Abstract
We report the simplest possible method to date for fabricating robust, air-stable, sandwiched perovskite photodetectors. Unlike conventionally designed photodetectors, our proposed sandwiched structure does not require electron/hole transporting layers or expensive electrodes. We demonstrate that photocurrent and sensitivity are enhanced by an order of magnitude in the MAPbI(3)-MAPbBr(3) heterojunction compared to the homojunctions of their analogues. This simpler approach may have applications in the perovskite-only class of solar cells with the goal of scaling up towards commercialization.