Surface engineering of nanomaterials is a promising tool towards the design of new materials for conversion of solar energy into chemical energy.
In this work, doctor blading is proposed for the fabrication of strongly-coupled QD solids from a PbS nanoink for photodetection at telecom wavelengths.
Moreover, the implementation of a wearable photonic technology directly in contact with clothes would be light-weight, comfortable, noninvasive, implantable, and inherently low cost. It attracts a strong interest for industry in this futuristic field. Indeed, according to International Data Corporation, the important growth of this technology is forecasted to grow up to 213.6 millions in 2020. [8] Nowadays, examples of commercial real-time applications include textile-based displays, [9] photovoltaics [9] or health monitoring. [9] In spite of this significant progress, wearable devices still require reduced footprint, better coupling techniques, and the integration of more complex optic/electrical functionalities to meet the performances already provided by traditional semiconductors integrated on rigid substrates.Taking into account these current limitations, metal halide perovskites(MHPs) is a promising semiconductor for flexible/wearable optoelectronic devices because of the outstanding capabilities to provide light emission, gain generation, and photodetection functionalities of polycrystalline MHPs films grown at low temperature. Indeed, MHPs demonstrated a broad range of excellent electrical and optical properties, such as long diffusion lengths, [10] high absorption cross-section, [11] high quantum yield of emission at room temperature, [12] or tunable bandgap with the composition. [13] MHPbased devices include highly efficient solar cells, [14] optical active devices, [12,13,15,16] and photodetectors. [17,18] The majority of these publications, however, use a rigid substrate to fabricate the device, being a significantly lower amount of works on MHP flexible devices with a single functionality as solar cells, [19,20] optical switch, [21] or lasing. [22] On the other hand, nanocellulose (NC) [23,24] has been probed as an ideal substrate for wearable optoelectronics. [25] This polymer is obtained from the most common biopolymer on Earth, and it consists of rigid nanocrystals that can be easily assembled into films and gel materials.NC is not only an excellent bendable, deformable and stretchable material, [26] but also exhibits very interesting properties for optoelectronics. Its advantages comprise a very high transparency in the visible, [27] tunable chiral nematic order by the surface chemistry, [28] low roughness, and extremely high gas barrier properties. [29] Nevertheless, despite these promising abilities, integration of optoelectronic devices in cellulose has been elusive, being it polyimide or polydimethylsiloxane Flexible optoelectronics has emerged as an outstanding platform to pave the road toward vanguard technology advancements. As compared to conventional rigid substrates, a flexible technology enables mechanical deformation while maintaining stable performance. The advantages include not only the development to novel applications, but also the implementation of a wearable technology directly in contact with a curved surface. Here the monolithic integration of a perovskite-based optical wave...
Control of quantum-dot (QD) surface chemistry offers a direct approach for the tuning of charge-carrier dynamics in photoconductors based on strongly coupled QD solids. We investigate the effects of altering the surface chemistry of PbS QDs in such QD solids via ligand exchange using 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The roll-to-roll compatible doctor-blade technique was used for the fabrication of the QD solid films as the photoactive component in photoconductors and field-effect phototransistors. The ligand exchange of the QD solid film with MPA yields superior device performance with higher photosensitivity and detectivity, which is due to less dark current and lower noise level as compared to ligand exchange with TBAI. In both cases, the mechanism responsible for photoconductivity is related to trap sensitization of the QD solid, in which traps are responsible of high photoconductive gain values, but slow response times under very low incident optical power (<1 pW). At medium–high incident optical powers (>100 pW), where traps are filled, both MPA- and TBAI-treated photodevices exhibit similar behavior, characterized by lower responsivity and faster response time, as limited by the mobility in the QD solid.
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