is shown in Fig. 5e. The total BER of the link was 5.41 × 10–4, which is below the forward error

correction (FEC) target (2 × 10–3). As a result, the blue channel showed the highest data rate of 964 Mbps, while the red and green channels exhibited the data rates of 529 and 460 Mbps,

respectively. Hence, a total of 1.9 Gbps data transmission was achieved when the optical filters were used at the receiver to allow the desired wavelength to be processed in the WDM VLC link

(Supplementary Table 3). DISCUSSION We successfully fabricated a flexible full-color micro-LED display with high mechanical flexibility using QD-PR as the color conversion layer on an array

of GaN micro-LEDs. The fabrication of the flexible micro-LED display through the roll-transfer method provides high accuracy in the alignment of the LEDs and high productivity while

preserving the performances of the devices during the process. In addition, the QD-based color conversion layers enable display size scalability as they can be defined via a

foundry-compatible photolithography process. The developed QD-based color micro-LED application in an OFDM-based WDM VLC system was analyzed, and a high data transmission rate of 1.9 Gbps

was achieved. The outstanding electrical-optical modulation properties of the micro-LEDs enable Gbps multi-channel VLC, which is difficult to be achieved by conventional light sources. A

combination of flexible micro-LED display and wireless data transmission may accelerate the development of next-generation technologies, such as the IoT, LiFi, and intelligent wearable

electronics. METHODS FABRICATION OF MICRO-LEDS GaN was epitaxially grown on silicon and sapphire wafers. n-GaN was etched by inductively coupled plasma-reactive ion etching (ICP-RIE) using

BCl3 and N2 plasma. To form an n-type ohmic contact, metal layers (Cr/Au: 3/50 nm) were deposited and annealed at 300 °C under a N2 atmosphere. Next, p-type ohmic contacts (Ni/Au: 10/50 nm)

were defined on p-GaN. A 100-nm thick silicon nitride passivation layer was deposited using plasma-enhanced chemical vapor deposition (PECVD). An etch mask (PR 4620) was generated to define

the geometry of the micro-LEDs, and the exposed regions were etched using ICP-RIE. Further, the micro-LED array was released from the substrate either using a chemical or laser-assisted

method. An adhesive layer (NOA 63) was spin-coated onto a thin PET substrate, which was attached to a handling substrate with a layer of polydimethylsiloxane (PDMS). The micro-LED array was

then printed on the target substrate using an automated roll transfer system. PREPARATION OF QD-PR CdSe/ZnS core-shell QDs (Fine Lab) are used. The QD/toluene solution was stirred using a

magnetic bar to evaporate the solvent at room temperature. Further, the QDs were dispersed in SU-8 Thinner (MicroChem) in an ultrasonic bath. After confirming the absence of the aggregation

of the QDs, a transparent negative photoresist, SU-8 2015 (MicroChem), was added to the solution and stirred at 150 rpm overnight in an ambient environment. PHOTOLUMINESCENCE AND

ELECTROLUMINESCENCE MEASUREMENT The PL of the QDs was obtained using a Raman spectrometer (Horiba, LabRAM ARAMIS) with an external laser source of 325 nm. The EL characteristics of the

micro-LEDs with QD-PRs were obtained using a spectroradiometer (Konica Minolta, CS2000) with Keithley 2635A source meter. VLC LINK The OFDM signals are generated using an AWG (Tektronix,

AWG7002A). These signals were DC-biased with a bias-tee (Mini-Circuits, ZFSCJ-2-2-S) and fed to the micro-LEDs. At the receiver, an APD (Hamamatsu, C5331-11) detected the optical signal and

analyzed them using a digital oscilloscope (Tektronix, MSO71604C). The signals were processed offline through MATLAB. DATA AVAILABILITY The data that support the plots within these paper and

other findings of this study are available from the corresponding authors upon reasonable request. REFERENCES * Huang, Y., Hsiang, E.-L., Deng, M.-Y. & Wu, S.-T. Mini-LED, Micro-LED and

OLED displays: present status and future perspectives. _Light Sci. Appl._ 9, 105 (2020). Article  CAS  Google Scholar  * Park, S.-I. et al. Printed assemblies of inorganic light-emitting

diodes for deformable and semitransparent displays. _Science_ 325, 977–981 (2009). Article  CAS  Google Scholar  * Pust, P., Schmidt, P. J. & Schnick, W. A revolution in lighting. _Nat.

Mater._ 14, 454–458 (2015). Article  CAS  Google Scholar  * Wu, T. et al. Mini-LED and micro-LED: promising candidates for the next generation display technology. _Appl. Sci._ 8, 1557

(2018). Article  Google Scholar  * Zhang, H. & Rogers, J. A. Recent advances in flexible inorganic light emitting diodes: from materials design to integrated optoelectronic platforms.

