Cluster-assembled CdO polymorph: A semiconductor with high carrier mobility and superior optical performance

Abstract

Using the magic cluster Cd8O8 and a C linker, we constructed a new CdO polymorph, Tet-CdO, via bottom-up assembly. Tet-CdO exhibits good mechanical, thermal, and dynamical stability, with a B1-to-Tet transition at ∼322 K or −5.3 GPa, offering a viable synthetic route. With an optimal direct bandgap of 1.58 eV (HSE06), high absorption, low reflection, and high carrier mobility (up to 13.2 × 103 cm2 V−1 s−1), Tet-CdO achieves a theoretical photoconversion efficiency of 30.8%. A pronounced electron–hole mobility imbalance causes space charge accumulation and fill factor reduction; this can be mitigated by limiting the active layer thickness to 134–949 nm. Additionally, Tet-CdO exhibits inherently weak thermal dissipation, so device thinning, high-thermal-conductivity substrates, or active cooling are needed to suppress heat buildup. These findings establish Tet-CdO as a promising next-generation photovoltaic material.