Bi2O2Se thin film could be one of the promising material candidates for the next-generation electronic and optoelectronic applications.However,the performance of Bi2O2Se thin film-based device is not fully explored in the photodetecting area.Considering the fact that the electrical properties such as carrier mobility,work function,and energy band structure of Bi2O2Se are thickness-dependent,the in-plane Bi2O2Se homojunctions consisting of layers with different thicknesses are successfully synthesized by the chemical vapor deposition (CVD) method across the terraces on the mica substrates,where terraces are created in the mica surface layer peeling off process.In this way,effective inteal electrical fields are built up along the Bi2O2Se homojunctions,exhibiting diode-like rectification behavior with an on/off ratio of 102,what is more,thus obtained photodetectors possess highly sensitive and ultrafast features,with a maximum photoresponsivity of 2.5 A/W and a lifetime of 4.8 μs.Comparing with the Bi2O2Se uniform thin films,the photo-electric conversion efficiency is greatly improved for the in-plane homojunctions.