Improvement of CsPbBr3 photodetector performance by tuning the morphology with PMMA additive

The optoelectrical properties of semiconductor devices are strongly related to the film morphology. Here, we found that, for CsPbBr3 thin films prepared by spray coating, the addition of polymethyl methacrylate (PMMA) can completely eliminate voids and greatly reduce the surface roughness of the as-deposited films. As a consequence, the optoelectronic properties of the photodetectors fabricated as a simple vertical structure of Au/CsPbBr3(PMMA)/ITO can be improved. With the addition of PMMA, the dark current of the photodetector is reduced at least four times, and the photodetector exhibits a favourable optical response. With the illumination ranging from 400 to 510 nm, the calculated responsivity varies from 3.70 to 5.20 A/W. A good response speed with a rise time of 6.6 ms and a decay time of 11.3 ms can be achieved. Moreover, unlike the inorganic-organic hybrid perovskite detectors, this inorganic perovskite photodetector without encapsulation shows a favourable stability with a decay of 20% after 40 days under ambient air at 20% humidity.