Broad-Band Photodetectors Based on Copper Indium Diselenide Quantum Dots in a Methylammonium Lead Iodide Perovskite Matrix

Boosting the Performance of Organic Photodetectors with a Solution-Processed Integration Circuit toward Ubiquitous Health Monitoring

Organic photodetectors, as an emerging wearable photoplethysmographic (PPG) technology, offer exciting opportunities for next-generation photonic healthcare electronics. However, the mutual restraints among photoresponse, structure complexity, and fabrication cost have intrinsically limited the development of organic photodetectors for ubiquitous health monitoring in daily activities. Here, an effective route to dramatically boost the performance of organic photodetectors with a solution-processed integration circuit for health monitoring application is reported. Through creating an ideal metal-semiconductor junction interface that minimizes the trap states within the device, solution-printed organic field-effect transistors (OFETs) are achieved with an ultrahigh signal amplification efficiency of 37.1 S A-1 , approaching the theoretical thermionic limit. Consequently, monolithic integration of the OFET with an organic photoconductor enables the remarkable amplification of photoresponse signal-to-noise ratio by more than four orders of magnitude from 5.5 to 4.6 × 105 , which is able to meet the demand for accurately extracting physiological information from the PPG waveforms. This work offers an effective and versatile approach to greatly enhance the photodetector performance, promising to revolutionize health monitoring technologies.

Interfacial passivation of CsPbI3 quantum dots improves the performance of hole-transport-layer-free perovskite photodetectors

Photodetectors (PDs) suffer from dark current due to defects in the perovskite photosensitive layer. Contact between the photosensitive layer and carbon electrodes could result in recombination of carriers at the interface. In this work, CsPbI₃ quantum dots (QDs) were added between the photosensitive layer and the carbon electrode as the interfacial layer to passivate the surface defects of perovskite layer and improve the energy level matching at the interface. The effect of QDs concentrations on the passivation of the perovskite layer was investigated. It was found that the photoluminescence intensity of perovskite films was the strongest and the decay lifetime was the longest when the QDs concentration was 3 mg/mL. Owing to QDs passivation, the dark current of perovskite PD decreased by 94% from [Formula: see text] to [Formula: see text] A. The responsivity (R) at 605 nm improved by 27% from 0.29 to 0.37 A/W at 0 V bias voltage. The specific detectivity (D*) increased by 420% from [Formula: see text] to [Formula: see text] Jones.

Effect of transparent substrate on properties of CuInSe2 thin films prepared by chemical spray pyrolysis

In this paper, the properties of CuInSe₂ (CISe) films deposited on three transparent substrates (FTO, FTO/NiO_x, FTO/MoO₃) are studied. These substrates might be used for bifacial solar cells, in place of the conventional glass/Mo substrates. CISe layers are deposited by spray pyrolysis followed by a selenization process. For the same deposition conditions, the CISe layers on FTO show the largest grain size (~ 0.50 µm) and crystallinity, while FTO/MoO₃ substrates result in the smallest grains (~ 0.15 µm). The optical bandgap of the CISe films ranged from 1.35 eV for FTO substrate to 1.44 eV for FTO/MoO₃ substrate. All films show p-type conductivity, with the carrier densities of 1.6 × 10¹⁷ cm^-3, 5.4 × 10¹⁷ cm^-3, and 2.4 × 10¹⁹ cm^-3 for FTO, FTO/NiO_x, and FTO/MoO₃ substrates, respectively. The CISe films also show different conduction, and valence levels, based on the substrate. In all cases, an ohmic behavior is observed between the CISe and substrate. The results demonstrate that CISe layer crystallinity, carrier concentration, mobility, and energy levels are strongly dependent on the chemical nature of the substrate. Bare FTO shows the most appropriate performance in terms of device requirements.

A novel approach for designing efficient broadband photodetectors expanding from deep ultraviolet to near infrared

Broadband photodetection (PD) covering the deep ultraviolet to near-infrared (200-1000 nm) range is significant and desirable for various optoelectronic designs. Herein, we employ ultraviolet (UV) luminescent concentrators (LC), iodine-based perovskite quantum dots (PQDs), and organic bulk heterojunction (BHJ) as the UV, visible, and near-infrared (NIR) photosensitive layers, respectively, to construct a broadband heterojunction PD. Firstly, experimental and theoretical results reveal that optoelectronic properties and stability of CsPbI₃ PQDs are significantly improved through Er³⁺ doping, owing to the reduced defect density, improved charge mobility, increased formation energy, tolerance factor, etc. The narrow bandgap of CsPbI₃:Er³⁺ PQDs serves as a visible photosensitive layer of PD. Secondly, considering the matchable energy bandgap, the BHJ (BTP-4Cl: PBDB-TF) is selected as to NIR absorption layer to fabricate the hybrid structure with CsPbI₃:Er³⁺ PQDs. Thirdly, UV LC converts the UV light (200-400 nm) to visible light (400-700 nm), which is further absorbed by CsPbI₃:Er³⁺ PQDs. In contrast with other perovskites PDs and commercial Si PDs, our PD presents a relatively wide response range and high detectivity especially in UV and NIR regions (two orders of magnitude increase that of commercial Si PDs). Furthermore, the PD also demonstrates significantly enhanced air- and UV- stability, and the photocurrent of the device maintains 81.5% of the original one after 5000 cycles. This work highlights a new attempt for designing broadband PDs, which has application potential in optoelectronic devices.