Here, it is first reported that a self‐powered photodetector based on a MoS2/CH3NH3PbI3 vertical type heterojunction, which has responsivity of 60 mAW−1 and response/recovery time of 2149/899 ms. Under bias, it exhibits a photoswitching ratio exceeding 1522, fast response/recovery time of 205/206 ms, and high photoresponsivity of 68.11 AW−1. The optoelectronic performances of the photodetector are closely related to the type of the MoS2/CH3NH3PbI3 heterojunction, which acts as a hole (electron) transport field and can effectively decrease the recombination of holes and electrons. Additionally, the MoS2/CH3NH3PbI3 planar type heterojunction is also built to compare with the vertical type in optoelectronics behavior. Due to the existence of internal field, the properties of vertical type photodetector are better than those of the planar type which also presents good performance with on/off ratio up to 1476, photoresponsivity of 28 AW−1, and response rate of 356/204 ms. These results pave a new way to form an ultrahigh performance MoS2/CH3NH3PbI3 heterojunction, hold the promise for construction of a self‐powered photodetector, and develop promising atomically thin MoS2 heterostructure device for photovoltaic and optoelectronic applications.

High-quality γ-In2Se3 thin films and a γ-In2Se3/p-Si heterojunction were prepared using pulse laser deposition (PLD).

bandgap, high carrier mobility, and the absence of dangling bonds, [8] which pave the way toward extensive applications, such as field-effect transistors (FETs), [9][10][11][12][13] stacked Van der Waals superlattices [14] and heterojunctions, [15][16][17] valleytronics, [18][19][20][21] piezotronics, [22][23][24] and novel flexible [25] and transparent electronics and optoelectronics. [26,27] In particular, single-layer WS 2 , with a direct bandgap of 1.8-2.1 eV, strong photoluminescence (PL), relatively high carrier mobility, [28] and excellent mechanical properties, renders it as a promising candidate in optoelectronic devices and flexible devices.Although a variety of nanodevices based on WS 2 nanoflakes have been fabricated for phototransistors and sensors, [29] the interface of WS 2 , an important component in devices, has been frequently ignored. The surface potential, as an important property of the interface, is rele vant to work function and Fermi level of nanomaterials, which is significant for the research of charge transport, carrier concentration, and nanodevices design. Kelvin probe force microscopy (KPFM) has been applied to detect spatial charge distribution of various materials by measuring the contact potential difference (CPD) between the tip and samples. [30] Presently some relevant works about surface potential of transition metal dichalcogenides (TMDs) have been reported intermittently. [31][32][33] However, few investigations reported the surface potential of chemical vapor deposition-grown monolayer triangular WS 2 . Furthermore, the fabrication of WS 2 and MoS 2 on Au substrates has achieved important progresses. Zhu and co-workers [34] demonstrated for the first time that the crystallography of Au foil substrates made a strong effect on the growth of monolayer MoS 2 . Zhang and co-workers [35] reported the vertical hetero structures of WS 2 /MoS 2 and MoS 2 /WS 2 by sequentially growing the two composite MX 2 monolayers on Au foils through two typical chemical vapor deposition (CVD) routes. Therefore, the study of the contact potential difference between WS 2 and Au substrates is very helpful for material preparation and device applications. Furthermore, the effect of UV laser illumination and heat treatment on surface potential has not been reported yet for CVD-grown monolayer WS 2 , which is significant for study the photo responsivity mechanism and surface state.The surface potential is relevant to work function and Fermi level of materials, which is of great significance to the research of charge transport, carrier concentration, and nanodevices design. Here the effect of UV illumination and heat treatment on the surface potential distribution of chemical vapor deposition grown monolayer WS 2 on SiO 2 /Si and Au substrates is studied statistically. The experimental observation indicates that with the increase in light intensity, the surface potential of WS 2 decreases on SiO 2 /Si substrate, while increases on Au substrate. Heat treatment is introduced to tuning the surface potentia...