Multifunctional keplerate-type polyoxometalate-organic polymer composite films for interface engineering in perovskite photodetectors

Interfacial contact and morphology control are vital to obtain high performance planar-structure perovskite photodetcetors. The substrates where the perovskite film covered are expected to direct the growth of perovskite crystal and possess suitable energy level to accept the photoelecctrons effectively. Here we firstly modify the substrate via interface engineering by using W 72 V 30 -polyethyleneimine (PEI) multifunctional interlayer . With the incorporation of W 72 V 30 , the optimized morphology perovskite films are formed by controlling the crystallization kinetics of perovskite with fewer trap states. Simultaneously, the transfer of photoelectrons become more efficient due to the better energy level alignment between W 72 V 30 and perovskite. Besides, rich animo group of the exposed PEI provide the interlayer with wetting property, resulting in a better interfacial contact between substrate and perovskite films. As a result, the photodetectors possess high-quality perovskite film and fewer electron recombinations at the surfaces and interfaces. The photodetectors reveal that the photocurrent increase from 4.5 μA to 9.1 μA, the on/off ratio is 3.99 × 10 3 and the photoresponsivity is 6.02 mA W −1 under simulated AM 1.5 illumination. The study on W 72 V 30 -PEI composite film provides not only a promising multifunctional material for interface engineering but also a facile method to reduce trap states on perovskite surface. The W 72 V 30 -PEI interlayer is formed by LBL method that could optimize the function of each component at the nanometer level. The multifunctional interlayer with good wetting property could separate the carriers effectively and direct the growth of perovskite crystals. The performance of perovskite-based photodetcetor is promoted by introducing the with W 72 V 30 -PEI interlayer. ● The multifunctional W 72 V 30 -PEI composite films served as interlayer were fabricated via a facile method. ● High nuclear W 72 V 30 might act as Lewis base to control perovskite crystallization kinetics. ● W 72 V 30 with suitable energy level could act as the bridge for electron transfer. ● The existence of PEI enables the better contact between perovskite and substrate.