Programme

P.8 -- Posters, VCTP-51

Date: Tuesday, 4 August 2026

Time: 09:30 - 10:30

Dual-site methylammonium-zinc co-doping enhances phase stability and tunable optoelectronic properties in α-CsPbI3 perovskites: a first-principles study

Nguyen Chi Ben1, Pham Vu Nhat2 and Minh Triet Dang1

1School of Education, Can Tho University, Can Tho, Vietnam. 2Department of Chemistry, Can Tho University, Can Tho, Vietnam.

All-inorganic cesium lead iodide (CsPbI3) perovskites are promising candidates for next-generation optoelectronic devices; however, their practical implementation is hindered by the poor phase stability of the photoactive α-phase. In this work, density functional theory calculations combined with M3GNet machine-learning-assisted structural optimization were employed to investigate the effects of A-site methylammonium (MA+) doping, B-site Zn2+ doping, and synergistic (MA-Zn) co-doping on the structural, mechanical, electronic, and optical properties of α-CsPbI3. The co-doped system exhibits the highest Goldschmidt tolerance factor (t = 0.834) and a strongly negative formation energy (-4.357 eV), indicating significantly enhanced thermodynamic stability relative to pristine CsPbI3. Phonon analysis further reveals that co-doping suppresses lattice instability while preserving the soft vibrational characteristics beneficial for carrier transport. Mechanical calculations confirm that all compositions satisfy the Born stability criteria and maintain ductile behavior despite progressive lattice softening upon doping. Electronic structure analysis demonstrates effective bandgap tunability from 1.253 to 1.730 eV depending on the dopant configuration, with the (MA-Zn) co-doped system exhibiting a direct bandgap of 1.594 eV, favorable for photovoltaic applications. Projected density-of-states analysis reveals that neither MA+ nor Zn2+ introduces detrimental mid-gap trap states near the band edges. Optical calculations show that Zn doping preserves strong visible-light absorption, whereas MA incorporation induces systematic blue shifts in the dielectric response and absorption spectra. Thus, the unified co-doping strategy provides a viable route for simultaneously improving phase stability and tailoring the optoelectronic properties of CsPbI3, offering atomistic insights for the rational design of stable perovskite-based photovoltaic and light-emitting devices.

Presenter: Nguyen Chi Ben