Laves phases are a class of tetrahedrally close-packed Frank− Kasper phases with AB 2 stoichiometry. While these phases appear as intermetallic line compounds in a variety of metallic alloys, it is challenging to stabilize Laves phases in reconfigurable soft matter because of the substantial difference in preferred volume between the large A particles and small B particles. Surprisingly, perhaps the conceptually simplest approachblending two diblocks with incompatible core blockshas not been explored yet. Using self-consistent field theory, we predict that a Laves phase should emerge as a phase field in the eutectic phase diagram of an AB/B′C diblock copolymer blend if (i) the AB and B′C diblock copolymers are selected such that their neat melts produce bcc phases with the particle volume ratio of the desired Laves phase and (ii) the repulsion between A and C blocks is sufficiently strong to minimize mixing between micelles. This diblock "alloying" approach produces phase behavior that closely mimics that arising in intermetallic compound-producing metal alloys and should provide a relatively simple synthetic route to produce soft Frank−Kasper phases that are challenging to achieve by conventional polymer-based approaches. Article pubs.acs.org/Macromolecules

The C14 and C15 Laves phases form as micelle packing structures in many types of soft matter, but the related C36 phase, which consists of alternating C14-type and C15-type layers,...

Bismuth triiodide is a lead-free direct wide-bandgap solution-processable semiconductor that could be an alternative to lead-based perovskites in tandem or multijunction solar cells. However, the power conversion efficiency of single-junction BiI3 solar cells remains low. Here, we determine the main loss mechanisms of BiI3 solar cells in both n-i-p and p-i-n architectures. Overall, p-i-n devices have higher power conversion efficiency than that of n-i-p. It is found that n-i-p devices have higher (and significant) non-radiative recombination at the interface of the BiI3/transport layer, resulting in a lower open-circuit voltage than p-i-n devices. Moreover, the high series resistance (>70 Ω cm2) and a low average electron–hole diffusion length (∼60 nm) contributes to the low short-circuit current density (<5 mA/cm2) and fill factor (<40%) in all devices. In addition, interface recombination also reduces short-circuit current density. Finally, we demonstrate that lithium doping of BiI3 can increase the diffusion length of BiI3 to improve the performance of BiI3 solar cells. Solar cells with the configuration ITO/NiOx/Li:BiI3/PC61BM/bis-C60/LiF/Ag obtain a power conversion efficiency of 1.3% under AM 1.5 G illumination. The deep understanding of the main loss mechanisms of this work paves the way for future optimization of BiI3 solar cells.

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