@article{gwalani_martin_kautz_guo_lambeets_olszta_battu_malakar_yang_guo_et al._2024, title={Mechanistic understanding of speciated oxide growth in high entropy alloys}, volume={15}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-024-49243-8}, abstractNote={Complex multi-element alloys are gaining prominence for structural applications, supplementing steels, and superalloys. Understanding the impact of each element on alloy surfaces due to oxidation is vital in maintaining material integrity. This study investigates oxidation mechanisms in these alloys using a model five-element equiatomic CoCrFeNiMn alloy, in a controlled oxygen environment. The oxidation-induced surface changes correlate with each element's interactive tendencies with the environment, guided by thermodynamics. Initial oxidation stages follow atomic size and redox potential, with the latter becoming dominant over time, causing composition inversion. The study employs in-situ atom probe tomography, transmission electron microscopy, and X-ray absorption near-edge structure techniques to elucidate the oxidation process and surface oxide structure evolution. Our findings deconvolute the mechanism for compositional and structural changes in the oxide film and will pave the way for a predictive design of complex alloys with improved resistance to oxidation under extreme conditions.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Gwalani, Bharat and Martin, Andrew and Kautz, Elizabeth and Guo, Boyu and Lambeets, S. V. and Olszta, Matthew and Battu, Anil Krishna and Malakar, Aniruddha and Yang, Feipeng and Guo, Jinghua and et al.}, year={2024}, month={Jun} }
 @article{mcandrews_ahmad_guo_kaczaral_amassian_rolston_mcgehee_2024, title={Why Perovskite Thermal Stress is Unaffected by Thin Contact Layers}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202400764}, DOI={10.1002/aenm.202400764}, abstractNote={Abstract Metal halide perovskite photovoltaics have emerged as a high efficiency, low‐cost alternative that can potentially rival or enhance conventional silicon technology. Despite exceptional initial power conversion efficiencies, achieving compliance with international standards and widespread adoption requires further enhancements to their operational stability. Notably, addressing mechanical strain and stress in brittle perovskites has emerged as a pivotal approach to mitigate chemical degradation and improve reliability during thermal cycling. In this study, a popularized strain engineering strategy is investigated in which a high coefficient of thermal expansion (CTE) hole transport layer (i.e., PDCBT) is cast onto inorganic perovskite (CsPbI 2 Br) at 100 °C. Contrary to previously published results, the X‐ray diffraction (XRD):Sin 2 ψ and substrate curvature measurement techniques show that the hole transport layer has no discernible impact on perovskite strain. The accuracy of the XRD:Sin 2 ψ method for measuring strain is highlighted in contrast to an analysis based on shifts of single XRD peaks which can be influenced by multiple artifacts. The findings in this study are in accordance with mechanics theory: thin layers are unable to induce significant strain changes in perovskite thin films as the force they apply is negligible compared to that applied by a thick and stiff substrate.}, journal={ADVANCED ENERGY MATERIALS}, author={McAndrews, Gabriel R. and Ahmad, Muneeza and Guo, Boyu and Kaczaral, Samantha C. and Amassian, Aram and Rolston, Nicholas and McGehee, Michael D.}, year={2024}, month={Jun} }
 @article{guo_chauhan_woodward_mcandrews_thapa_lefler_li_wang_darabi_mcgehee_et al._2023, title={<i>In situ</i> Stress Monitoring Reveals Tension and Wrinkling Evolutions during Halide Perovskite Film Formation}, volume={9}, ISSN={["2380-8195"]}, DOI={10.1021/acsenergylett.3c02079}, abstractNote={Metal halide perovskites (MHPs) are promising candidates for next-generation thin film photovoltaics and high-performance tandems. Solution-processed MHP films are susceptible to residual stress that can induce undesirable surface wrinkles. However, the origins and evolution of stress during solution processing remain elusive. In this work, we utilize multimodal in situ characterizations, including substrate curvature, reflectance, absorbance, and photoluminescence, to monitor stress and morphology evolution during MHP film formation. A film formation model emerges, consisting of a perovskite top crust on a semirigid sol with the ability to transfer mechanical forces. The phase transformation induces tension in the MHP crust, while shrinkage of the sol causes additional compression and surface wrinkles. Wrinkle-free films are formed through dynamically balancing forces between the crust and the sol. This study provides a powerful toolkit for the fast-growing area of stress engineering in MHP photovoltaics to achieve dynamic control of film stress and surface morphology.}, number={1}, journal={ACS ENERGY LETTERS}, author={Guo, Boyu and Chauhan, Mihirsinh and Woodward, Nathaniel R. and McAndrews, Gabriel R. and Thapa, Gaurab J. and Lefler, Benjamin M. and Li, Ruipeng and Wang, Tonghui and Darabi, Kasra and McGehee, Michael D. and et al.}, year={2023}, month={Dec}, pages={75–84} }
