@article{amoah_fu_yin_dong_dong_so_2022, title={Curved Mirror Arrays for Light Extraction in Top-Emitting Organic Light-Emitting Diodes}, volume={2}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.1c21128}, abstractNote={The light outcoupling efficiency of a top-emitting organic light-emitting diode (OLED) is only about 20%, and the majority of the light is trapped in the waveguide modes and surface plasmon polariton (SPP) modes. Extracting the trapped modes can reduce the device power consumption and improve the operating lifetime. In this study, we demonstrate a top-emitting OLED structure with a dielectric spacer to suppress the SPP mode and with a patterned back mirror to extract the waveguide modes. We examine and compare several curved mirror arrays and conclude that a micromirror array (μMA) can efficiently extract the waveguide modes while minimizing the absorption loss. The optimized μMA device with a semi-transparent top electrode shows a 36% external quantum efficiency, 2 times higher than the referenced device. This optical design can be easily incorporated into a top-emitting device and has a great potential for displays and lighting applications.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Amoah, Stephen and Fu, Xiangyu and Yin, Shichen and Dong, Qi and Dong, Chen and So, Franky}, year={2022}, month={Feb}, pages={9377–9385} }
 @article{yin_ho_ding_fu_zhu_gullett_dong_so_2022, title={Enhanced Surface Passivation of Lead Sulfide Quantum Dots for Short-Wavelength Photodetectors}, volume={34}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.2c00293}, abstractNote={Lead sulfide (PbS) quantum dots are promising solution-processed materials for short-wave infrared (SWIR) photodetectors due to their tunable band gap and solution processability. Phase-transfer ligand exchange is a common method to prepare quantum dot (QD) inks used in device fabrication. For large-sized PbS QDs used for SWIR detection, the conventional phase-transfer ligand exchange has been problematic due to the densely packed organic ligands and charge-neutral (100) facets. Here, we report a new strategy to carry out the efficient phase-transfer ligand exchange in large-sized QDs. Specifically, using lead acetate trihydrate (PbAc2·3H2O) as a precursor and methylammonium acetate (MAAc) as an additive in the ligand solution, we can facilitate the efficient phase-transfer ligand exchange and epitaxial growth of perovskite intermediate (MAPbI3–xAcx) on the (100) facets, resulting in a significant improvement in film quality suitable for device fabrication. The resulting photodiodes show a 2.5× enhancement in external quantum efficiency (EQE) compared to devices using QD inks obtained using the conventional method. Considering the low transmittance of the ITO electrode in the SWIR regime, our devices exhibit an internal quantum efficiency of over 90%.}, number={12}, journal={CHEMISTRY OF MATERIALS}, author={Yin, Shichen and Ho, Carr Hoi Yi and Ding, Shuo and Fu, Xiangyu and Zhu, Liping and Gullett, Julian and Dong, Chen and So, Franky}, year={2022}, month={Jun}, pages={5433–5442} }
 @article{dong_fu_cao_amoah_gundogdu_li_so_2020, title={Multi-mode Organic Light-Emitting Diode to Suppress the Viewing Angle Dependence}, volume={12}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.0c05825}, abstractNote={A typical top emitting OLED has a strong microcavity effect because of the two reflective electrodes. The cavity effect causes a serious color shift with the viewing angles and restricts the organic layer thickness. To overcome these drawbacks, we designed a multi-mode OLED structure having dual-dielectric spacer layers, which extend the cavity length by more than 10 times. This design completely eliminates the intrinsic cavity effect caused by the top and bottom boundaries respectively and provides freedom for the organic layer thickness. We demonstrate these effects in a white multi-mode OLED using a white emitter, which shows a negligible angular chromaticity shift of 0.006 from 0° to 70° and a Lambertian emission profile. The simple design and the perfect angular color profiles make the multi-mode OLED structure promising in large-area displays and solid-state lighting applications.}, number={28}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Dong, Chen and Fu, Xiangyu and Cao, Linyu and Amoah, Stephen and Gundogdu, Kenan and Li, Jian and So, Franky}, year={2020}, month={Jul}, pages={31667–31676} }
