Energetics of Solvent-Based Deposition of Fullerene Derivative on the Inorganic–Organic Hybrid Lead Halide Perovskite Surface

Abstract

The elementary processes that govern particle deposition on substrates during solution processing of thin films are not well understood due to the complex interactions between solute−solvent, solute−substrate, and solvent−substrate. This study presents a fundamental step-by-step systematic analysis of the deposition of a rather complex molecule, the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), with seemingly infinite orientational configurations, on the (110) surface of methylammonium lead iodide (CH 3 NH 3 PbI 3 ) perovskite in a solvated environment. We employed the adaptive biasing force (ABF) method in conjunction with classical molecular dynamics (MD) simulations to determine the potential of mean force (PMF) and corresponding configurations of deposited PCBM in the presence of chlorobenzene (CB) and vacuum. Our calculations underscore the impact of solvent on the energetics of deposition and the resulting configurations of deposited PCBM. In the presence of solvent, the most energetically favorable configuration occurs when the carbonyl oxygen (CO) of PCBM is attached with a Pb atom of perovskite surface with the fullerene (C60) pointing away from the surface. The corresponding binding energy between PCBM and perovskite is 12.9 kcal/mol at 325 K and increases with increasing temperature. In contrast, in a vacuum, the most energetically favorable configuration occurs when both C60 moiety and the CO atom of PCBM are associated with the perovskite surface resulting in a stronger binding energy of 23.6 kcal/mol due to the absence of solvent screening. We investigated the different energetic contributions that govern the overall deposition process. In solvated systems, the deposited configurations are stabilized primarily by entropic contribution due to loss of solvent structure around both perovskite surface and PCBM during deposition.

New Fullerene Derivative as an n‐Type Material for Highly Efficient, Flexible Perovskite Solar Cells of a p‐i‐n Configuration

“…[49,50] Aggregation energies of fullerene-based systems have already been theoretically studied by several research groups adopting different computational approaches. [51,52] In the case, estimation of this energy for solid state PCBM and PCBC6 were carried out with the CP2K software version 6.1, employing a Generalised Gradient Approximation (GGA)-Perdew-Burke-Ernzerhof (PBE) functional, double-zeta valence polarized (DZVP) basis sets, and Goedecker-Teter-Hutter (GTH) Pseudo Potentials, with a cutoff on the grid of 600 Ry and Grimme VdW correction (DFT-D3) to take into account dispersion interactions. [53][54][55][56][57] Current-Voltage Characterization: Current density-voltage characterization and stabilized power output measurements were performed using a Keithley 2461 source measure unit under simulated Air Mass (AM) 1.5G irradiation (100 mA cm −2 ) using an AAA-rated solar simulator (Abet Technologies, sun 2000) calibrated against an RR-208-KG5 silicon reference cell (Abet Technologies).…”

“…[ 49,50 ] Aggregation energies of fullerene‐based systems have already been theoretically studied by several research groups adopting different computational approaches. [ 51,52 ] In the case, estimation of this energy for solid state PCBM and PCBC6 were carried out with the CP2K software version 6.1, employing a Generalised Gradient Approximation (GGA)‐Perdew‐Burke‐Ernzerhof (PBE) functional, double‐zeta valence polarized (DZVP) basis sets, and Goedecker‐Teter‐Hutter (GTH) Pseudo Potentials, with a cutoff on the grid of 600 Ry and Grimme VdW correction (DFT‐D3) to take into account dispersion interactions. [ 53–57 ]…”

Study of Structure and Electronic Properties of Heterointerfaces for Photovoltaic Applications

“…A similar observation was noted in a previous study performed with the classical MD by taking into account the solvent effect. 37,38 Further, in defect-free PbI 2 surface terminations, it can be seen that there are more numbers of shorter (<3.50 Å) I−H distances and Pb−C 60 distances compared to other interatomic distances (Table 1). Additionally, structures with a large number of relatively short (<3.50 Å) interfacial I−H distances (Supporting Information, Table S1) and the C 60 of PCBM lying close to the surface were found to have relatively lower energy.…”

“…The effect of solvents has been dealt with using the adaptive biasing force method in conjunction with classical molecular dynamics (MD) simulations in a separate communication. 38 In such cases, the solvent molecules were found to be absent around both the perovskite surface and PCBM during deposition, indicating perovskite-PCBM as a dominant interactions at the PCBM/perovskite interface. Interface models were constructed using 2 × 2 perovskite slabs containing nine layers with 408 atoms for PbI 2 and eleven layers with 552 atoms for MAI, in line with a recent computational study of the tetragonal MAPbI 3 surfaces and interfaces, 18,34,41,47,61 with the DFT-optimized lattice parameter a = b = 8.66 Å. PCBM was introduced on each slab model after optimizing by adding a vacuum region of more than 25 Å.…”

“…The structural complexity of a heterointerface, such as a perovskite/PCBM interface, is a combined effect of the perovskite surface structure and PCBM as well as the unique structural features arising while they form the interface. In the perovskite/PCBM interface, the structural morphology of PCBM and its interaction with the atomic species on the perovskite surface , have been shown to be critical. On the perovskite surface, different groups of atoms, PbI 2 or CH 3 NH 3 I, are available for bonding depending on the terminating layer of the perovskite surface .…”