DEVELOPMENT OF ROLL-TO-ROLL SLOT DIE COATED PEROVSKITE SOLAR CELLS

Perovskite solar cells (PSCs) have gained a lot of attention in recent years because of their outstanding optoelectronic properties and ability to tolerate defects. Additionally, they can be produced at high throughput using solution processing techniques. It is this feature of perovskite that is leveraged in this work to show their scale up potential by R2R slot die coating.Slot die coating is a highly precise and controllable technique that can be used to coat a wide range of materials onto a variety of substrates, including flexible and rigid materials. Slot die coating is commonly used in the production of electronic devices, solar cells, and other products that require thin, uniform films of materials. First a P-I-N architecture of PSCs was developed and optimised with 4 layers slot die coated. This included the hole transport layer (PEDOT:PSS), active layer (MAPbI3), electron transport layer (PCBM), buffer layer (BCP). With 4 R2R slot die coated layer, a stabilised PCE of 12% is achieved. Further, a low toxic solvent system was used to coat the MAPbI3 and its economic benefits are discussed. Next, in efforts to replace PEDOT:PSS, PTAA hole transport layer was explored. Due to thin coating of PTAA on rough surfaces of PET-ITO, PTAA based devices resulted in high shorting. To avoid this a thin buffer layer of PEDOT:PSS on PET-ITO was slot die coated before coating PTAA. This improved the performance of the PSCs to 15.2%. Further, the role of PEDOT:PSS is characterised using AFM and XPS. Additionally, the optimization of a R2R slot die coating process for MAPbI3 was carried out on a PTAA surface. The loss of performance that occurred during the transfer from spin coating to R2R slot die coating was characterized, and multiple theories were tested to understand the cause. It was found that the poor interface between MAPbI3 and PTAA was responsible for the drop in performance. Finally, the addition of dimethyl sulfoxide (DMSO) helped to reduce the gap in performance between R2R and spin-coated MAPbI3 on PTAA hole transport layers. The presence of DMSO slowed the growth of crystal formation, leading to improved crystal orientation and improved performance of the PSCs