All-self-metered solution-coating process in ambient air for the fabrication of efficient, large-area, and semitransparent perovskite solar cells

We herein report several characteristics of semitransparent perovskite solar cells (PVSCs) composed of functional layers fabricated by means of a solution-coating process of self-metered horizontal dip- (H-dip-) coating. The perovskite precursor solution used here was prepared by mixing PbI2 and CH3NH3I in anhydrous GBL and DMSO. To enhance the film-forming capabilities of the CH3NH3PbI3 perovskite PV layer, a small amount of a surfactant additive of poly(oxyethylene tridecyl ether) (PTE) was mixed with the perovskite precursor solution. Using the H-dip-coating process with PTE additives dramatically reduces the formation of film defects such as grain-boundary defects and nano-pinholes in the perovskite layers, resulting in uniform and homogeneous PV layers with smooth surface morphologies, even in ambient air. The use of H-dip-coated perovskite and other functional layers, including electron/hole collecting layers, and transparent silver nanowire electrodes resulted in good performance of the semitransparent device, with a transmittance level of 23% between 400 and 800 nm and a corresponding power conversion efficiency (PCE) of 10.2%. Furthermore, we demonstrated the feasibility of fabricating over a large area 8.5 × 8.5 cm2 in size with a high PCE of 5.6% for all-solution-processed semitransparent PVSCs even in ambient air. Our study indicates that H-dip-coated functional layers can be used to yield transparent, efficient, and large-area, solution-processable semitransparent PVSCs, thus creating a new pathway toward transparent solar cells with high photovoltaic efficiencies.