Pentacoordinated Organotin(IV) Complexes as an Alternative in the Design of Highly Efficient Optoelectronic and Photovoltaic Devices: Synthesis and Photophysical Characterization

Abstract

The synthesis of four pentacoordinated organotin(IV) complexes prepared in a one-pot reaction from 2-hydroxy-1-naphthaldehyde, 2-amino-3-hydroxypyridine and organotin oxides is reported. The complexes were characterized by UV-Vis, IR, MS, ¹H, ¹³C and ¹¹⁹Sn NMR techniques. The compound based on 2,2-diphenyl-6-aza-1,3-dioxa-2-stannanaphtho[1,2-h]pyrido[3,2-d]cyclononene revealed the formation of a monomeric complex with a distorted five-coordinated molecular geometry intermediate between the trigonal bipyramidal and square pyramidal. In order to find possible applications in photovoltaic devices, hybrid films of organotin(IV) complexes embedded in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with graphene were deposited. The topographic and mechanical properties were examined. The film with the complex integrated into the cyclohexyl substituent has high plastic deformation, with a maximum stress of 1.69 × 10⁷ Pa and a Knoop hardness of 0.061. The lowest values of 1.85 eV for the onset gap and 3.53 eV for the energy gap were obtained for the heterostructure having the complex with the phenyl substituent. Bulk heterojunction devices were fabricated; these devices showed ohmic behavior at low voltages and a space-charge-limited current (SCLC) conduction mechanism at higher voltages. A value of 0.02 A was found for the maximum carried current. The SCLC mechanism suggests hole mobility values of between 2.62 × 10^-2 and 3.63 cm²/V^.s and concentrations of thermally excited holes between 2.96 × 10¹⁸ and 4.38 × 10¹⁸ m^-3.

Keywords: PEDOT:PSS; electrical properties; graphene; hybrid film; optical properties; organotin(IV) complexes; organotin–Schiff bases; pentacoordinated organotin.

Scheme 1

Synthetic strategy for the production of organotin(IV) complexes.

Figure 1

Molecular structure of compound 1c.

Figure 2

One-dimensional polymeric chain formed by C-H···N (blue dots) interactions in 1c (symmetry code: i 3/4-x,-1/4+y,-1/4+z).

Figure 3

Electronic absorption spectra of 1a–1d recorded in methanol at a concentration of 2.04530 × 10⁻⁵ M.

Figure 4

Simultaneous TGA–DSC curves of the thermal decomposition of pentacoordinated organotin(IV) complexes 1a–1d, under flowing dry N₂ (50 mL·min⁻¹) and at a heating rate of 10 °C·min⁻¹.

Figure 5

AFM topography of PEDOT:PSS-graphene-organotin(IV) films.

Figure 6

(a) Transmittance spectra, (b) absorption coefficient spectra and (c) Tauc plots of hybrid films.

Figure 7

Device schematics.

Figure 8

I–V curves from ITO/PEDOT:PSS-graphene-organotin(IV) complex/Ag devices under different lighting conditions.