Spray-coating is a deposition technique that is widely used in industry and could in principle be used to fabricate perovskite photovoltaic (PV) devices at low cost and high volume. As with any deposition technique, the fabrication of thin films requires optimization of a range of parameter space in order to control film uniformity and homogeneity. This is particularly important in PV fabrication as the quality of the thin film has an important effect on device efficiency. This Perspective summarizes the developments in spray-cast perovskite solar cells made over the past few years, with particular attention paid to strategies employed to control the crystallization of the perovskite. Steady progress has now been made with spray-cast perovskite PV devices recently demonstrated having a power conversion efficiency of 18.3%. We highlight trends within the research field and discuss challenges that will be necessary to drive such techniques toward practical application.

We use ultrasonic spray-coating to sequentially deposit thin films of tin oxide, a triple-cation perovskite and spiro-OMeTAD, allowing us fabricate perovskite solar cells (PSCs) with a champion reverse scan power conversion efficiency (PCE) of 19.4% on small-area substrates. We show that the use of spraydeposition permits us to rapidly (>80 mm s −1) coat 25 mm × 75 mm substrates that were divided into a series of devices each with an active area of 15.4 mm 2 , yielding an average PCE of 10.3% and a peak PCE of 16.3%. By connecting seven 15.4 mm 2 devices in parallel on a single substrate, we create a device having an effective active area of 1.08 cm 2 and a PCE of 12.7%. This work demonstrates the possibility for spray-coating to fabricate high efficiency and low-cost perovskite solar cells at speed.

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.

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.