Hybrid-Organic-Photodetector Containing Chemically Treated ZnMgO Layer With Promising and Reliable Detectivity, Responsivity and Low Dark Current

The glass/ITO/ZnO/ZnMgO/PEOz/PCBM/P3HT:PCBM/ CH
₃
-SAM/PEDOT:PSS/ Ag structure is used to fabricate a hybrid organic photodetector (HOP). The device operates with an optimized detectivity of 4.8 × 10
¹⁴
Hz
^1/2
/W and a responsivity of 2.63 × 10
²
A/W. ZnMgO nanorods, mostly textured (with (002) orientation) and with hexagonal morphology, are made using a post-thin-film-deposition chemo-thermal process. This process helps in passivation of trap states in ZnO. The device structure reported aids in: 1) obtaining a promising broadband UV photoresponse and 2) improvement in charge collection efficiency (J
^sc
~120 mA/cm
²
). Jsc obtained in this device is ~30 times higher than the samples that only use ZnO nanorods. The photocurrent decay is dominated by a slow process with a characteristic decay time of 198 μs. This is attributable to the presence of deep traps (less density of free carriers than a large density of trap states), indicating that the defect states in ZnO are not completely eliminated even with the chemothermal passivation step used. The PEOz and CH
₃
-SAM layers in the device contribute to a reduction in dark current, and an improvement in spectral response. The results presented here are of direct relevance to the current state of the-art in UV-HOP devices.