Herein, we present a novel low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) pixel circuit for a micro light-emitting diode (μLED) display based on pulse width modulation (PWM). By adopting PWM, we could achieve 10-bit gray levels of μLED without wavelength shift, which is a challenge in the realization of μLEDs. Furthermore, the proposed circuit compensated for the variation in threshold voltage (VTH) without an external sensing system. We simulated the error rate of the μLED emission time of the proposed pixel circuit depending on the VTH change. We measured the wavelength shift of the μLED using the fabricated circuit. This shift in PWM was smaller than that in pulse amplitude modulation (PAM). Consequently, the proposed pixel circuit could overcome screen distortions caused by color shifts of μLED displays using PWM techniques.

For low-temperature solution-processed perovskite solar cells, ZnO as an electron transport layer (ETL) has been studied instead of TiO₂ requiring high sintering temperature. However reports have been scarce about successful fabrication of perovskite solar cells based on the solution-processed ZnO ETL under atmospheric air. In this study, we found a possible mechanism to cause poor performance of the perovskite solar cells, which can be ascribed to chemical reactions between the methylammonium iodide (MAI) of the perovskite precursor (MAPbI₃) solution and the ZnO film under humid conditions. The MAI solution could etch out ZnO ETL and promote serious carrier recombination if processed in air, whereas there was no such reaction for processing in a glovebox (H₂O < 0.1 ppm). In order to suppress the reactions in air-ambient, we applied a simple and novel dynamic spin-coating process, dripping the perovskite precursor solution on ZnO during the spin-coating process, followed by an anti-solvent washing treatment. Using this approach, for the first time, the interfacial reaction of ZnO/MAPbI₃ was significantly suppressed and thus a power conversion efficiency of the perovskite solar cells fully-processed in air-ambient was enhanced from 0% to 11.2%. These experimental results pave the way for the development of perovskite solar cells under low-temperature processing in air-ambient.

Nanoscale MoS₂ has attracted extensive attention for sensing due to its superior properties.