CdS/PbSe Heterojunction Made via Chemical Bath Deposition and Ionic Exchange Processes to Develop Low-Cost and Scalable Devices

Abstract

Complete optoelectronic devices present major difficulties to be built by aqueous chemical deposition. In this work, a ITO/CdS/PbSe heterostructure was developed, depositing CdS over an ITO-coated substrate via a chemical bath deposition (CBD) technique. The next step involved the growth of a plumbonacrite film over CdS via CBD, where the film acted as a precursor film to be converted to PbSe via ion exchange. The characterization of each material involved in the heterostructure were as follows: the CdS thin films presented a hexagonal crystalline structure and bandgap of 2.42 eV; PbSe had a cubic structure and a bandgap of 0.34 eV. I vs. V measurements allowed the observation of the electrical behavior, which showed a change from an ohmic to diode response by applying a thermal annealing at 150 °C for 5 min. The forward bias of the diode response was in the order of 0.8 V, and the current-voltage characteristics were analyzed by using the modified Shockley model, obtaining an ideality factor of 2.47, being similar to a Schottky diode. Therefore, the reported process to synthesize an ITO/CdS/PbSe heterostructure by aqueous chemical methods was successful and could be used to develop optoelectronic devices.

Synthesis Optimization of Cadmium Carbonate Films as Potential Precursor to Produce CdSe, CdTe, and CdO Films

“…Furthermore, the vibration frequencies at 158 (ν 14 ) and 267 cm −1 (ν 13 ) are associated with the vibrational lattice modes of the CO 3 2− group bonded with cadmium [19]. The signal observed at 1714 cm −1 is related to the combination of symmetric and asymmetric internal vibrations of C-O (A 1g + E g ) [14][15][16]. On the other hand, as the deposition time increased, other vibrational modes did not appear, indicating that the growth process of the films was free from the formation of oxides or impurities.…”

“…Furthermore, the vibration frequencies at 158 (ν14) and 267 cm −1 (ν13) are associated with the vibrational lattice modes of the CO3 2− group bonded with cadmium [19]. The signal observed at 1714 cm −1 is related to the combination of symmetric and asymmetric internal vibrations of C-O (A1g + Eg) [14][15][16].…”

“…Our working group is focused on synthesizing precursor films that can carry out ion exchange in a liquid or gas phase, as an alternative to common methods while avoiding expensive reagents [2,[7][8][9]13,14]. CdCO 3 is a good candidate to be used as a cadmium precursor film, since it meets one of the main characteristics of a precursor film, which is to have an ion that can be relatively easy to remove, such as the CO 3 −2 ion that has been reported in reaction mechanisms in ion exchange [1,4], and that can be replaced by selenium, tellurium, and oxide ions to produce CdSe, CdTe, and CdO, respectively.…”