Chemical Control of the Dimensionality of the Octahedral Network of Solar Absorbers from the CuI-AgI-BiI Phase Space by Synthesis of 3D CuAgBiI.

A newly reported compound, CuAgBiI, is synthesized as powder, crystals, and thin films. The structure consists of a 3D octahedral Ag/Bi network as in spinel, but occupancy of the tetrahedral interstitials by Cu differs from those in spinel. The 3D octahedral network of CuAgBiI allows us to identify a relationship between octahedral site occupancy (composition) and octahedral motif (structure) across the whole CuI-AgI-BiI phase field, giving the ability to chemically control structural dimensionality.

Charge-Carrier Mobility and Localization in Semiconducting CuAgBiI for Photovoltaic Applications.

Lead-free silver-bismuth semiconductors have become increasingly popular materials for optoelectronic applications, building upon the success of lead halide perovskites. In these materials, charge-lattice couplings fundamentally determine charge transport, critically affecting device performance. In this study, we investigate the optoelectronic properties of the recently discovered lead-free semiconductor CuAgBiI using temperature-dependent photoluminescence, absorption, and optical-pump terahertz-probe spectroscopy.

Polarons and Charge Localization in Metal-Halide Semiconductors for Photovoltaic and Light-Emitting Devices.

Metal-halide semiconductors have shown excellent performance in optoelectronic applications such as solar cells, light-emitting diodes, and detectors. In this review the role of charge-lattice interactions and polaron formation in a wide range of these promising materials, including perovskites, double perovskites, Ruddlesden-Popper layered perovskites, nanocrystals, vacancy-ordered, and other novel structures, is summarized. The formation of Fröhlich-type "large" polarons in archetypal bulk metal-halide ABX perovskites and its dependence on A-cation, B-metal, and X-halide composition, which is now relatively well understood, are discussed.

Ultrafast Excited-State Localization in CsAgBiBr Double Perovskite.

CsAgBiBr is a promising metal halide double perovskite offering the possibility of efficient photovoltaic devices based on lead-free materials. Here, we report on the evolution of photoexcited charge carriers in CsAgBiBr using a combination of temperature-dependent photoluminescence, absorption and optical pump-terahertz probe spectroscopy. We observe rapid decays in terahertz photoconductivity transients that reveal an ultrafast, barrier-free localization of free carriers on the time scale of 1.

Highly Absorbing Lead-Free Semiconductor CuAgBiI for Photovoltaic Applications from the Quaternary CuI-AgI-BiI Phase Space.

Since the emergence of lead halide perovskites for photovoltaic research, there has been mounting effort in the search for alternative compounds with improved or complementary physical, chemical, or optoelectronic properties. Here, we report the discovery of CuAgBiI: a stable, inorganic, lead-free wide-band-gap semiconductor, well suited for use in lead-free tandem photovoltaics. We measure a very high absorption coefficient of 1.

Charge-Carrier Trapping Dynamics in Bismuth-Doped Thin Films of MAPbBr Perovskite.

Successful chemical doping of metal halide perovskites with small amounts of heterovalent metals has attracted recent research attention because of its potential to improve long-term material stability and tune absorption spectra. However, some additives have been observed to impact negatively on optoelectronic properties, highlighting the importance of understanding charge-carrier behavior in doped metal halide perovskites. Here, we present an investigation of charge-carrier trapping and conduction in films of MAPbBr perovskite chemically doped with bismuth.