Novel Mg‐ and Ga‐doped ZnO/Li‐Doped Graphene Oxide Transparent Electrode/Electron‐Transporting Layer Combinations for High‐Performance Thin‐Film Solar Cells

Abstract

Herein, a novel combination of Mg‐ and Ga‐co‐doped ZnO (MGZO)/Li‐doped graphene oxide (LGO) transparent electrode (TE)/electron‐transporting layer (ETL) has been applied for the first time in Cu2ZnSn(S,Se)4 (CZTSSe) thin‐film solar cells (TFSCs). MGZO has a wide optical spectrum with high transmittance compared to that with conventional Al‐doped ZnO (AZO), enabling additional photon harvesting, and has a low electrical resistance that increases electron collection rate. These excellent optoelectronic properties significantly improved the short‐circuit current density and fill factor of the TFSCs. Additionally, the solution‐processable alternative LGO ETL prevented plasma‐induced damage to chemical bath deposited cadmium sulfide (CdS) buffer, thereby enabling the maintenance of high‐quality junctions using a thin CdS buffer layer (≈30 nm). Interfacial engineering with LGO improved the Voc of the CZTSSe TFSCs from 466 to 502 mV. Furthermore, the tunable work function obtained through Li doping generated a more favorable band offset in CdS/LGO/MGZO interfaces, thereby, improving the electron collection. The MGZO/LGO TE/ETL combination achieved a power conversion efficiency of 10.67%, which is considerably higher than that of conventional AZO/intrinsic ZnO (8.33%).

Crown Ether-Assisted Colloidal ZnO Window Layer Engineering for Efficient Kesterite (Ag,Cu)2ZnSn(S,Se)4 Solar Cells

“…The presence of ordered lattices with minimal defects is believed to enhance photovoltaic cell performance . However, the conventional magnetron sputtering technique is usually adopted for ZnO/ITO deposition, which will cause the kesterite/CdS heterojunction region to be continuously bombarded by high-energy particles (exceeding 100 eV), thus probably disrupting the ordered lattices and inducing lattice distortion. − This type of lattice distortion has also been reported in other thin-film solar cell systems, including perovskite solar cells and GaAs solar cells, potentially leading to significant carrier recombination within the space charge region (SCR). Recently, Xin et al successfully addressed the lattice disorder issue by the heterojunction annealing technique, which resulted from elemental mixing in the chemical bath deposition (CBD) process.…”

“…To kesterite solar cells, sputtering-processed ZnO (ZnO-SP) is usually employed as a window layer to insulate the CdS buffer layer from the ITO. However, ZnO particles possessing high energy (>100 eV) can potentially damage the surface of the kesterite/CdS heterojunction in the sputtering process. , Although this phenomenon was previously reported, limited direct evidence has been investigated. In this study, scanning transmission electron microscopy (STEM) is utilized to examine the lattice morphology of the CdS/ZnO heterojunction.…”