ZnO UV sensor photoresponse enhancement by coating method optimization

Modern high-performance photodetector research is driven by the need to simultaneously improve multiple parameters, but also fit the decreasing size of electronics and maintain low production price.  Here, we demonstrated how our synthesized ZnO tetrapod (ZnO-T) nanostructure was deposited on electrodes with variating gap by four coating methods including drop casting, microdrop casting, spray coating and slot-die coating with the same thickness. Optimizing the inter-electrode gap and coating method the record I_UV/I_Dark ratio per unit area value of 8.73 × 10⁶ was obtained. The fastest rise time 0.78 s and fastest decay time 0.94 s were obtained by slot-die coated sensors. High photoresponse of ZnO-Ts, the inter-electrode gap size influences formation of ZnO-T microstructure during coating process and morphology influence on photoresponse was explained. We demonstrate that even with the same optimized ZnO-T nanostructures photoresponse can be improved by 2 orders of magnitude. Our work shows the importance of coating morphology and inter-electrode gap optimization.