Image-Charge Barriers, Not Polaron Kinetics, Limit Charge Extraction at Ligand-Passivated CsPbI3 Interfaces
Year: 2026
Type: preprint
Abstract: Charge extraction across inorganic perovskite–organic ligand interfaces represents a critical materials bottleneck in perovskite optoelectronics, yet the defectindependent electrostatic origins of this process remain poorly understood. Here, we present a multiscale framework that combines first-principles density functional theory with macroscopic Scharfetter–Gummel drift-diffusion simulations to isolate and quantify this intrinsic transport barrier on CsPbI3 surfaces passivated by methylammonium (MA), butylammonium (BA), and phenethylammonium (PEA). We demonstrate that effective interfacial dielectric screening is governed by ligand orientational polarizability and adsorption geometry rather than isolated molecular polarizability, producing a counter-intuitive ordering εBA > εMA > εPEA that inverts the conventional molecular polarizability sequence. The resulting imagecharge barriers (Umax im = 202.6–229.8 meV) exceed kBT by nearly an order of magnitude, driving severe thermodynamic carrier depletion (CAF = 1.38 × 10−4–3.95 × 10−4), while all computed polaron reorganization energies (λ < 100 meV) confirm delocalized, large-polaron character—unambiguously establishing that the dominant bottleneck is electrostatic rather than kinetic. Despite its lowest electron reorganization energy (λe = 37.8 meV), PEA’s orientational locking generates the largest image-charge barrier (Umax im = 229.8 meV), whereas the conformationally flexible BA maximizes in-plane screening and reduces steady-state carrier accumulation by an order of magnitude under operational bias. Furthermore, ligand rigidity governs a structural electron–hole reorganization asymmetry (λh/λe = 0.98–1.85), establishing a defect-independent, purely structural mechanism for carrier selectivity. These findings deliver four quantitative design rules for charge-transparent passivation interlayers, replacing empirical ligand screening with a predictive framework anchored in orientational polarizability, adsorption geometry, and carrier-type symmetry. The identified image-charge barrier constitutes a Boltzmann activation energy Uim(T ) that is directly measurable via temperature-dependent photoconductance, providing an unambiguous experimental validation signature.
Source: ChemRxiv
Authors: Naveen Kumar, Anirban Mondal
Institution: Indian Institute of Technology Gandhinagar
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223408093