Near Infrared Sensitive Organic Photodiode Utilizing Exciplex Absorption in NdPc₂/C₆₀ Heterojunction

Abstract

Organic photodiodes (OPDs) have been the subject of extensive research due to their inherent advantages of largearea detection, wide range of material selection and low-cost fabrication. Near infrared (NIR) OPDs were realized mainly by using narrow energy-gap materials and doping organic NIR dyes into the active layer. Here we report on realization of NIR OPDs by exploiting the exciplex absorption in heterojunction consisting of neodymium phthalocyanine (NdPc2) and C60. For NIR OPDs based on NdPc2/C60 planar heterojunction with C60 thickness of 50 nm, the optimal NdPc2-layer thickness for specific detectivity is 30 nm, while that for photoresponsivity is smaller than 10 nm. A maximal specific detectivity of ~4.46×10 9 Jones was obtained at the optimized NdPc2 layer thickness of 30 nm. At NdPc2 layer thickness of 10 nm, a maximal photoresponsivity of 60 mA/W and a maximal external quantum efficiency (EQE) of 17% were obtained. The results presented here demonstrate that utilizing exciplex absorption in heterojunction based on NdPc2 and C60 is a prospective route for realizing NIR OPDs.

Near‐infrared organic photoelectric materials for light‐harvesting systems: Organic photovoltaics and organic photodiodes

“…In the early stage of research, small‐molecule‐based NIR photodiodes mainly adopted thermally evaporated PHJs due to the controllability of film morphology. The focus of research was mainly on phthalocyanine‐type small molecules, such as copper‐phthalocyanine (CuPc), lead phthalocyanine (PbPc), tin phthalocyanine (SnPc), neodymium phthalocyanine (NdPc 2 ), chloroaluminum phthalocyanine (ClAlPc), and indium (III) phthalocyanine chloride (ClInPc) . In 2011, Wang et al demonstrated an organic photodetector using CuPc as electron donor and a CuPc derivative, hexadecafluoro‐copper‐phthalocyanine complex (F16CuPc), as electron acceptor .…”

Significant Detectivity Enhancement of Broad Spectral Organic–Inorganic Hybrid Photodiodes by C60 Film as Hole-Blocking Layer

“…Another important parameter characterizing photodetectors is the specific detectivity ( D *). Here we ignore the power spectral density of other noise sources such as flicker or thermal noise, it can be described as [ 40 ] where q is the elementary electric charge, J dark is the dark current density.…”

Vacuum‐Processed Small Molecule Organic Photodetectors with Low Dark Current Density and Strong Response to Near‐Infrared Wavelength

“…Specific detectivity, D*, of a photodetector determines its ability to detect the weakest photosignal under various noises such as shot, Johnson (thermal), and flicker (1/f). [12,19,22,[49][50][51][52][53][54] D* is a crucial figure of merit for photodetectors, which is usually expressed in the simple equation by [8][9][10][11][12][13][14][15][16][17][18]21,22,38,52,54,55]…”

“…[1,2] Currently, a boost in research works on OPDs have been observed after the successful commercialization of OLEDs and OPVs, since photodetectors can be widely applied in various fields such as imaging, optical communication, environmental/health monitoring, night vision, and chemical/ biological sensing. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Although OPDs show tremendous potentials, yet certain key parameters such as external quantum efficiency (EQE), linear dynamic range (LDR), and transient response should be improved significantly to optimize the detectivity so that it can vie against its inorganic counterpart. [5,14,15,[18][19][20][21][22] The EQE of an OPD device is typically expressed in percentage that reflects the number of electrons collected at the electrode per incident photon at specific wavelength, while LDR describes the maximum dynamic range of an OPD device corresponding to its linear response in relation with the variation of incident light intensities.…”