Vibrational Property-Driven NIR Transparency in X:ZnO (X = Mo, Al) Multilayer Transparent Electrodes for Self-Powered Flexible Optoelectronics

In the direction of harnessing the benefit of untapped IR solar radiation, this work highlights the essence of developing Vis-NIR transparent conducting electrodes (TCEs) based on X:ZnO (X = Mo, Al) with embedded Al. The origin of NIR transparency is explained through a comparative study in MZO- and AZO-based frameworks, synthesized by magnetron sputtering operated at relatively low sputtering power, aiming at the application in optoelectronic devices as top-illuminating electrodes. A different type of microstructural array is proposed for obtaining better transparency in multilayered transparent conducting oxides (TCOs) with embedded metal nanostructures. The cutoff wavelength of the transparent window obtained experimentally is mainly explained by vibrational properties in terms of phonon modes derived from theoretical calculations involving first-principles density functional theory (DFT) as well as Raman studies. Also, the mechanical stability is tested and discussed based on strain delocalization. Finally, a device application of the developed TCOs is demonstrated with an emerging S-scheme heterojunction having the potential for self-powered optoelectronics, along with the mechanical flexibilities of the device and the TCE.