 @article{ghasemi_guo_darabi_wang_wang_huang_lefler_taussig_chauhan_baucom_et al._2023, title={A multiscale ion diffusion framework sheds light on the diffusion-stability-hysteresis nexus in metal halide perovskites}, ISSN={["1476-4660"]}, DOI={10.1038/s41563-023-01488-2}, abstractNote={Stability and current-voltage hysteresis stand as major obstacles to the commercialization of metal halide perovskites. Both phenomena have been associated with ion migration, with anecdotal evidence that stable devices yield low hysteresis. However, the underlying mechanisms of the complex stability-hysteresis link remain elusive. Here we present a multiscale diffusion framework that describes vacancy-mediated halide diffusion in polycrystalline metal halide perovskites, differentiating fast grain boundary diffusivity from volume diffusivity that is two to four orders of magnitude slower. Our results reveal an inverse relationship between the activation energies of grain boundary and volume diffusions, such that stable metal halide perovskites exhibiting smaller volume diffusivities are associated with larger grain boundary diffusivities and reduced hysteresis. The elucidation of multiscale halide diffusion in metal halide perovskites reveals complex inner couplings between ion migration in the volume of grains versus grain boundaries, which in turn can predict the stability and hysteresis of metal halide perovskites, providing a clearer path to addressing the outstanding challenges of the field.}, journal={NATURE MATERIALS}, author={Ghasemi, Masoud and Guo, Boyu and Darabi, Kasra and Wang, Tonghui and Wang, Kai and Huang, Chiung-Wei and Lefler, Benjamin M. and Taussig, Laine and Chauhan, Mihirsinh and Baucom, Garrett and et al.}, year={2023}, month={Feb} }
 @article{wang_li_ardekani_serrano-lujan_wang_ramezani_wilmington_chauhan_epps_darabi_et al._2023, title={Sustainable materials acceleration platform reveals stable and efficient wide-bandgap metal halide perovskite alloys}, volume={6}, ISSN={["2590-2385"]}, DOI={10.1016/j.matt.2023.06.040}, abstractNote={<h2>Summary</h2> The vast chemical space of emerging semiconductors, like metal halide perovskites, and their varied requirements for semiconductor applications have rendered trial-and-error environmentally unsustainable. In this work, we demonstrate RoboMapper, a materials acceleration platform (MAP), that achieves 10-fold research acceleration by formulating and palletizing semiconductors on a chip, thereby allowing high-throughput (HT) measurements to generate quantitative structure-property relationships (QSPRs) considerably more efficiently and sustainably. We leverage the RoboMapper to construct QSPR maps for the mixed ion FA<sub>1−y</sub>Cs<sub>y</sub>Pb(I<sub>1−x</sub>Br<sub>x</sub>)<sub>3</sub> halide perovskite in terms of structure, bandgap, and photostability with respect to its composition. We identify wide-bandgap alloys suitable for perovskite-Si hybrid tandem solar cells exhibiting a pure cubic perovskite phase with favorable defect chemistry while achieving superior stability at the target bandgap of ∼1.7 eV. RoboMapper's palletization strategy reduces environmental impacts of data generation in materials research by more than an order of magnitude, paving the way for sustainable data-driven materials research.}, number={9}, journal={MATTER}, author={Wang, Tonghui and Li, Ruipeng and Ardekani, Hossein and Serrano-Lujan, Lucia and Wang, Jiantao and Ramezani, Mahdi and Wilmington, Ryan and Chauhan, Mihirsinh and Epps, Robert W. and Darabi, Kasra and et al.}, year={2023}, month={Sep}, pages={2963–2986} }
 @article{zhang_darabi_nia_krishna_ahlawat_guo_almalki_su_ren_bolnykh_et al._2022, title={A universal co-solvent dilution strategy enables facile and cost-effective fabrication of perovskite photovoltaics}, volume={13}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/s41467-021-27740-4}, DOI={10.1038/s41467-021-27740-4}, abstractNote={Abstract}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Zhang, Hong and Darabi, Kasra and Nia, Narges Yaghoobi and Krishna, Anurag and Ahlawat, Paramvir and Guo, Boyu and Almalki, Masaud Hassan S. and Su, Tzu-Sen and Ren, Dan and Bolnykh, Viacheslav and et al.}, year={2022}, month={Jan} }