Preparation And Performance Study Of WO₃ Based UV Photodetector

Tungsten trioxide（WO₃）is a typical wide bandgap n-type semiconductor transition metal oxide with a large exciton binding energy（0.15 e V）,high light absorption coefficient(≥10⁴ cm^-1),and high phonon-limited electron mobility(12 cm² V^-1 s^-1),making it a highly sought-after semiconductor material for use in sensors,electrochromic applications,photodetectors,and other applications.The bandgap of WO₃ resonates with ultraviolet（UV）light,generating excess electrons that help to generate photocurrents.However,its application in photodetectors is limited by inherent disadvantages such as slow response time and current switching ratio.Currently,there is little research on WO₃-based photodetectors in general,and the equipment used to manufacture them is relatively complex and expensive.Therefore,suitable manufacturing processes and device structures need to be selected to make them better for real-life applications.This paper focuses on improving the optoelectronic properties of WO₃-based UV photodetectors by means of material compounding,morphology modulation,process optimization,and the design of different device structures.The main studies are as follows:（1）Heavy boron-doped diamond（BDD）films were prepared by chemical vapor deposition（CVD）,and WO₃ NRs（nanorods）were grown on the BDD films by hydrothermal means to form pn-junction tunneling diodes.The effects of their temperature-dependent negative differential resistance effect and carrier tunneling injection behavior on the optoelectronic performance of UV photodetectors at high temperatures were investigated.Their carrier transport performance under UV light（365 nm）irradiation in the temperature range of 30～300°C was also investigated.When the temperature was increased to 300℃,the photocurrent value reached as high as 0.11 A under the bias voltage of 5 V,and the device could still maintain a fast response speed（1.2 s）,proving that the detector had excellent thermal stability in a high-temperature environment.（2）Different morphologies of WO₃ were synthesized separately by controlling the concentration of the solution and were uniformly covered on the FTO by making a slurry as a photoanode for the photodetector.It was found that the UV photodetectors with different WO₃ morphologies showed good optoelectronic performance under the irradiation of UV light（365 nm）at a light power of 45 m W/cm².Among them,the UV photodetector with a sea urchin-like structure had the best photoresponse current and response speed.All three morphologies could maintain good cycling performance,and they could be operated in the mode without external bias.（3）The WO₃ seed crystal layer was prepared on the FTO surface by spin coating.Then,the WO₃ nanosheets were grown closely on the FTO by the hydrothermal method.The photochemical（PECC）type UV photoelectric detector was prepared using the WO₃nanosheets as photoanodes.Firstly,the photoelectric properties of WO₃ nanosheets at different annealing temperatures were investigated,and it was proved that the detector had the best photoelectric properties at annealing temperature of 300℃.In order to further investigate the factors affecting the magnitude of photocurrent,the photoelectric performance of WO₃ photoanodes was tested separately in H₂O,0.5 M H₂SO₄,and 0.5 M Na₂SO₄ at 300℃annealing temperature.By comparing the results in different electrolytes,it was found that the photocurrent was the largest in 0.5 M H₂SO₄,and it could also maintain a fast photoresponse rate.