Optimizing CZTSe Solar Cell Architecture: Comparative Study of ZnO, TiO₂, and MoO₃ as Electron Transport Layers

This study investigates the optimization of Cu2ZnSnSe4(CZTSe)-based solar cells by employing distinct charge transport layers (CTLs) for enhancing their efficiency. ZnO, TiO2, and MoO3 are evaluated as electron transport layers (ETLs), while NiOx serves as a hole transport layer (HTL). By systematically varying ETL and CZTSe layer thicknesses, the influence of these parameters on solar cell performance is explored. According to obtained results, it has been found that the optimum size of base and emitter layers are equal to
$2 ~\mu \text{m}$
and 80 nm in n-ZnO/p-CZTSe/p-NiOx,
$1.5 ~\mu \text{m}$
and 60 nm in n-TiO2/p-CZTSe/p-NiOx, as well as
$1 ~\mu \text{m}$
and 60 nm in n-MoO3/p-CZTSe/p-NiOx. Maximum efficiencies of n-ZnO/p-CZTSe/p-NiOx, n-TiO2/p-CZTSe/p-NiOx, and n-MoO3/p-CZTSe/p-NiOx solar cells with optimal sizes are equal to 21.35%, 21.76% and 24.14%, respectively. So, MoO3 with thickness of 60 nm is the optimal ETL for CZTSe based solar cell due to forming high electric field and large electrostatic potential difference which helps to separate effectively the photogenerated electron-hole pairs. Each solar cells reached to maximum open circuit voltage at minimum base thickness and to maximum short circuit current at maximum base thickness. Furthermore, the study assesses the potential of CZTSe, a promising alternative to traditional silicon-based solar cells, as it exhibits a tunable bandgap allowing for efficient sunlight absorption. The investigation delves into the unique ETL/CZTSe/HTL structure, utilizing ZnO, TiO2, and MoO3 as ETLs and NiOx as the HTL. The results reveal that MoO3, with a thickness of 60 nm, emerges as the optimal ETL for CZTSe-based solar cells, achieving a peak efficiency of 24.14% due to its ability to create a high electric field and significant electrostatic potential difference, enhancing the effective separation of photogenerated electron-hole pairs. Additionally, the study explores the interplay between emitter and base layer thicknesses, demonstrating the impact on open circuit voltage and short circuit current, providing valuable insights for the design and optimization of CZTSe-based solar cells.