 @article{dong_fu_amoah_rozelle_shin_salehi_mendes_so_2019, title={Eliminate angular color shift in top-emitting OLEDs through cavity design}, volume={27}, ISSN={["1938-3657"]}, DOI={10.1002/jsid.792}, abstractNote={OLEDs suffer from viewing angle dependent spectral shift due to microcavity effects. To address this issue, we introduce a novel top‐emitting OLED with a dielectric spacer that forms multiple cavity modes. The resulting device shows almost no color shift at different viewing angles.}, number={8}, journal={JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY}, author={Dong, Chen and Fu, Xiangyu and Amoah, Stephen and Rozelle, Adam and Shin, Dong-Hun and Salehi, Amin and Mendes, Juliana and So, Franky}, year={2019}, month={Aug}, pages={469–479} }
 @article{dong_liu_barange_lee_pardue_yi_yin_so_2019, title={Long-Wavelength Lead Sulfide Quantum Dots Sensing up to 2600 nm for Short-Wavelength Infrared Photodetectors}, volume={11}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.9b16539}, abstractNote={Lead sulfide nanoparticles (PbS NPs) are used in the short wavelength infrared (SWIR) photodetectors because of their excellent photosensitivity, bandgap tunability, and solution processability. It has been a challenge to synthesize high quality PbS NPs with an absorption peak beyond 2000 nm. In this work, using PbS seed crystals with an absorption peak at 1960 nm, we report a successful synthesis of very large mono-dispersed PbS NPs having a diameter up to 16 nm by multiple injections. The resulting NPs have an absorption peak over 2500 nm with a small full-width-at-half-maximum (FWHM) of 24 meV. To demonstrate the applications of such large QDs, broadband heterojunction photodetectors are fabricated with the large PbS QDs of an absorption peak at 2100 nm. The resulting devices have an EQE of 25% (over 50% IQE) at 2100 nm corresponding to a responsivity of 0.385 A/W, and an EQE ~60% in the visible range.}, number={47}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Dong, Chen and Liu, Shuyi and Barange, Nilesh and Lee, Jaewoong and Pardue, Tyler and Yi, Xueping and Yin, Shichen and So, Franky}, year={2019}, month={Nov}, pages={44451–44457} }
 @article{salehi_dong_shin_zhu_papa_thy bui_castellano_so_2019, title={Realization of high-efficiency fluorescent organic light-emitting diodes with low driving voltage}, volume={10}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/s41467-019-10260-7}, DOI={10.1038/s41467-019-10260-7}, abstractNote={Abstract It is commonly accepted that a full bandgap voltage is required to achieving efficient electroluminescence (EL) in organic light-emitting diodes. In this work, we demonstrated organic molecules with a large singlet-triplet splitting can achieve efficient EL at voltages below the bandgap voltage. The EL originates from delayed fluorescence due to triplet fusion. Finally, in spite of a lower quantum efficiency, a blue fluorescent organic light-emitting diode having a power efficiency higher than some of the best thermally activated delayed fluorescent and phosphorescent blue organic light-emitting diodes is demonstrated. The current findings suggest that leveraging triplet fusion from purely organic molecules in organic light-emitting diode materials offers an alternative route to achieve stable and high efficiency blue organic light-emitting diodes.}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Salehi, Amin and Dong, Chen and Shin, Dong-Hun and Zhu, Liping and Papa, Christopher and Thy Bui, Anh and Castellano, Felix N. and So, Franky}, year={2019}, month={May} }
 @article{yu_liu_baek_kim_dong_so_2016, title={Solution-processed copper oxide interlayers for broadband PbS quantum-dot photodiodes}, volume={4}, ISSN={["2050-7534"]}, DOI={10.1039/c6tc03531k}, abstractNote={Metal oxide interlayers are promising for optoelectronic applications due to solution processability, optical transparency, and excellent charge blocking properties.}, number={47}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Yu, Hyeonggeun and Liu, Shyui and Baek, Sujin and Kim, Do Young and Dong, Chen and So, Franky}, year={2016}, month={Dec}, pages={11205–11211} }