The high efficiency represents an achieved goal for perovskite solar cells (PSC). The so-called carbon PSC (C-PSC) is one of the most cost-effective architecture because it is fully printable, stable for more than a year¹, and does not require expensive materials such as spiro-OMeTAD and gold. The preparation occurs on a conductive glass substrate with compact titania layer, followed by mesoporous layers of titania, zirconia and carbon applied via low-cost screen printing. Perovskite is then infiltrated into the device stack². The efficiency and the cost of large area modules, however, do not depend only on the efficiency and cost of the relative small device. In fact, the substrate surface needs to be filled with active material to properly exploit the substrate and maximise the energy production. The ratio between the photovoltaic active area and total area required to make a device is called geometric fill factor (g-FF). Examples of series-connected modules with the C-PSCs have been already reported in the literature. However, the g-FF is less than 50%¹. The reported modules are based on an accurate registration of each layer to connect cells on the same substrate in series using precision printing. This method, however, requires a loss of space to properly overlap each layer. The scribing method, by contrast, significantly reduces the lost space allowing much higher g-FF. Chemical mapping of the scribe can confirm complete material removal ensuring that the next layer can be applied appropriately³.

In this work, we propose C-PSCs in series-connected modules prepared by the scribing method. Modules from 62 to 80% g-FF were studied. Laser etching or mechanical removal were utilised and adjusted to avoid damaging of the underlying conducting layer. For the mechanical scribing method, the material removal occurred with an automated X-Y stage. The interconnections were characterized in terms of morphology and chemical composition by Raman mapping and SEM/EDX (Scanning electron microscopy with energy dispersive X-ray spectroscopy), showing the possibility to pattern the compact titania layer. The interspace between cells was changed to study the effect of the contact area between top and bottom photoelectrodes of two adjacent cells. A systematic study to optimise the interconnection distance in terms of performance and g-FF will be presented.

REFERENCE
1. G.Grancini et al, Nat. Commun., 2017, 8, 15684

2. S.Meroni et al, Sci. Technol. Adv. Mater., 2018, 19, 1-9

3. K.Hooper et al, Phys. Chem. Chem. Phys., 2017, 19, 5246