_Adv. Opt. Mater._ 7, 1800936 (2019). Article  Google Scholar  * Hwangbo, S. et al. Wafer-scale monolithic integration of full-colour micro-LED display using MoS2 transistor. _Nat.

Nanotechnol._ 17, 500–506 (2022). Article  CAS  Google Scholar  * Lee, V. W., Twu, N. & Kymissis, I. Micro-LED technologies and applications. _J. Inf. Disp._ 32, 16–23 (2016). Google

Scholar  * Lee, Y. et al. Morphable 3D structure for stretchable display. _Mater. Today_ 53, 51–57 (2022). Article  CAS  Google Scholar  * Jang, B. et al. Auxetic meta-display: stretchable

display without image distortion. _Adv. Funct. Mater._ 32, 2113299 (2022). Article  CAS  Google Scholar  * Islim, M. S. et al. Towards 10 Gb/s orthogonal frequency division

multiplexing-based visible light communication using a GaN violet micro-LED. _Photon. Res._ 5, A35–A43 (2017). Article  CAS  Google Scholar  * Tsonev, D. et al. A 3-Gb/s single-LED

OFDM-based wireless VLC link using a gallium nitride μLED. _IEEE Photon. Technol. Lett._ 26, 637–640 (2014). Article  Google Scholar  * Karunatilaka, D., Zafar, F., Kalavally, V. &

Parthiban, R. LED based indoor visible light communications: state of the art. _IEEE Commun. Surv. Tutor._ 17, 1649–1678 (2015). Article  Google Scholar  * Feng, L. et al. Applying VLC in 5G

networks: architectures and key technologies. _IEEE Netw._ 30, 77–83 (2016). Article  Google Scholar  * Park, J. et al. Electrically driven mid-submicrometre pixelation of InGaN

micro-light-emitting diode displays for augmented-reality glasses. _Nat. Photon._ 15, 449–455 (2021). Article  CAS  Google Scholar  * Kim, R.-H. et al. Waterproof AlInGaP optoelectronics on

stretchable substrates with applications in biomedicine and robotics. _Nat. Mater._ 9, 929–937 (2010). Article  CAS  Google Scholar  * Choi, M. et al. Full-color active-matrix organic

light-emitting diode display on human skin based on a large-area MoS2 backplane. _Sci. Adv._ 6, eabb5898 (2020). Article  CAS  Google Scholar  * Han, H.-V. et al. Resonant-enhanced

full-color emission of quantum-dot-based micro LED display technology. _Opt. Express_ 23, 32504–32515 (2015). Article  CAS  Google Scholar  * Yin, Y. et al. Full-color micro-LED display with

CsPbBr3 perovskite and CdSe quantum dots as color conversion layers. _Adv. Mater. Technol._ 5, 2000251 (2020). Article  CAS  Google Scholar  * Bower, C. A. et al. Emissive displays with

transfer-printed assemblies of 8 μm× 15 μm inorganic light-emitting diodes. _Photon. Res._ 5, A23–A29 (2017). Article  CAS  Google Scholar  * Anwar, A. R. et al. Recent progress in

micro-LED-based display technologies. _Laser Photon. Rev._ 16, 2100427 (2022). Article  Google Scholar  * Kim, H.-M. et al. Ten micrometer pixel, quantum dots color conversion layer for high

resolution and full color active matrix micro-LED display. _J. Soc. Inf. Disp._ 27, 347–353 (2019). Article  CAS  Google Scholar  * Kim, H.-S. et al. Unusual strategies for using indium

gallium nitride grown on silicon (111) for solid-state lighting. _Proc. Natl Acad. Sci. USA_ 108, 10072–10077 (2011). Article  CAS  Google Scholar  * Bian, J. et al. Laser transfer,

printing, and assembly techniques for flexible electronics. _Adv. Electron. Mater._ 5, 1800900 (2019). Article  Google Scholar  * Kim, J., Kim, J.-H., Cho, S.-H. & Whang, K.-H. Selective

lift-off of GaN light-emitting diode from a sapphire substrate using 266-nm diode-pumped solid-state laser irradiation. _Appl. Phys. A_ 122, 305 (2016). Article  Google Scholar  * Choi, M.

et al. Stretchable active matrix inorganic light-emitting diode display enabled by overlay-aligned roll-transfer printing. _Adv. Funct. Mater._ 27, 1606005 (2017). Article  Google Scholar  *

Kim, H.-J., Shin, M.-H. & Kim, Y.-J. Optical efficiency enhancement in white organic light-emitting diode display with high color gamut using patterned quantum dot film and long pass

filter. _Jpn. J. Appl. Phys._ 55, 08RF01 (2016). Article  Google Scholar  * Noh, M. et al. Fluorescence quenching caused by aggregation of water-soluble CdSe quantum dots. _Colloids Surf. A

Physicochem. Eng. Asp._ 359, 39–44 (2010). Article  CAS  Google Scholar  * Kim, Y.-J. et al. 52.2: Invited Paper: application of quantum-dot patterned film with scattering nanoparticles for

the high efficiency displays. _SID Symp. Dig. Tech. Pap._ 50, 572–574 (2019). Article  CAS  Google Scholar  * Bae, S. H. et al. Graphene-based heat spreader for flexible electronic devices.

