Impact of Thin Film Thickness on the Structural, Energetic and Optoelectronic Properties of Two-Dimensional FPEA₂(MA_n-1)Pb_nI_3n+1 Perovskites

Author(s)

Ribeiro, Israel C. ; Picoli, Felipe D. ; Moraes, Pedro Ivo R. ; Fonseca, Andre F. V. ; Oliveira, Luiz N. ; Nogueira, Ana Flavia ; Da Silva, Juarez L. F.

• Document type: Journal article
• Source: ACS APPLIED ENERGY MATERIALS; v. 8, n. 6, p. 14-pg., 2025-03-12.

Abstract

Perovskite solar cell devices, composed of solution-processed perovskite layers with thicknesses of a few hundred angstroms, represent a leading technology in thin-film photovoltaics. Here, we performed a theoretical investigation based on ab initio calculations to explore the role of perovskite thin film thickness, with the general formula FPEA(2)(MA(n-1))PbnI3n+1, where FPEA represents 4-fluorophenylethylammonium cations and n ranges from 1 to 4 layers. Our findings reveal that increasing the thickness of the inorganic layer significantly influences the structural, energetic, and optoelectronic properties. Enhanced charge transfer within the inorganic framework and stronger organic-inorganic interactions are observed as the effective charge distribution shifts with increasing thickness. Exothermic trends in adsorption and interaction energies highlight the stabilizing effects of van der Waals forces and hydrogen bonding. The PbI6-octahedra play a critical role in determining the optical activity and the formation of valence and conduction bands. Thicker films exhibit more intense absorption, emphasizing the importance of PbI6-octahedra in driving optical properties. Moreover, the work function (phi) decreases with increasing thickness due to reduced quantum confinement effects, while the nature of polar FPEA molecules induces deviations in phi, underscoring the interaction between molecular composition and thickness. Band alignment further reveals strong spin-orbit coupling effects on the conduction band minimum (CBM), influenced by charge-transfer variability from FPEA to halides. These findings provide insights into thickness-dependent properties that are essential for optimizing perovskite-based devices. (AU)

• FAPESP's process: 22/09312-4 - X-ray absorption, photoemission and time-dependent transport
• Grantee: Felipe Donizete Picoli
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/21401-7 - Multi-User Equipment approved in grant 2017/11631-2: cluster computational de alto desempenho - ENIAC
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 17/11631-2 - CINE: computational materials design based on atomistic simulations, meso-scale, multi-physics, and artificial intelligence for energy applications
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 23/10395-4 - Applying quantum dots passivation towards high-stability perovskite solar cells
• Grantee: André Felipe Vale da Fonseca
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 23/12824-0 - Catalyst Screening for Electrochemical Water Splitting based on Computational Material Design Techniques
• Grantee: Pedro Ivo Rodrigues Moraes
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 24/05637-1 - Spectral functions from ground-state DMRG computations
• Grantee: Felipe Donizete Picoli
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 17/11986-5 - Generation and storage of New Energy: bringing technological development for the country
• Grantee: Ana Flávia Nogueira
• Support Opportunities: Research Grants - Research Centers in Engineering Program