Classification of lattice defects and the microscopic origin of p-type conductivity of Sb2Se3 solar cell absorber with varying Al2O3-layer thicknesses

Based on first-principles calculations, herein, we reveal the origin of p-type conductivity and the roles of Al and O in the enhancement of hole concentration in Sb2Se3 thin films. A new class of low-energy defects with shallow acceptor levels is presented by substituting Se with O and inducing Sb vacancy [OSe–VSb] complex. Moreover, the concentration of holes induced by the intrinsic and extrinsic defects is calculated and discussed. Our results can explain the intriguing experimental observation where the hole concentration is enhanced after Al2O3 capping and provide a new insight to the defect chemistry and physics of Sb2Se3 thin films. In addition, Al2O3 layers with varying thicknesses have been deposited on the surface of Sb2Se3 films. The crystallinity, orientation and electrical properties of Sb2Se3 films have been investigated in detail. Lastly, 6.87% efficiency of Sb2Se3 solar cells without other optimization has been obtained based on the structure of FTO/CdS (CBD)/Sb2Se3/Al2O3/Au.