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(NO3)2.6 H2O) 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 (≈ 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 (SIP/ID) 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).