Organolead trihalide perovskite MAPbI shows a distinctive combination of properties such as being ferroelectric and semiconducting, with ion migration effects under poling by electric fields. The combination of its ferroelectric and semiconducting nature is used to make a light harvesting, self-powered tactile sensor. This sensor interfaces ZnO nanosheets as a pressure-sensitive drain on the MAPbI film and once poled is operational for at least 72 h with just light illumination. The sensor is monolithic in structure, has linear response till 76 kPa, and is able to operate continuously as the energy harvesting mechanism is decoupled from its pressure sensing mechanism. It has a sensitivity of 0.57 kPa , which can be modulated by the strength of the poling field. The understanding of these effects in perovskite materials and their application in power source free devices are of significance to a wide array of fields where these materials are being researched and applied.
A monolith photodetector is presented that utilizes the material properties of MAPbI perovskite for self-powered operation and achieves improved stability by composting with polystyrene. The self-powered operation makes this device suitable for remote applications and in smart systems. Improved stability of more than 20 days, with performance maintained by over 80% under ambient conditions, is achieved by incorporating polystyrene without additional fabrication steps. A plain MAPbI device in comparison shows a performance degradation of 70-85% within 4 days of operation. The incorporation of polystyrene also improves the current detectivity of the device by over 70 times compared to plain perovskite.
The
instability of organic lead halide perovskites such as MAPbI3 under ambient conditions is a challenge, as it leads to degradation
in device performance and has limited their long-term application.
To address this, we use the Lewis acid nature of PbI2,
a key chemical for making MAPbI3 perovskite (and others)
for in situ cross-linking of polystyrene (PS) chains in the precursor
solution. The resulting PS–perovskite devices without any encapsulating
layer show a stable structure in ambient conditions after >1000
h
of continuous 1.0 sun (AM 1.5G) illumination in air (relative humidity
of 40–50%) at 45 °C, while also showing a slightly improved
device performance. The stability is the result of the direct specific
interaction between the polymer and the perovskite that reduces ion
migration, charge recombination, trap-state density, and dark currents
and at the same time leads to improve mobility and carrier lifetime.
The interaction between the polymer and PbI2 also improves
the crystallization kinetics, leading to larger grain size in the
perovskite films. The cumulative effect of these improvements makes
the reported polymer–perovskite hybrids well suited for long-term
device applications and presents a new avenue for making stable polymer–perovskite
composites.
A commodity-scale polymer is used for controlling the nucleation and growth of single crystals of organolead halide perovskite. The polymer [polystyrene (PS)] cross-links and strongly interacts with PbI 2 and MAI (MAPbI 3 perovskite precursors) resulting in the control of the crystallization process. The PS concentration modulates the nucleation time, crystal size, and the number of perovskite single crystals. In addition, the PS-based MAPbI 3 crystals show an enhanced performance as well as improved thermal and environmental stability. Specifically, the PS-MAPbI 3 crystals show 3 times higher photocurrent than plain MAPbI 3 crystals and maintain a stable structure for more than 50 days (1200 h) under continuous 0.1 sun illumination in the air with a relative humidity of 40−45%. The improved performance and stability are attributed to the direct interaction between the PS and perovskite, which greatly reduces the ion migration, defect traps, and charge recombination and improves the carrier mobility and lifetime.
Cu 2 S and CdS nanoparticles due to their unique band character, high extinction coefficients and impact ionization effects are the most promising light absorbers for solar cells. Here Cu 2 S and CdS nanoparticles are prepared by wet chemical method and are characterized using UV-Vis Absorption Spectroscopy and X-ray Diffraction. The thin film of Cu 2 S/CdS is prepared using Spin Coating technique. Cu 2 S/CdS solar cells form a p-n heterojunction solar cells with CdS having energy gap of 4.4eV and Cu 2 S having an energy gap of 2.65 eV. The results are quite appreciable and 10.9% efficiency is obtained from Cu 2 S/CdS thin-film solar cell. The photovoltaic properties including I-V characteristics, short-circuit current (I sc), open-circuit voltage (V oc), fill factor (ff), efficiency (η) of Cu 2 S/CdS heterojunction cells have been examined.
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