Au nanoclusters, as a quasi-zero-dimensional semiconductor fluorescent material with excellent luminescence and photostability, have been widely used in the field of bioimaging. The material also has a wide range of application prospects in electroluminescent devices as well as displays. This study proposes a novel ligand engineering strategy employing thermally activated delayed fluorescence (TADF) mechanisms to significantly improve the photoluminescent performance of Au nanoclusters (Au NCs). The proposed methodology focuses on the efficient harvesting of triplet excitons, which effectively inhibits non-radiative transition pathways. Ultra-small core-shell structured TPA-DCPP/TOAB/AuCs nanoclusters (CS-AuCs) with a size of (1.97±0.31) nm which exhibits thermally activated delayed fluorescence (TADF) were successfully synthesized via ligand engineering. Subsequently, the electronic energy level structure, exciton dynamics, and transition mechanisms were analyzed through the absorption and emission spectra of CS-AuCs via a combined analysis of temperature-dependent absorption/emission spectra and transient photoluminescence (TRPL) measurements. The results show that the short-wavelength fluorescence peaks (507 nm and 528 nm) of CS-AuCs exhibit TADF characteristics, i.e., their luminescence intensity is enhanced with increasing temperature. The CS-AuCs thin film demonstrated a maximum fluorescence peak intensity enhancement of 5.10-fold@80 ℃. The long-wavelength emission peak(797 nm), on the other hand, exhibits the temperature-dependent property of normal fluorescence peaks, i.e., the luminescence intensity decreases with increasing temperature. Meanwhile, the film-forming experiments demonstrated that CS-AuCs has excellent compatibility and film-forming properties while maintaining the fluorescence characteristics, which enhances the potential of Au nanoclusters for applications in display devices such as cluster light emitting diodes (CLED).