The electronic properties of CH₃NH₃PbI₃ perovskite surfaces tuned by inverted polarities of pyridine and ethylamine

Abstract

The electronic properties of perovskite surface are remarkably affected by the polarity of absorbed pyridine.

First-Principles Study of Zinc Phthalocyanine Molecules Adsorbed on Methylammonium Lead Iodide Surfaces

“…Teng et al have demonstrated that the orientation of MA cations has profound consequences on the electronic properties of the surfaces and the PbI 2 -terminated ones generally have smaller band gaps compared with the MAI-terminated surfaces. As a result, the PbI 2 -terminated MAPbI 3 has an advantage to promote photoexcited holes transferring to the hole transport materials . Our results that the calculated band gap of the MAPbI 3 slabs are in accordance with previous calculations of MAPbI 3 − and other semiconductor materials. , Our calculated band gap (HOMO–LUMO gap) of an isolated ZnPc molecule is 1.42 eV, agreeing with the previous calculation …”

“…As a result, the PbI 2 -terminated MAPbI 3 has an advantage to promote photoexcited holes transferring to the hole transport materials. 33 Our results that the calculated band gap of the MAPbI 3 slabs are in accordance with previous calculations of MAPbI 3 33−35 and other semiconductor materials. 36,37 Our calculated band gap (HOMO−LUMO gap) of an isolated ZnPc molecule is 1.42 eV, agreeing with the previous calculation.…”

Defect Passivation by Pyridine-Carbazole Molecules for Efficient and Stable Perovskite Solar Cells

“…Molecules with a lone pair of electrons (Lewis bases) have been used. They undergo coordination bonding with under-coordinated Pb 2+ defects at the surfaces of perovskites. , Density functional theory (DFT) studies further confirmed that Lewis bases have strong coordination with under-coordinated Pb 2+ , producing a Lewis adduct. − In general, under-coordinated Pb 2+ defects are commonly observed in perovskite films because of the evaporation of organic cations and halides, generating under-coordinated Pb 2+ ions at the perovskite surface and at the grain boundaries. , Pyridine and its derivatives have been used to passivate under-coordinated Pb 2+ defects in perovskites. ,− We also reported that 4- tert butyl pyridine (4- t BP) can passivate the defects in perovskites and improve the initial performance of the PSCs . However, pyridine derivatives commonly used for defect passivation are in a liquid state and gradually evaporate over time, detrimentally impacting the stability of PSCs.…”