One-step P2 scribing of organometal halide perovskite solar cells by picosecond laser of visible wavelength

Abstract

Perovskite solar cells (PSC) have attracted attention by their unprecedented rise in device efficiency. However, the PSCs were mostly tested for the unit cells of small area, and it is important to upscale to solar modules. Laser scribing has great potential to this end. However, the key challenge identified in one-step P2 laser scribing is to remove film stack including the hole block layer (HBL) without damaging transparent conducing oxide (TCO) based bottom contact and thus to provide interconnecting paths with minimized contact resistance. In this study, we evaluate one-step P2 scribing performance of picosecond laser of 532 nm wavelength for mesoscopic perovskite architecture with the c-TiO2 (compact TiO2) as the HBL and fluorine doped fin oxide (FTO) as bottom contact. Despite anticipated challenge of low absorption selectivity, c-TiO2 layer could be efficiently removed without FTO damage over wide processing window enabling a self-terminating mechanism. Detailed parametric studies elucidate relevant scribing mechanisms such as layer-by-layer ablation mechanism or lift-off mechanism depending laser illumination direction. It is also revealed that the removal of c-TiO2 is triggered by ablation of upper layers, in particular, the mesoporous TiO2. Module level test is under way in conjunction with investigation of further scribing mechanisms.