Self-Driven Photodetectors Based On Si Nanostructures:Fabrication And Performance

Photodetector is a typical optoelectronic device,which is employed to process and identify optical signals.Moreover,semiconductor-based photodetector is the significant part for achieving mechatronics.It is also crucial for a variety of applications,including light communication,biomedical sensing,imaging systems,environmental monitoring.To meet the demands of next-generation optoelectronic circuits,production and living,the design and construction of photodetectors with a tunable photoresponse range,self-powered and high detection performance features are urgently required.Therefore,the main research content of this dissertation is to design functional photodetectors based on different Si nanostructures.The main contents of the dissertation are as follows:(1)Si nanowire(NW)arrays/P3HT(Poly(3-hexylthiophene)).A metal-assisted chemical etching method is used to prepare Si NW arrays with a relatively large area.The NW are approximately 200 nm in diameter and approximately 3 μm in length.Then,a simple solution spin-coating method was used to prepare a P3HT film onto Si surface to form a heterojunction.By changing the concentration of P3HT solution,the core-shell heterojunction structure and the embedded heterojunction structure are successfully fabricated.It is found that both types of photodetectors can achieve self-driving and fast response speed.The difference is that the core-shell heterojunction can achieve a wide spectral response from 300 to 1100 nm,while the embedded heterojunction acts as a selective response photodetector with red and near-infrared light response(650-1 100 nm).(2)Si NW arrays/CuIno.7Ga0.3Se2(CIGS)nanoparticles.ID NWs have strong trapping effect,which can exploit the optical signal efficiently.In this regard,we design a core-shell heterojunction structure consisted of a light-absorbing material CIGS film and Si NWs,which not only enhances the absorption of light but also greatly improves the separation and transfer of photogenerated electron-hole pairs.The photodetector exhibits good photosensitivity under 920 nm light irradiation with on-off ratio of 5.24×103,responsivity of 0.33 A W-1,specific detectivity of 1.6×1013 Jones,and photoresponse speed of 823/356μs at zero bias.It’s noteworthy that both the Si substrate and the CIGS film are very stable inorganic materials.Therefore,this work opens up an opportunity for designing and constructing highly sensitive,low cost,stable and self-driven optoelectronic devices.(3)Dual antireflection Si structure/perovskite.With the growing popularity of flexible electronics,Si has been brought into the flexible electronic field by researchers.So far,researchers have successfully etched Si down to 100 μm thick for excellent flexibility by using an alkaline solution.However,it has been reported that Si must be at least 180 μm thick to absorb light completely.Thus,flexibility and sufficient light absorption are hard to be achieved simultaneously.In order to solve this problem and broaden the application of flexible Si,we design the dual antireflection nanostructure of Si to improve the detectivity of incident optical signal.The photoresponse performances of Si devices(Si pyramid devices and Si dual antireflection devices)under white light illumination are compared,and it is confirmed that the dual antireflection structure exhibits the best performance.The device possesses an on-off ratio up to 3000 and the photocurrent of 60 μA at zero bias.