In this work, we report on the fabrication and characterization of phototransistors on the basis of solution-processed organolead triiodide (CH 3NH 3PbI 3) and mixed-halide (CH 3NH 3PbI 3− xCl x) perovskite films. However, the performance of these devices, particularly channel mobility and gate tuning, needs improvements. To date, there have been some pioneering lines of work on utilizing CH 3NH 3PbX 3 as the active component in phototransistor-type devices 27, 29, 30. Various types of semiconductors have been investigated as channel materials in phototransistors, such as Si, III–V semiconductors, ZnO, carbon nanotubes, quantum dots, organics and two-dimensional materials 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49. These hybrid perovskites can also be envisioned as good candidates for phototransistor, in which the gate bias, in addition to the incident light, is used as an additional parameter to modulate the channel transport 32, 33. Supplementary Table 1 summarizes the recent progresses on developing perovskite-based photodetectors. The properties of these emerging materials also led to photoelectronic applications, such as electrically pumped lasers, light-emitting diode/transistors and photodetectors 23, 24, 25, 26, 27, 28, 29, 30, 31. Long electron–hole diffusion lengths and carrier lifetimes have also been observed in perovskite films, indicating low recombination rates of charge carriers 21, 22. The recent successes of halide perovskites in photovoltaic technologies can be primarily ascribed to their suitable, direct bandgap with large absorption coefficients and low-cost solution-based processing, as well as their excellent transport properties 17, 18, 19, 20. In their pioneering work on field-effect transistors using hybrid perovskite (C 6H 5C 2H 4NH 3) 2SnI 4 as channels, a high on/off ratio of 10 4 and a hole mobility of 0.6 cm 2V −1s −1 were reported 16. This class of materials was first discovered by Weber nearly 36 years ago 14, and Mitzi and co-workers further revealed that halide perovskites combine the favourable carrier transport of inorganic semiconductors with the facile processing of organic materials 15. Methylammonium lead halide (CH 3NH 3PbX 3, X=halogen) perovskites have been intensively pursued as light-harvesting materials in high-performance hybrid solid-state photovoltaic devices 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13.

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