Colloidal lead-free perovskite nanocrystals have recently received extensive attention because of their facile synthesis, the outstanding size-tunable optoelectronic properties, and less or no toxicity in their commercial applications. Tin (Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions. Here, we propose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals, demonstrating the role of Ge 2+ in stabilizing Sn 2+ cation while enhancing the optical and photophysical properties. The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies, reducing the surface traps and leading to a longer excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices show the highest efficiency of 4.9 %, enhanced by nearly 60 % compared to that of pure Sn nanocrystals-based devices.

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The doping of halide perovskite nanocrystals (NCs) with manganese cations (Mn2+) has recently enabled enhanced stability, novel optical properties, and modulated charge carrier dynamics of the NCs host. However, the influence of Mn doping on the synthetic routes and the band structures of the host has not yet been elucidated. Herein, it is demonstrated that Mn doping promotes a facile, safe, and low‐hazard path toward the synthesis of ternary Cs3Bi2I9 NCs by effectively inhibiting the impurity phase (i.e., CsI) resulting from the decomposition of the intermediate Cs3BiI6 product. Furthermore, it is observed that the deepening of the valence band level of the host NCs upon doping at Mn concentration levels varying from 0 to 18.5% (atomic ratio) with respect to the Bi content. As a result, the corresponding Mn‐doped NCs solar cells show a higher open‐circuit voltage and longer electron lifetime than those employing the undoped perovskite NCs. This work opens new insights on the role of Mn doping in the synthetic route and optoelectronic properties of lead‐free halide perovskite NCs for still unexplored applications.

In this study, a gel/liquid interface is utilized for growing a new (calcium‐phosphate)/carrageenan garden. The hydrogels are made from carrageenan loaded with either sodium phosphate or calcium chloride, while the interfaced solution contains a source of the salt not used in the hydrogels (i. e. the sodium‐phosphate hydrogel with the calcium‐chloride solution and vice versa). The physical and chemical properties of tubes grown from both systems of the same amount of carrageenan have been reported. Interestingly, when varying the amounts of carrageenan (and thus controlling the stiffness of the phosphate‐hydrogel system), it is possible to control the thickness and height of the tubes.

Colloidal lead-free perovskiten anocrystals have recently received extensive attention because of their facile synthesis,t he outstanding size-tunable optoelectronic properties,and less or no toxicity in their commercial applications. Tin(Sn) has so far led to the most efficient lead-free solar cells, yet showing highly unstable characteristics in ambient conditions.H ere,w ep ropose the synthesis of all-inorganic mixture Sn-Ge perovskite nanocrystals,demonstrating the role of Ge 2+ in stabilizing Sn 2+ cation while enhancing the optical and photophysical properties.The partial replacement of Sn atoms by Ge atoms in the nanostructures effectively fills the high density of Sn vacancies,reducing the surface traps and leading to alonger excitonic lifetime and increased photoluminescence quantum yield. The resultant Sn-Ge nanocrystals-based devices showthe highest efficiency of 4.9 %, enhanced by nearly 60 %compared to that of pure Sn nanocrystals-based devices.

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In this work, we measure the hole mobility in the model polymer system poly(3-hexylthiophene-2,5-diyl) by using different measurement techniques. Our main purpose is to determine how the recently developed charge extraction by a linearly increasing voltage technique for metal–insulator–metal devices (MIM-CELIV) compares to other commonly used methods, such as space charge limited currents and time-of-flight. Our findings suggest that the MIM-CELIV technique gives a slightly lower mobility than the other techniques, which is understandable given that the method measures the mobility of relaxed charge carriers in the dark unlike, for example, time-of-flight where charge carriers are photogenerated. In addition, we scrutinize the accuracy and reliability of the techniques used, showing that differences in mobility smaller than a factor of two are not detectable unless statistics from many devices are available.

The recently introduced perovskite solar cell (PSC) technology is a promising candidate for providing low-cost energy for future demands. However, one major concern with the technology can be traced back to morphological defects in the electron selective layer (ESL), which deteriorates the solar cell performance. Pinholes in the ESL may lead to an increased surface recombination rate for holes, if the perovskite absorber layer is in contact with the fluorine-doped tin oxide (FTO) substrate via the pinholes. In this work, we used sol-gel-derived mesoporous TiO2 thin films prepared by block co-polymer templating in combination with dip coating as a model system for investigating the effect of ESL pinholes on the photovoltaic performance of planar heterojunction PSCs. We studied TiO2 films with different porosities and film thicknesses, and observed that the induced pinholes only had a minor impact on the device performance. This suggests that having narrow pinholes with a diameter of about 10 nm in the ESL is in fact not detrimental for the device performance and can even, to some extent improve their performance. A probable reason for this is that the narrow pores in the ordered structure do not allow the perovskite crystals to form interconnected pathways to the underlying FTO substrate. However, for ultrathin (~20 nm) porous layers, an incomplete ESL surface coverage of the FTO layer will further deteriorate the device performance.