We use ultrasonic spray-coating to fabricate caesium containing triple-cation perovskite solar cells having a power conversion efficiency up to 17.8%. Our fabrication route involves a brief exposure of the partially wet spray-cast films to a coarse-vacuum; a process that is used to control film crystallisation. We show that films that are not vacuum exposed are relatively rough and inhomogeneous, while vacuum exposed films are smooth and consist of small and densely-packed perovskite crystals. The process techniques developed here represent a step towards a scalable and industrially compatible manufacturing process capable of creating stable and high-performance perovskite solar cells.

An encapsulation system comprising of a UV‐curable epoxy, a solution processed polymer interlayer, and a glass cover‐slip, is used to increase the stability of methylammonium lead triiodide (CH3NH3PbI3) perovskite planar inverted architecture photovoltaic (PV) devices. It is found this encapsulation system acts as an efficient barrier to extrinsic degradation processes (ingress of moisture and oxygen), and that the polymer acts as a barrier that protects the PV device from the epoxy before it is fully cured. This results in devices that maintain 80% of their initial power conversion efficiency after 1000 h of AM1.5 irradiation. Such devices are used as a benchmark and are compared with devices having initially enhanced efficiency as a result of a solvent annealing process. It is found that such solvent‐annealed devices undergo enhanced burn‐in and have a reduced long‐term efficiency, a result demonstrating that initially enhanced device efficiency does not necessarily result in long‐term stability.

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Metal–organic framework nanosheets (MONs) are incorporated into the active layer of bulk heterojunction polymer–fullerene solar cells for the first time, resulting in an almost doubling of power conversion efficiency.

Back-contact PSCs are fabricated by depositing charge-selective electrodes and MAPbI3 into micron-sized polymeric grooves, micro-modules are formed by serially-connecting grooves.