Temperature-dependent electrical behaviour of pulsed laser deposited CH3NH3PbBr3 thin films for visible wavelength photodetection

We have successfully deposited CH 3 NH 3 PbBr 3 thin films using pulsed laser deposition. Thin films of 78 nm thickness were formed with grain size of 400 nm and 35 nm roughness. The photoluminescence (PL) emission peak was observed at 538 nm for all the excitation wavelengths with a decrease in the PL peak intensity with increase in the excitation wavelength. Photodetector devices having the device structure FTO/CH 3 NH 3 PbBr 3 /Ag were fabricated. The temperature-dependent current–voltage characteristics have been studied over a temperature range of 303–343 K to understand the current transport mechanisms occurring within the film. Transport characteristics were fitted to the thermionic emission equation. The ideality factor was found to decrease from 1.1 to 0.68 and the barrier height was found to increase from 0.512 to 0.545 eV with increase in temperature. The deviation of the Richardson constant from its theoretical value revealed the inhomogeneity of the barrier heights. From the modified Richardson plot using the Gaussian distribution of barrier heights, the value of the Richardson constant was obtained to be 29.1 A cm −2 K −2 . The ln I–ln V plot exhibited three regions with different slopes following the Ohmic, trap filled limit and space charge limited conduction mechanisms. Also the visible light photoresponse has been studied for the application of CH 3 NH 3 PbBr 3 thin films in visible light photodetection. The values of the responsivity, sensitivity, external quantum efficiency and specific detectivity under white light illumination of 13 mW cm −2 and − 1 V bias were found to be 117.4 A/W, 1.3, 2.65 × 10 4 % and 2.99 × 10 12 Jones, respectively.