In　recent　years,　solution-processed　lead　trihalide　perovskites　have　been　widely　used　as　semiconductors　in　photodetectors　with　their　salient　features　of　tunable　direct　bandgap,　long　carrier　lifetime,　extended　diffusion　length,　and　high　carrier　mobility,　etc.　For　the　photodetector　application,　perovskites　with　different　structures　ranging　from　the　traditional　3D　perovskites　to　the　emerging　2D　perovskites,　to　1D　nanowires,　and　to　0D　quantum　dots,　have　been　synthesized.　In　this　perspective,　the　recent　advances　in　the　strategies　of　preparing　novel　lead　trihalide　perovskites　with　different　nanostructures　are　summarized　together　with　an　overview　on　their　application　in　photodetectors　including　photoconductors,　photodiodes,　and　phototransistors.　The　semiconductor　selection　and　structure–performance　relationships　of　various　photodetectors　over　the　past　5　years　are　discussed　comprehensively.　Finally,　a　brief　summary　as　well　as　an　in-depth　discussion　regarding　the　current　challenges　and　perspectives　for　the　future　development　of　perovskite-based　photodetectors　is　presented.　©　2020　Wiley-VCH　GmbH