This work reports the optoelectronic characteristics of the graphene/MAPbI<sub>3</sub>/TiO<sub>2</sub>/Si heterostructure and graphene/Pb<sub>2</sub>/porous Si heterostructure for light-emitting devices with low cost. The XRD diagrams of these two heterostructures show three main peaks at the position of 14.1°, 28.4°, and 31.9°, which correlate with (110), (220), and (310) planes of the MAPbI<sub>3</sub> perovskite phase. The PL spectra of these two heterostructures demonstrated three peaks located at 382, 566, and 766 nm. They are corresponding to the emission of B-B transition of TiO<sub>2</sub>, defects in the TiO<sub>2</sub>, and B-B transition of MAPbI<sub>3</sub>. One peak of the EL spectrum of the graphene/MAPbI<sub>3</sub>/TiO<sub>2</sub>/porous Si heterostructure operated under the injection current of 10 mA located at around 800 nm was observed.
This work proposes a novel white light device consisted of a yttrium aluminum garnet (YAG) phosphor-doped zinc oxide (ZnO) (ZnO:YAG) thin film deposited on a indium tin oxide (ITO) glass substrate by ultrasonic spray pyrolysis. Characteristics of the ZnO:YAG (YAG at 1, 5, and 10 wt%) film on ITO glass substrates were examined by x-ray diffraction (XRD) pattern, hall measurement, and photoluminescence (PL) pattern spectra. The color of the PL spectra of the yttrium-aluminum garnet (YAG) phosphor-doped zinc oxide (ZnO) thin films under excitation of He-Cd laser with wavelength of 325 nm is nearly white.