Three-dimensional
perovskite AMX3 has great potential
in photoelectric applications, but the poor stability is a major problem
that restricts its practical application. The emergence of lower dimensional
perovskite solves this problem. Here, we have synthesized a group
of novel low-dimensional perovskites with diverse structures. Different
amino acids were incorporated in the perovskite cage. The formulas
of the compounds are (A′)
m
PbI
m+2 (A′ = COOH(CH2)
n
NH2, n = 1, 3,
5, 7, 9). These families of materials demonstrate structure-related
stability, tunable bandgap, and different photoluminescence. Single-crystal
X-ray diffraction indicated that the five materials employ different
structure types varying from edge-sharing structures to face- and
corner-sharing Pb/I structures by adjusting the number of C atoms
in organic cations, and the level of [PbI6]4– octahedral distortion was also identified. The film prepared using
these materials with longer carbon chains (n = 5,
7, 9) showed better stability, and they did not decompose within one
year at 75% RH, 40 °C. The bifunctional organic ions containing
carboxyl groups as spacer cations will form additional hydrogen bonding
between perovskite layers, resulting in higher stability of the material.
The band gaps of these materials vary from 2.19 to 2.6 eV depending
on the octahedral connection mode and [PbI6]4– octahedral distortion level, density functional theory calculations
(DFT) are consistent with our experimental trends and suggest that
the face-sharing structure has the maximum band gap due to its flatter
electron band structure. Bright green fluorescence was observed in
(COOH(CH2)7NH3)2PbI4 and (COOH(CH2)9NH3)2PbI4 when excited by 365 nm UV light. A thorough
comprehension of the structure–property relationships is of
great significance for further practical applications of perovskites.