article published yes Niraj Nitish Patil author Ruiqi Wu author Christine Fiedler author bd3fceba-dc74-11ea-a0a7-c17f71817366 Nilotpal Kapuria author Bingfei Nan author Navita Navita author 6ebe278d-ba0b-11ee-8184-f34cdc671de40000-0001-7408-8197 Andreu Cabot author Maria Ibáñez author 43C61214-F248-11E8-B48F-1D18A9856A870000-0001-5013-2843 Kevin M. Ryan author Alex M. Ganose author Shalini Singh author MaIb department GradSch department HighTE: The Werner Siemens Laboratory for the High Throughput Discovery of Semiconductors for Waste Heat Recovery project Copper chalcogenides offer high charge mobility and low lattice thermal conductivity but suffer from structural instability due to dynamic Cu+ migration. Here, we report a colloidal hot-injection synthesis of ternary cesium copper selenide (CsCu5Se3) nanocrystals (NCs), achieving precise control over phase, size, and morphology through tailored precursor-ligand modulation. This strategy enabled systematic exploration of stable and metastable Cs–Cu–Se phases and mechanistic investigation of nucleation and growth, providing insight into phase modulation and dimensional control at the nanoscale. CsCu5Se3 NCs exhibit low lattice thermal conductivity (∼0.5 Wm–1K–1) and an experimental zT of 0.27 at 718 K. Complementary first-principles calculations, consistent with experimental electronic and optical responses, predict a zT of 1.05 at 1000 K. These findings elucidate the formation dynamics of CsCu5Se3 and establish ABZ (A = alkali, B = metal, Z = chalcogen) NCs as tunable platforms for advanced functional applications. American Chemical Society2026 eng 2380-819510.1021/acsenergylett.5c02909 111481-488 Patil, Niraj Nitish, Ruiqi Wu, Christine Fiedler, Nilotpal Kapuria, Bingfei Nan, Navita Jakhar, Andreu Cabot, et al. “Layered Alkali-Copper Selenides: Deciphering Thermoelectric Properties and Reaction Pathways for Nanostructuring β-CsCu5Se3.” <i>ACS Energy Letters</i>. American Chemical Society, 2026. <a href="https://doi.org/10.1021/acsenergylett.5c02909">https://doi.org/10.1021/acsenergylett.5c02909</a>. Patil NN, Wu R, Fiedler C, Kapuria N, Nan B, Jakhar N, Cabot A, Ibáñez M, Ryan KM, Ganose AM, Singh S. 2026. Layered alkali-copper selenides: Deciphering thermoelectric properties and reaction pathways for nanostructuring β-CsCu5Se3. ACS Energy Letters. 11(1), 481–488. N.N. Patil, R. Wu, C. Fiedler, N. Kapuria, B. Nan, N. Jakhar, A. Cabot, M. Ibáñez, K.M. Ryan, A.M. Ganose, S. Singh, ACS Energy Letters 11 (2026) 481–488. Patil, Niraj Nitish, et al. “Layered Alkali-Copper Selenides: Deciphering Thermoelectric Properties and Reaction Pathways for Nanostructuring β-CsCu5Se3.” <i>ACS Energy Letters</i>, vol. 11, no. 1, American Chemical Society, 2026, pp. 481–88, doi:<a href="https://doi.org/10.1021/acsenergylett.5c02909">10.1021/acsenergylett.5c02909</a>. Patil, N. N., Wu, R., Fiedler, C., Kapuria, N., Nan, B., Jakhar, N., … Singh, S. (2026). Layered alkali-copper selenides: Deciphering thermoelectric properties and reaction pathways for nanostructuring β-CsCu5Se3. <i>ACS Energy Letters</i>. American Chemical Society. <a href="https://doi.org/10.1021/acsenergylett.5c02909">https://doi.org/10.1021/acsenergylett.5c02909</a> N. N. Patil <i>et al.</i>, “Layered alkali-copper selenides: Deciphering thermoelectric properties and reaction pathways for nanostructuring β-CsCu5Se3,” <i>ACS Energy Letters</i>, vol. 11, no. 1. American Chemical Society, pp. 481–488, 2026. Patil NN, Wu R, Fiedler C, et al. Layered alkali-copper selenides: Deciphering thermoelectric properties and reaction pathways for nanostructuring β-CsCu5Se3. <i>ACS Energy Letters</i>. 2026;11(1):481-488. doi:<a href="https://doi.org/10.1021/acsenergylett.5c02909">10.1021/acsenergylett.5c02909</a> 210012026-01-18T23:02:43Z2026-01-19T08:43:21Z