Enhancing performance of phthalocyanine-based short-wave infrared photomultiplication organic photodetectors through interface engineering (<italic>invited</italic>)

ObjectiveHigh sensitivity short-wave infrared organic photodetectors are of great importance for applications in communications, medicine, and environmental monitoring. MoO3 is widely used as a hole transport layer in organic photodetectors due to its excellent hole-transport properties. However, the presence of metal and oxygen vacancies degrades device performance. To address this issue, we successfully developed an organic photodetector with high sensitivity and broad spectral responsivity using an interface engineering strategy. The device employs phthalocyanine-based small molecules, PbPc and C60, as the active layer, with an ultrathin Al2O3 interface modification layer inserted between the MoO3 HTL and the active layer. The experimental results demonstrate that the introduction of interface layer effectively passivates the defects on the MoO3 surface, reduces film roughness, and suppresses the dark current density while maintaining the light current density. After optimization, with HTL and interfacial layer thicknesses of 6 nm and 1.2 nm, respectively, the device achieves its best performance: the dark current density at –10 V bias is as low as 1.5×10–6 A/cm 2, the EQE at 850 nm wavelength is as high as 4.2×104%, R is 275.3 A/W, and D* is 9.96×1013 Jones. Furthermore, the optimized device exhibits a high photocurrent on/off ratio across the ultraviolet–visible–short-wave infrared spectrum. This work provides an effective interface control strategy for the development of high-performance organic photodetectors.MethodsIn order to develop high-performance SWIR PM-OPDs, a HTL was incorporated, and an Al2O3 interface layer was inserted different positions within the HTL to optimize device performance. The Al2O3 interface layer effectively passivates defects in the MoO3 HTL, leading to improved film quality and morphology. Consequently, the device maintains a higher light current density while reducing the dark current density.Results and DiscussionsThe experimental results establish the MoO3/Al2O3 configuration as the optimal device architecture. This structure reduces the dark current density from 9.3×10–3 A/cm2 to 1.5×10–6 under 660 nm illumination of 660 nm at a bias voltage of –10 V, while maintaining a high light current density. Consequently, the device achieves a maximum light-dark current density ratio of 368 at –10 V (Fig.2(c), (d)). AFM characterization revealed that the surface roughness of the MoO3 film significantly decreased after the introduction of a 1.2 nm Al2O3 interface modification layer, demonstrating that the Al2O3 modification effectively suppresses the formation of metal and oxygen vacancies in the MoO3 film, improves the quality of the film, and is more conducive to improving the photoelectric performance of the device (Fig.2(e), (f)). Further thickness optimization revealed that the device exhibits optimal performance with a HTL thickness of 6 nm and an interface layer thickness of 1.2 nm. Ultimately, the J-V curve and transient response curve confirmed that the structure still had a resolvable switch ratio at 1310 nm wavelength, demonstrating its broad-spectrum detection ability (Fig.4).ConclusionsIn this work, the ratio of light-dark current density of SWIR PM-OPDs with sandwich structure was significantly enhanced by introducing a HTL and inserting an Al2O3 interlayer at various positions within the HTL. The thickness of HTL and Al2O3 interface layer were further optimized. It was found that the device exhibited the optimal light-dark current density ratio when the MoO3 HTL and Al2O3 interface modified layer were 6 nm and 1.2 nm thick, respectively. AFM analysis confirmed that the Al2O3 interlayer effectively improves the film quality of the HTL, reducing the dark current density of the device to 1.5×10−6 A/cm2 at –10 V bias. The optimal EQE, R and D* of the device are 4.2×104 %, 275.3 A/W and 9.96×1013 Jones at 850 nm and –10 V bias, respectively. This work provides an effective strategy for developing high-performance PM-OPDs with broad spectral response.