“…Among various optoelectronic systems or devices, photodetectors (PDs) have attracted essential interest for their great potential applications in many different fields, e.g., biological imaging, space detection, environment monitoring, and optical communication. , Recently, organic–inorganic hybrid perovskite MAPbX 3 (X = Cl, Br, I) nanomaterials have been observed to show promising prospect in photoelectric detectors due to their outstanding optical and electrical properties of high light absorption, tunable band gap, long diffusion length, large mobility, and low recombination rate of carriers. , Moreover, the solution processing synthesis of perovskite materials is facile and low cost, which is very suitable for sustainable and industrial production. Till now, although many different kinds of perovskite PDs (perovskite polycrystalline thin-film PD, perovskite single-crystal PD, perovskite quantum dot PD, and perovskite nanowire PD) have been successfully prepared and observed to exhibit outstanding photoresponses and broad response spectra, the devices are mainly fabricated based on the simple geometries usually with microscale working sizes, the performances are still unsatisfactory, and the modulation methods are also very limited. − To solve these issues, constructing nanometer-thick perovskite heterojunctions is considered as a promising method. , In particular, different from the single-perovskite PD, a desirable built-in field, which is beneficial to the quick transport and separation of photoexcited electron–hole pairs, is produced in the heterojunction .…”