An ideal photodetector must exhibit a fast and wide tunable spectral response, be highly responsive, have low power consumption, and have a facile fabrication process. In this work, a self-powered photodetector with a graphene electrode and a perovskite photoactive layer is assembled for the first time. The graphene electrode is prepared using a solution transfer process, and the perovskite layer is prepared using a solution coating process, which makes the device low cost. Graphene can form a Schottky junction with TiO to efficiently separate/transport photogenerated excitons at the graphene/perovskite interface. Unlike the conventional photovoltaic structure, in this photodetector, both photogenerated electrons and holes are transported along the same direction to graphene, and electrons tunneled into TiO are collected by the cathode and holes transported by graphene are collected by the anode; therefore, the photodetector is self-powered. The photodetector has a broad range of detection, from 260 to 900 nm, an ultrahigh on-off ratio of 4 × 10, rapid response to light on-off (<5 ms), and a high level of detection of ∼10 Jones. The high performance is primarily due to the unique charge-transport property of graphene and strong light absorption properties of perovskite. This work suggests a new method for the production of self-powered photodetectors with high performance and low power consumption on a large scale.

The poor air and thermal stability of organic-inorganic halide perovskite solar cells have hindered their real applications. Here we report the insertion of a chemical vapor deposited graphene between the Au electrode and spiro-OMeTAD in planar perovskite solar cells to block the diffusion of air and Au into the perovskite layer, where the single layer graphene is transferred into the devices by a simple laminated process. After ageing in 45% humidity air for 96 h or thermal annealing at 80 °C for 12 h, more than 94% PCE of the devices with graphene can be maintained, which is much better than that of devices without graphene (∼57%). The improved stability of devices with the graphene layer is attributed to the reduction of carrier recombination from decomposition of the perovskite layer in air or Au doping into the perovskite layer under annealing treatment. Therefore, graphene is a promising ultra-thin barrier against air and metal diffusion, and has potential applications in photovoltaic devices, integrated circuit chips and light emitting diodes.

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Perovskite solar cells (PSCs) are promising low-cost photovoltaic technologies with high power conversion efficiency (PCE). The crystalline quality of perovskite materials is crucial to the photovoltaic performance of the PSCs. Herein, a simple approach is introduced to prepare high-quality CHNHPbI perovskite films with larger crystalline grains and longer carriers lifetime by using magnetic field to control the nucleation and crystal growth. The fabricated planar CHNHPbI solar cells have an average PCE of 17.84% and the highest PCE of 18.56% using an optimized magnetic field at 80 mT. In contrast, the PSCs fabricated without the magnetic field give an average PCE of 15.52% and the highest PCE of 16.72%. The magnetic field action produces an ordered arrangement of the perovskite ions, improving the crystallinity of the perovskite films and resulting in a higher PCE.

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