| In order to meet the wearable,portable,water media and other special environment for light or electrical parts.In this paper,ultrathin transparent conductive electrode films for flexible photodiodes are designed and fabricated by using related surface/interface modification methods.The mechanism of diode enhancement by hydroxyl modification under the interaction between ferroelectric thin film and water medium was studied.The mechanism of photodiode reversible enhancement generated by the reversible regulation of the band gap of double-layer perovskite under the stress was explored.The main research results are as follows:1.According to the characteristic matrix theory,interference theory and parallel resistance theory of optical thin film.The’sandwich’zinc oxide/metal/zinc oxide ultrathin transparent conductive film was prepared by selecting the metal material and design the matching thickness between the film layers.The results are as follows.When the silver film thickness is 8 nm and 11 nm,square resistance of zinc oxide/silver/zinc oxide is 6.1Ω·sq-1and 3.2Ω·sq-1 respectively.The highest transmittance in the range of visible light is 90%and 86%respectively.Zinc oxide/silver oxide/zinc oxide ultrathin transparent conductive films with good photoelectric properties were obtained.Copper and silver were selected as the interlayer metal.It is found that copper grows in a three-dimensional island pattern and silver grows in a planar pattern,easy to form a continuous film when the thickness is relatively thin,suitable for metal layer of’sandwich’.2.Nano-thin films of bismuth ferrite and barium titanate were prepared by pulsed laser deposition and laser molecular beam epitaxy.Based on the mechanism of double electric layer structure formed at the interface between ferroelectric thin film and water,the ferroelectric polarization can be reversed in a large area.At the same time,the surface of the film was modified with hydroxyl groups.The results are as follows.Forward current of the as grown bismuth ferrite film diode is 1.30×10-9 A,and current increased to 7.73×10-9 A after hydroxyl modification.Forward current of the as grown barium titanate film diode is2.13×10-7 A,and current increased to 1.11×10-5 A after hydroxyl modification.The direction of the diode in barium titanate film modified by hydroxyl groups can be adjustable.Under the action of hydroxyl groups,the depletion layer gets narrow due to the increase of oxygen vacancy concentration near the surface of bismuth ferrite film,and the diode effect is enhanced.The increase of oxygen vacancy concentration near the surface of barium titanate film causes the Schottky potential barrier go down,the diode effect is enhanced and the direction is adjustable.3.Double-layer perovskite cesium-silver-bismuth-bromide single crystal was prepared by supersaturated solution method.The surface of cesium-silver-bismuth-bromide was modified by micro-stress using a nano-probe as the top electrode and applying a micro-nano-scale mechanical load.The results are as follows.Under the macro,as the lighting power increased from 2.31 m W to 5.29 m W,the photocurrent of the device gradually increased to 0.81 n A.The micro,the measured photocurrent was up to 0.92 n A.According to first principles calculation,it is found that the application and removal of micro-nano-scale stress make the optical band gap retract and widen reversibly.Thus,the photodiode effect is reversibly enhanced.In summary,ultrathin transparent conductive silver-based films with good optical and electrical properties can be obtained by thickness matching macro modification regulation.The diode effect of inorganic perovskite bismuth ferrite and barium titanate was enhanced by hydroxyl modification.Micro-stress surface modification regulates the optical band gap of cesium-silver-bismuth-bromide,realizing the reversible enhancement of photodiodes.The composite of bismuth ferrite/barium titanate or cesium-silver-bismuth-bromide with ultra-thin transparent conductive electrode provides a potential application in flexible ultra-thin electronic devices. |
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