The recent development of phase transfer ligand exchange methods for PbS quantum dots (QD) has enhanced the performance of quantum dots solar cells and greatly simplified the complexity of film ...deposition. However, the dispersions of PbS QDs (inks) used for film fabrication often suffer from colloidal instability, which hinders large-scale solar cell production. In addition, the wasteful spin-coating method is still the main technique for the deposition of QD layer in solar cells. Here, we report a strategy for scalable solar cell fabrication from highly stable PbS QD inks. By dispersing PbS QDs capped with CH3NH3PbI3 in 2,6-difluoropyridine (DFP), we obtained inks that are colloidally stable for more than 3 months. Furthermore, we demonstrated that DFP yields stable dispersions even of large diameter PbS QDs, which are of great practical relevance owing to the extended coverage of the near-infrared region. The optimization of blade-coating deposition of DFP-based inks enabled the fabrication of PbS QD solar cells with power conversion efficiencies of up to 8.7%. It is important to underline that this performance is commensurate with the devices made by spin coating of inks with the same ligands. A good shelf life-time of these inks manifests itself in the comparatively high photovoltaic efficiency of 5.8% obtained with inks stored for more than 120 days.
A comprehensive study unveiling the impact of heterovalent doping with Bi3+ on the structural, semiconductive, and photoluminescent properties of a single crystal of lead halide perovskites ...(CH3NH3PbBr3) is presented. As indicated by single‐crystal XRD, a perfect cubic structure in Bi3+‐doped CH3NH3PbBr3 crystals is maintained in association with a slight lattice contraction. Time‐resolved and power‐dependent photoluminescence (PL) spectroscopy illustrates a progressively quenched PL of visible emission, alongside the appearance of a new PL signal in the near‐infrared (NIR) regime, which is likely to be due to energy transfer to the Bi sites. These optical characteristics indicate the role of Bi3+ dopants as nonradiative recombination centers, which explains the observed transition from bimolecular recombination in pristine CH3NH3PbBr3 to a dominant trap‐assisted monomolecular recombination with Bi3+ doping. Electrically, it is found that the mobility in pristine perovskite crystals can be boosted with a low Bi3+ concentration, which may be related to a trap‐filling mechanism. Aided by temperature (T)‐dependent measurements, two temperature regimes are observed in association with different activation energies (Ea) for electrical conductivity. The reduction of Ea at lower T may be ascribed to suppression of ionic conduction induced by doping. The modified electrical properties and NIR emission with the control of Bi3+ concentration shed light on the opportunity to apply heterovalent doping of perovskite single crystals for NIR optoelectronic applications.
Infiltrating single crystals: Heterovalent doping with Bi3+ (see figure) leads to modulation of the charge carrier mobility and thermal activation energy of electrical conductivity in CH3NH3PbBr3 single crystals. Upon doping, a new photoluminescent emission appears in the near‐infrared region of the spectrum.
3D trench silicon pixel sensors, recently developed by the TimeSPOT collaboration, have shown excellent performance in terms of spatial resolution, timing precision and detection efficiency. The ...combination of these three features make them one of the best candidate for inner tracking detectors operating in high luminosity hadron colliders experiments. This article presents systematic characterisations of these devices made with minimum ionising particles on irradiated sensors with neutrons up to 2.5 ⋅ 10 16 1 MeV n eq cm −2 . The results show that 3D trench pixels have extremely high resistance to radiation. The measured time resolution and the detection efficiency of irradiated sensors match those of non-irradiated ones if a slightly higher bias voltage, few tens of Volts, is applied to the pixels. As of today, 3D trench pixels are the only sensors capable of achieving 10 ps time resolution after being irradiated at extremely high fluences, extending by far the capabilities of future tracking systems of HEP experiments operating under extreme conditions.
Transport layers are of outmost importance for thin‐film solar cells, determining not only their efficiency but also their stability. To bring one of these thin‐film technologies toward mass ...production, many factors besides efficiency and stability become important, including the ease of deposition in a scalable manner and the cost of the different material's layers. Herein, highly efficient organic solar cells (OSCs), in the inverted structure (n‐i‐p), are demonstrated by using as electron transport layer (ETL) tin oxide (SnO2) deposited by atomic layer deposition (ALD). ALD is an industrial grade technique which can be applied at the wafer level and also in a roll‐to‐roll configuration. A champion power conversion efficiency (PCE) of 17.26% and a record fill factor (FF) of 79% are shown by PM6:L8‐BO OSCs when using ALD‐SnO2 as ETL. These devices outperform solar cells with SnO2 nanoparticles casted from solution (PCE 16.03%, FF 74%) and also those utilizing the more common sol–gel ZnO (PCE 16.84%, FF 77%). The outstanding results are attributed to a reduced charge carrier recombination at the interface between the ALD‐SnO2 film and the active layer. Furthermore, a higher stability under illumination is demonstrated for the devices with ALD‐SnO2 in comparison with those utilizing ZnO.
Tin oxide as electron transport layer in organic solar cells (OSCs) can promote high device performance and stability. However, the poor quality of the material and of the interface with the organic layer often limits its potential. This work demonstrates that high‐quality tin oxide can be grown by atomic layer deposition, for the fabrication of OSCs with outstanding performance.
For the next generation of vertex detectors, the accurate measurement of the charged particle timing at the pixel level is considered to be the ultimate solution in experiments operating at very high ...instantaneous luminosities. This work shows that the 55 μm × 55 µm wide 150 µm thick 3D trench-type pixels, developed by the TimeSPOT Collaboration, achieve a time resolution close to 10 ps with minimum ionizing particles while maintaining a detection efficiency close to 100% when operated at a tilt angle larger than 10° from normal incidence. This record performance is obtained with software-based constant-fraction algorithms applied to signal waveforms. However, time resolutions as good as 25 ps can be achieved using a simple leading-edge discriminating technique, without any amplitude correction. Similar timing performances can also be achieved when the charged particles cross two nearby pixels if both signal amplitudes are measured. 3D trench-type pixels, as of today, are the fastest charged-particles pixel detectors available and represent a very promising solution for the future upgrade of tracking systems of many HEP experiments operating in extreme conditions.
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