Surface and Bulk Defect Passivation in MAPbI ₃ Perovskites with Daminozide: Effects on Carrier Dynamics and Mobility

Abstract Metal halide perovskite semiconductors are highly valued for their outstanding optoelectronic properties. However, the high density of intrinsic defect states in their polycrystalline thin films on the surface and within the bulk poses a significant challenge by diminishing carrier mobility and lifetime, thus hindering device performance. This study reveals a previously unidentified mid‐IR emissive trapping state in MAPbI ₃ that differs from conventional Shockley‐Read‐Hall (SRH) defects, exhibiting unique surface‐localized characteristics detectable through transient mid‐IR spectroscopy. A dual‐function passivation strategy using daminozide (DA) is developed, where the interlayer selectively passivates mid‐IR‐active surface defects while the additive mitigates bulk SRH defects through carbonyl‐Pb ² ⁺ coordination. This passivation strategy yields remarkable improvements in carrier dynamics, increasing diffusion constants from 0.135 to 0.165 cm ² s⁻¹ and significantly enhancing the device performance, including open‐circuit voltage and power conversion efficiency. These findings highlight the crucial importance of addressing both surface and bulk defects to optimize the optoelectronic properties of perovskites.