The lack of long-term stability, the presence of toxic lead, and a low photoluminescence (PL) efficiency are the major obstacles to the commercialization of lead-halide perovskite-based optoelectronic and photovoltaic devices. Herein we report a facile ambient condition doping protocol that addresses all three issues of the CsPbX 3 perovskite nanocrystals (NCs) to a substantial extent. We show that the roomtemperature treatment of these NCs with MgX 2 results in the partial (18−23%) replacement of toxic lead, enhances the PL quantum yield of green-emitting CsPbBr 3 (to ∼100% from ∼51%) and violet-emitting CsPbCl 3 NCs (to ∼79% from ∼1%), and improves the stability under ambient conditions and in the presence of light and a polar solvent. Ultrafast pump−probe and temperature-dependent PL studies reveal that curing of the intrinsic structural disorder, introduction of some shallow energy levels close to the conduction band edge, and effective passivation of the halide deficiency contribute to the improved properties of the doped systems.

Studies on ultrafast dynamics of various photo-induced processes in perovskite nanocrystals and their composites, and insights obtained from them are presented in this review.

Among the lead halide perovskites, photoluminescence quantum yield (PLQY) of violet-emitting CsPbCl3 nanocrystals (NCs) is the lowest (<5%). This is an impediment to the development of perovskite-based materials for optical applications covering the entire visible region. While PLQY of the green- and red-emitting perovskites of this class has been raised to near-unity, achieving a similar level for violet- and blue-emitting NCs is still quite challenging. Herein, we report a novel method of simultaneously passivating the surface defects and crystal disorder of violet-emitting CsPbCl3 NCs to dramatically enhance (by a factor of ∼120) the PLQY and stability without affecting the peak wavelength (403 nm) and full-width at half-maximum (FWHM) of the photoluminescence (PL) band. We show that the addition of the correct quantity of CuCl2 during the hot-injection synthesis of CsPbCl3 NCs leads to doping of Cu+ into the NCs, which rectifies octahedral distortion of the crystal and the Cl– passivates the surface; the combined influence of the two results in huge PL enhancement. NCs emitting throughout the blue region (430-460 nm) with near-unity PLQY (92%–98%) can then be obtained by partial halide-exchange of the doped sample. Femtosecond transient absorption studies suggest suppression of the ultrafast carrier trapping process in doped NCs. The results help extending the utility of these materials in optical applications by covering the violet–blue region as well.

The C−H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH2 as the amine source under aerobic conditions and visible light irradiation. Electron‐deficient and electron‐rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc‐amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction.

Transfer of the hot charge carriers prior to their cooling to the band-edge states can enhance the efficiency of a semiconductor-based solar cell much beyond its Shockley–Queisser (SQ) limiting value. Herein, we explore transfer of hot holes from the APbBr3 nanocrystals (NCs) employing a carefully chosen molecular system, 4-mercaptophenol. Ultrafast pump–probe and fluorescence measurements indeed confirm this transfer process, whose efficiency depends on the energy content of the hole, and a maximum efficiency of ∼43% is achieved with CsPbBr3 NCs for a photoexcitation energy of ∼1.46E g (E g is the band gap of the NCs). While the estimated hot hole cooling and transfer rates are quite comparable, hole transfer from the band edge is found to be a significantly slower process. The findings of the present study suggest that exceeding the SQ efficiency of the solar cells based on the perovskites can indeed be a reality.