Ultrafast and broadband photodetectors based on a perovskite/organic bulk heterojunction for large-dynamic-range imaging

Abstract

Organic-inorganic hybrid perovskite (OIHP) photodetectors that simultaneously achieve an ultrafast response and high sensitivity in the near-infrared (NIR) region are prerequisites for expanding current monitoring, imaging, and optical communication capbilities. Herein, we demonstrate photodetectors constructed by OIHP and an organic bulk heterojunction (BHJ) consisting of a low-bandgap nonfullerene and polymer, which achieve broadband response spectra up to 1 μm with a highest external quantum efficiency of approximately 54% at 850 nm, an ultrafast response speed of 5.6 ns and a linear dynamic range (LDR) of 191 dB. High sensitivity, ultrafast speed and a large LDR are preeminent prerequisites for the practical application of photodetectors. Encouragingly, due to the high-dynamicrange imaging capacity, high-quality visible-NIR actual imaging is achieved by employing the OIHP photodetectors. We believe that state-of-the-art OIHP photodetectors can accelerate the translation of solution-processed photodetector applications from the laboratory to the imaging market.

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

“…Meanwhile, the photocurrent density gets saturated at high illumination due to the direct recombination of free carriers (bimolecular recombination), which governs the limit of the upper dynamic range ( Figure S5, Supporting Information). [5,14,19] Based on Equation (5), the LDR values exhibited by the OPD devices under this study are higher compared to ClInPc (77.2 dB) which is a similar derivative of ClAlPc as well as other organic-based OPDs from previous reports [31] and considerably similar to organic-inorganic hybrid perovskite photodetectors (191 dB), [56] notwithstanding lower than inorganic Si photodetectors (200-240 dB). [17] The performance of the OPD device was further investigated by studying the frequency response and transient photovoltage.…”

“…The response of the OPD device under various intensities of light was studied by measuring the linear dynamic range (LDR), which is expressed as the ratio of the strongest to the weakest optical power (irradiance) when the device maintains its linear response. [20,49] Figure 7 depicts the LDR plots of the OPD devices which are exposed to radiance from laser and LED at a bias voltage of −2 V. The LDR (dB) of OPD device was calculated by using Equation (5) [5,14,15,[20][21][22]31,52,55,56] J J…”

“…The frequency bandwidth of the OPD device was estimated by measuring the cut-off frequency (f −3dB ) at the signal strength of −3dB under continuous illumination. [14,15,20] Fundamentally, f −3dB of an OPD device is expressed in terms of the transport time of charge carriers and the time constant (RC) following Equation (6) [5,[20][21][22]56] f…”

Advances in perovskite photodetectors

“…Another strategy to broaden the spectrum is the combination of perovskite and organic semiconductor. 15 Narrow bandgap conjugated polymers, as commercially available materials, can absorb the light from UV to NIR region significantly. By combining polymer with perovskite as the photosensitive layer together, a highly sensitive broadband photodetector can be structured.…”

Enhanced Performance of Perovskite Single-Crystal Photodiodes by Epitaxial Hole Blocking Layer

“…The noise current ( I n ) of the epitaxial device under −100 V is measured as 1.12 × 10 −10 A Hz −1/2 approximately. Based on the I n and R , the specific detectivity ( D * ) of the epitaxial device could be obtained by the following equations (Li et al, 2020 ):…”