Dursun, Ibrahim; Shen, Chao; Parida, Manas R.; Pan, Jun; Sarmah, Smritakshi P.; Priante, Davide; AlYami, Noktan Mohammed; Liu, Jiakai; Saidaminov, Makhsud I.; Alias, Mohd Sharizal; Abdelhady, Ahmed L.; Ng, Tien Khee; Mohammed, Omar F.; Ooi, Boon S.; Bakr, Osman(ACS Photonics, American Chemical Society (ACS), 2016-05-31)[Article]
Visible light communication (VLC) is an emerging technology that uses light-emitting diodes (LEDs) or laser diodes for simultaneous illumination and data communication. This technology is envisioned to be a major part of the solution to the current bottlenecks in data and wireless communication. However, the conventional lighting phosphors that are typically integrated with LEDs have limited modulation bandwidth and thus cannot provide the bandwidth required to realize the potential of VLC. In this work, we present a promising light converter for VLC by designing solution-processed CsPbBr3 perovskite nanocrystals (NCs) with a conventional red phosphor. The fabricated CsPbBr3 NCs phosphor-based white light converter exhibits an unprecedented modulation bandwidth of 491 MHz, which is ~ 40 times greater than that of conventional phosphors, and the capability to transmit a high data rate of up to 2 Gbit/s. Moreover, this perovskite enhanced white light source combines ultrafast response characteristics with a high color rendering index of 89 and a low correlated color temperature of 3236 K, thereby enabling dual VLC and solid-state lighting functionalities.
Varadhan, Purushothaman; Fu, Hui-chun; Priante, Davide; Duran Retamal, Jose Ramon; Zhao, Chao; Ebaid, Mohamed; Ng, Tien Khee; Ajia, Idris A.; Mitra, Somak; Roqan, Iman S.; Ooi, Boon S.; He, Jr-Hau(Nano Letters, American Chemical Society (ACS), 2017-02-08)[Article]
Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of −31 mA/cm at −0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only <4 h of photoelectrochemical stability. These findings shed new light on the importance of surface passivation of nanostructured photoelectrodes for photoelectrochemical applications.
Bose, Riya; Adhikari, Aniruddha; Burlakov, Victor M; Liu, Guangyu; Haque, Mohammed; Priante, Davide; Hedhili, Mohamed N.; Wehbe, Nimer; Zhao, Chao; Yang, Haoze; Ng, Tien Khee; Goriely, Alain; Bakr, Osman; Wu, Tao; Ooi, Boon S.; Mohammed, Omar F.(ACS Energy Letters, American Chemical Society (ACS), 2018-01-23)[Article]
Introducing dopants into InGaN NWs is known to significantly improve their device performances through a variety of mechanisms. However, to further optimize device operation under the influence of large specific surfaces, a thorough knowledge of ultrafast dynamical processes at the surface and interface of these NWs is imperative. Here, we describe the development of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) as an extremely surface-sensitive method to directly visualize in space and time the enormous impact of silicon doping on the surface-carrier dynamics of InGaN NWs. Two time regime dynamics are identified for the first time in a 4D S-UEM experiment: an early time behavior (within 200 picoseconds) associated with the deferred evolution of secondary electrons due to the presence of localized trap states that decrease the electron escape rate and a longer timescale behavior (several ns) marked by accelerated charge carrier recombination. The results are further corroborated by conductivity studies carried out in dark and under illumination.
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