CdS/ZnS Bilayer Thin Films Used As Buffer Layer in 10%-Efficient Cu₂ZnSnSe₄ Solar Cells

Abstract

This work deals with the soda-lime glass/Mo/Cu2ZnSnSe4/CdS/ZnS/i-ZnO/ITO solar cells. CdS/ZnS bilayers were synthesized by chemical bath deposition (CBD) method as buffer layers for Cu2ZnSnSe4 (CZTSe) solar cells. The depositions were carried out by varying the deposition time of the CdS film, while keeping the deposition time of the ZnS film constant. The devices went from 7.2% efficiency in a reference device using CdS to 10% in a device including a thin film of ZnS. All devices were processed without any additional annealing treatment on CdS/ZnS layers. J–V, EQE, SEM, Raman, and C–V characterizations were performed to investigate the properties of the solar cells as a function of the thickness of the CdS layer and to shed light on the origin of influence of the ZnS layer to the device performance. Moreover, the influence of physical properties of the buffer bilayers on the electrical parameters of the solar cells are discussed by means of numerical simulation.

Sulfate-Functionalized Core–Shell ZnO/CdS/Ag2S Nanorod Arrays with Dual-Charge-Transfer Channels for Enhanced Photoelectrochemical Performance

“…Among these strategies, selecting a suitable semiconductor to form a heterojunction with ZnO is a relatively effective way to improve the light-absorption region and enhance the charge-transportation efficiency resulting from the built-in electric field. CdS is considered an ideal semiconductor to construct a heterojunction with ZnO on account of the narrow band gap (2.4 eV) for high visible-light absorption and suitable band position for catalysis. , However, it is well known that CdS-based photoelectrodes suffer from photocorrosion originating from hole-driven oxidation reactions, resulting in their short durability . In general, introducing hole-transfer channels by decorating surface cocatalysts, such as metal-based semiconductors or hydroxides, − is capable of suppressing photocorrosion.…”

“…CdS is considered an ideal semiconductor to construct a heterojunction with ZnO on account of the narrow band gap (2.4 eV) for high visible-light absorption and suitable band position for catalysis. 19,20 However, it is well known that CdS-based photoelectrodes suffer from photocorrosion originating from hole-driven oxidation reactions, resulting in their short durability. 21 In general, introducing hole-transfer channels by decorating surface cocatalysts, such as metal-based semiconductors or hydroxides, 22−24 is capable of suppressing photocorrosion.…”

Stability of Cu2ZnSnSe4/CdS heterojunction based solar cells under soft post-deposition thermal treatments

“…The sample was finalized through the deposition of the top layers:  CdS deposition: CdS buffer layer deposited by chemical bath deposition (CBD) with a slow growth rate (~1 nm/min in average) which ensures a homogeneous and compact coverage of the absorber layer and a high reproducibility (full details of the process can be found in Ref. [40]).  Front contact deposition: i-ZnO (50 nm)/ITO (200 nm) front contact deposited by pulsed DC-magnetron sputtering (Alliance Concept CT100) with no intentional substrate heating.…”

“…The Raman scattering measurements were performed under a 442 nm excitation wavelength which is close to resonant conditions for the CdS compound [40,67]. This allows to detect both the first and second order of the LO peak (LO components of A1 and E1 symmetry modes), as can be clearly observed in the results of the analysis plotted in Figure 7 (as in the previous cases, the spectra of the 56 devices are displayed as a pale diffuse spectral cloud curve and the average spectrum is shown as a legible solid line).…”

Ecofriendly and low cost CZTS absorber layer deposited by sol-gel for solar cell applications: Effect of copper concentration on physical properties

“…In addition, ZnS is considered to be an earth-abundant and non-toxic material, which is bene cial for the nal solar cell. Some reaserchers have used CdS as a buffer layer in the nal structure of CZTS solar cell, while this latter is not considered clean and ecofriendly as CdS is a toxic layer, This variation in the buffer layers could be due to the critical importance of the density of the interfacial states, which increases with the increase in the CdS layer thickness and results a decrease in the solar cell performance [42,44].…”