_IEEE Trans. Electron Devices_ 61, 4171–4175 (2014). Article  CAS  Google Scholar  * Lee, H. E. et al. Wireless powered wearable micro light-emitting diodes. _Nano Energy_ 55, 454–462

(2019). Article  CAS  Google Scholar  * Kim, J. et al. 2D Materials for skin-mountable electronic devices. _Adv. Mater._ 33, 2005858 (2021). Article  CAS  Google Scholar  * Liu, S. et al.

Strategies for body-conformable electronics. _Matter_ 5, 1104–1136 (2022). Article  CAS  Google Scholar  * Xie, E. et al. Over 10 Gbps VLC for long-distance applications using a GaN-based

series-biased micro-LED array. _IEEE Photon. Technol. Lett._ 32, 499–502 (2020). Article  CAS  Google Scholar  * Mei, S. et al. High-bandwidth white-light system combining a micro-LED with

perovskite quantum dots for visible light communication. _ACS Appl. Mater. Interfaces_ 10, 5641–5648 (2018). Article  CAS  Google Scholar  * Xiao, X. et al. Improving the modulation

bandwidth of LED by CdSe/ZnS quantum dots for visible light communication. _Opt. Express_ 24, 21577–21586 (2016). Article  CAS  Google Scholar  Download references ACKNOWLEDGEMENTS This work

was supported by the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) (NRF-2015R1A3A2066337), and the Research Program of Korea Institute of Machinery

& Materials (NK230D). AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * School of Electrical and Electronic Engineering, Yonsei University, Seoul, 03722, Republic of Korea Luhing Hu, Jaeyong

Choi, Sumin Hwangbo, Do-Hoon Kwon, Seunghyeon Ji, Sang-Kook Han & Jong-Hyun Ahn * Department of Nanomechanics, Nano-Convergence Mechanical Systems Research Division, Korea Institute of

Machinery & Materials (KIMM) 156 Gajeongbuk-ro, Yuseong-gu, Daejeon, 34103, Republic of Korea Bongkyun Jang & Jae-Hyun Kim Authors * Luhing Hu View author publications You can also

search for this author inPubMed Google Scholar * Jaeyong Choi View author publications You can also search for this author inPubMed Google Scholar * Sumin Hwangbo View author publications

You can also search for this author inPubMed Google Scholar * Do-Hoon Kwon View author publications You can also search for this author inPubMed Google Scholar * Bongkyun Jang View author

publications You can also search for this author inPubMed Google Scholar * Seunghyeon Ji View author publications You can also search for this author inPubMed Google Scholar * Jae-Hyun Kim

View author publications You can also search for this author inPubMed Google Scholar * Sang-Kook Han View author publications You can also search for this author inPubMed Google Scholar *

Jong-Hyun Ahn View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS J.-H.A. planned and supervised the project. L.H. conducted most of the

experiments regarding the device fabrication and characterized the properties of the devices. J.C., S.H., and S.J. supported the experiments. J.-H.K. and B.J. helped to transfer the

micro-LEDs. S.-K.H. and D.-H.K. investigated the VLC link. All authors analyzed the data and wrote the manuscript. CORRESPONDING AUTHORS Correspondence to Jae-Hyun Kim, Sang-Kook Han or

Jong-Hyun Ahn. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL INFORMATION PUBLISHER’S NOTE Springer Nature remains neutral with regard to

jurisdictional claims in published maps and institutional affiliations. SUPPLEMENTARY INFORMATION SUPPLEMENTARY MATERIALS FULL-COLOR MICRO-LED DISPLAY USING QD-BASED COLOR CONVERSION LAYERS.

THE OPERATION OF THE FULL-COLOR MICRO-LED DISPLAY DURING PEELING-OFF PROCESS. MECHANICAL TEST OF THE MICRO-LED DISPLAY. RIGHTS AND PERMISSIONS OPEN ACCESS This article is licensed under a

Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit

to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are

included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and

your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this

license, visit http://creativecommons.org/licenses/by/4.0/. Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Hu, L., Choi, J., Hwangbo, S. _et al._ Flexible micro-LED display

and its application in Gbps multi-channel visible light communication. _npj Flex Electron_ 6, 100 (2022). https://doi.org/10.1038/s41528-022-00234-z Download citation * Received: 09 July

2022 * Accepted: 14 December 2022 * Published: 26 December 2022 * DOI: https://doi.org/10.1038/s41528-022-00234-z SHARE THIS ARTICLE Anyone you share the following link with will be able to

read this content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing

initiative