Cu(I)-I-2,4-diaminopyrimidine Coordination Polymers with Optoelectronic Properties as a Proof of Concept for Solar Cells
Date
2021Abstract
Two coordination polymers with formulas [CuI(dapym)]n and
[Cu2I2(dapym)]n (dapym = 2,4-diaminopyrimidine) have been synthesized in
water at room temperature. According to the stoichiometry used, mono (1D)
and the two-dimensional (2D) structures can be obtained. Both are made up
of Cu2I2 double chains. Their high insolubility in the reaction medium also
makes it possible to obtain them on a nanometric scale. Their structural
flexibility and short Cu−Cu distances provoke interesting optoelectronic
properties and respond to physical stimuli such as pressure and temperature,
making them interesting for sensor applications. The experimental and
theoretical studies allow us to propose different emission mechanisms with
different behaviors despite containing the same organic ligand. These
behaviors are attributed to their structural differences. The emission spectra
versus pressure and temperature suggest competencies between different
transitions, founding critical Cu2I2 environments, i.e., symmetric in the 1D compound and asymmetric for the 2D one. The intensity
in the 2D compound’s emission increases with decreasing temperature, and this behavior can be rationalized with a structural
constriction that decreases the Cu−Cu and Cu−I distances. However, compound 1D exhibits a contrary behavior that may be
related to a change of the organic ligand’s molecular configuration. These changes imply that a more significant Π−Π interaction
counteracts the contraction in distances and angles when the temperature decreased. Also, the experimental conductivity
measurements and theoretical calculations show a semiconductor behavior. The absorption of the 1D compound in UV, its intense
emission at room temperature, and the reduction to nanometric size have allowed us to combine it homogeneously with ethyl vinyl
acetate (EVA), creating a new composite material. The external quantum efficiency of this material in a Si photovoltaic mini-module
has shown that this compound is an active species with application in solar cells since it can move the photons of the incident
radiation (UV region) to longer wavelengths.