Liquid-chalk painted perovskite films toward low-cost photovoltaic devices

New fabrication techniques for solution-processed organic photovoltaics are more and more desirable due to greater demand for affordable method to make large area. Different from traditional spin-coating, here, we report a new fabrication technique inspired by “liquid-chalk”. Solution can be added into liquid-chalk, and is almost all coated on the devices, while spin-coating will waste most of solution. In addition, large area could be easily achieved with it. Meanwhile, the thickness and roughness could be adjusted by optimizing speed, time of annealing and amount of the solution added. We demonstrated solar cells based on liquid-chalk-coated perovskite photoactive layer (CH3NH3PbI3) exhibit comparatively high power con-version efficiency (PCE) of 14.83% on average. A champion PCE of 16.04% was attained. Similarly, applying the method in pure inorganic system (CsPbBrI2), we also successfully fabricated devices with a highest PCE of 9.17%. The results indicate that using liquid-chalk to coat is an effective new way to fabricate perovskite solar cells, and also an ideal method to make large-area and flexible devices.