Visible light photoresponse properties of Ag/n-ZnO-NRs/p-Si/Al photodiodes, the influence of optimal ZnO precursor concentration via CBD method

In this study, we studied the influence of zinc nitrate hexahydrate (Zn(NO 3 ) 2 .6 H 2 O) precursor concentrations (0.03, 0.05, and 0.07 M) in Ag/n-ZnO-NRs/p-Si/Al photodiodes on the photoresponse of the samples to the blue, green, and red light LEDs. The layers were characterized by FESEM, EDX, XRD, PL, UV -Vis. reflectance spectra, and also, I -V and I -t in the dark and under light illuminations. We found, depending on the precursor concentration: (1) the ZnO layers, while having a polycrystalline structure with a hexagonal (wurtzite) phase mainly grown along the (002) direction, consist of nanorods (NRs) with different diameters and lengths; (2) the analysis of the dark I -V data showed the synthesized devices have rectifying behavior; (3) the analysis of the I -t data, operated at -5 V, showed that the fabricated samples have a fast-switching characteristic (approximate to 65 ms); (4) the sample with a 0.05 M concentration as the optimal layer, with the lowest light reflectance feature, has the maximum light sensitivity ( S -- I P /I D ) and responsivity ( R* ) to various visible light illuminations (460, 31 mA/W for blue, 201, 14 mA/W for green, and 190, 13 mA/W for red).