Solution-processed organo-lead halide perovskites are produced with sharp, color-pure electroluminescence that can be tuned from blue to green region of visible spectrum (425–570 nm). This was accomplished by controlling the halide composition of CH3NH3Pb(BrxCl1–x)3 [0 ≤ x ≤ 1] perovskites. The bandgap and lattice parameters change monotonically with composition. The films possess remarkably sharp band edges and a clean bandgap, with a single optically active phase. These chloride–bromide perovskites can potentially be used in optoelectronic devices like solar cells and light emitting diodes (LEDs). Here we demonstrate high color-purity, tunable LEDs with narrow emission full width at half maxima (FWHM) and low turn on voltages using thin-films of these perovskite materials, including a blue CH3NH3PbCl3 perovskite LED with a narrow emission FWHM of 5 nm.

Self-assembled hybrid perovskite quantum wells have attracted attention due to their tunable emission properties, ease of fabrication, and device integration. However, the dynamics of excitons in these materials, especially how they couple to phonons, remains an open question. Here, we investigate two widely used materials, namely, butylammonium lead iodide (CH(CH)NH)PbI and hexylammonium lead iodide (CH(CH)NH)PbI, both of which exhibit broad photoluminescence tails at room temperature. We performed femtosecond vibrational spectroscopy to obtain a real-time picture of the exciton-phonon interaction and directly identified the vibrational modes that couple to excitons. We show that the choice of the organic cation controls which vibrational modes the exciton couples to. In butylammonium lead iodide, excitons dominantly couple to a 100 cm phonon mode, whereas in hexylammonium lead iodide, excitons interact with phonons with frequencies of 88 and 137 cm. Using the determined optical phonon energies, we analyzed photoluminescence broadening mechanisms. At low temperatures (<100 K), the broadening is due to acoustic phonon scattering, whereas at high temperatures, LO phonon-exciton coupling is the dominant mechanism. Our results help explain the broad photoluminescence line shape observed in hybrid perovskite quantum wells and provide insights into the mechanism of exciton-phonon coupling in these materials.

Emerging autonomous electronic devices require increasingly compact energy generation and storage solutions. Merging these two functionalities in a single device would significantly increase their volumetric performance, however this is challenging due to material and manufacturing incompatibilities between energy harvesting and storage materials. Here we demonstrate that organic-inorganic hybrid perovskites can both generate and store energy in a rechargeable device termed a photobattery. This photobattery relies on highly photoactive two-dimensional lead halide perovskites to simultaneously achieve photocharging and Li-ion storage. Integrating these functionalities provides simple autonomous power solutions while retaining capacities of up to 100 mAh/g and efficiencies similar to electrodes using a mixture of batteries and solar materials.

Strong interest exists in the development of organic-inorganic lead halide perovskite photovoltaics and of photoelectrochemical (PEC) tandem absorber systems for solar fuel production. However, their scalability and durability have long been limiting factors. In this work, we reveal how both fields can be seamlessly merged together, to obtain scalable, bias-free solar water splitting tandem devices. For this purpose, state-of-the-art cesium formamidinium methylammonium (CsFAMA) triple cation mixed halide perovskite photovoltaic cells with a nickel oxide (NiO x) hole transport layer are employed to produce Field's metal-epoxy encapsulated photocathodes. Their stability (up to 7 h), photocurrent density (-12.1±0.3 mA cm −2 at 0 V vs. RHE) and reproducibility enables a matching combination with robust BiVO 4 photoanodes, resulting in 0.25 cm 2 PEC tandems with an excellent stability of up to 20 h and a bias-free solar-to-hydrogen efficiency of 0.35±0.14%. The high reliability of the fabrication procedures allows scaling of the devices up to 10 cm 2 , with a slight decrease in bias-free photocurrent density from 0.39±0.15 mA cm −2 to 0.23±0.10 mA cm −2 due to an increasing series resistance. To characterise these devices, a versatile 3D-printed PEC cell was also developed. The modular PEC cell represents an affordable alternative to existing designs and can be easily adjusted for a broad range of samples. Overall, these findings shed further light on the factors required to bring both perovskite photovoltaics and photoelectrocatalysis into large-scale applications, revealing some key aspects for device fabrication, operation and implementation.

Spin exchange and charge transfer interactions between molecules and lanthanide-doped nanoparticles allow for unprecedented control of dark triplet excitons.