Strain mediated light emission using heterojunctions of all-inorganic mixed-halide perovskite nanocrystals via piezo-phototronic effect

Utilizing the superior luminescence properties and high color purity of inorganic perovskite nanocrystals (NCs), we report the fabrication of color-saturated CsPbBr3_xIx (x = 0-3)/ZnO heterojunctions based white light emitting diodes (LEDs) on a flexible platform. Here, bandgap engineered mixed halide perovskite NCs have been prepared by solution phase synthesis technique that was spin coated on sputtered ZnO film, acting as an electron injector layer as well as an efficient luminescent material. Broad (- 350-700 nm) electroluminescence (EL) emission features covering the near UV and entire visible region of the electromagnetic spectrum have been successfully achieved at an ambient (humidity - 50-55%) condition with comparatively lower forward bias (Vth - 2 V). Finally, we demonstrate the significant enhancement (up to - 75%) of EL intensity by applying an external stress owing to the piezoelectric properties of ZnO films. The modulation of energy band alignment in CsPbBr3/ZnO heterojunction due to the local strain induced positive piezo-potential in ZnO leads to an enhanced radiative recombination efficiency in CsPbBr3 domain, resulting in superior EL emission characteristics. The combinatorial fascinating optical properties of inorganic perovskites and piezo-phototronic effect of ZnO provide a promising platform to fabricate highly luminescent LEDs that may find perspective applications in highresolution flexible display devices and wearable electronics.