Tin(IV) oxide materials have been extensively used as electron transport materials in n−i−p perovskite solar cells (PSCs) due to their superior optoelectronic properties, low-temperature processability, and high chemical stability. However, solvent incompatibility and processing temperature have limited the direct deposition of fully solution-processed SnO 2 in p− i−n devices. In this study, we overcome this limitation by the functionalization of SnO 2 nanoparticles with acetate through ligand exchange, allowing their dispersion in anhydrous ethanol. The SnO 2 dispersion was deposited on the perovskite absorber by blade coating without damaging the underlying perovskite layer, as determined by X-ray diffraction and scanning electron microscopy. Photoluminescence spectroscopy confirmed effective electron extraction. The champion device shows 14.1% initial power conversion efficiency (PCE) which is unprecedented for a p−i−n device employing solution-phase SnO 2 . PSCs stored for 40 days in a nitrogen flow box retained an average of 95.8% of the initial PCE.

Schematic illustration of custom-built roll-to-roll machine setup showing the continuous processing between the unwind and rewind stations including CDT surface preparation, deposition by slot die, drying by an air knife and thermal processing using IPL.

Solution processing of flexible perovskite solar cells (f-PSCs) provides an avenue for scalable, high-throughput printing of lightweight, scalable, and cost-effective flexible solar cells. However, the deposition of fully solution-processed metal oxide charge transport layers on perovskites has been limited by solvent incompatibilities and high processing temperatures for metal oxide nanoparticles. In this study, we present high-performance, inverted f-PSCs from the direct deposition of yttrium-doped SnO2 nanoparticles functionalized with acetate on top of perovskite as an ink in anhydrous ethanol via blade coating. Yttrium doping improved device performance by improving the charge extraction with a decreased series resistance leading to improvements in the open-circuit voltage and fill factor. The champion power conversion efficiency for 0.1 cm2 devices increased from 14.3% for undoped SnO2 to 16.5% with 2% Y:SnO2 doping, which is unprecedented for f-PSCs on ITO-PET substrates employing SnO2 as an ETL.

Perovskite solar cells (PSCs) are a promising alternative solar technology, but the technical challenges of (1) stability/durability, (2) efficiency at scale, and (3) manufacturability must be overcome to achieve widespread PSC commercialization. The challenge of balancing solution ink formulation and scalable manufacturing is often overlooked in the literature, where focus is on adopting inks from processes that will not scale. In this study, we apply a classical roll-to-roll manufacturing perspective, utilizing both compositional engineering and intense pulsed light (IPL) annealing, to develop a mixed-cation perovskite ink with a robust coating window that simultaneously solve issues of stability and manufacturability for PSCs. Our method resulted in blade-coated, flexible, mixed-cation PSCs on ITO-PET substrates with a champion power conversion efficiency (PCE) efficiency of 16.7% using IPL annealing of the absorber layer and, to our knowledge, is one of the fastest processing methods for the perovskite layer. This overall reduction in processing time with a stable ink represents an advance toward the scaled production of perovskite solar cells on flexible substrates.

A series of nickel oxide (NiO x ) inks, in the perovskite antisolvent chlorobenzene (CB) containing 15% ethanol, were prepared for the fabrication of p-i-n perovskite solar cells by blade coating. The inks included triethylamine (Et3N) and alkyl xanthate salts as ligands to disperse NiO x particle aggregates and stabilize suspension. A total of four inks were evaluated: 0X (Et3N with no alkyl xanthate), 4X (Et3N + potassium n-butyl xanthate), 12X (Et3N + potassium n-dodecyl xanthate), and 18X (Et3N + potassium n-octadecyl xanthate). The inks were characterized by UV–visible spectroscopy and FT-IR spectroscopy and the resulting films analyzed by thermogravimetry and scanning electron microscopy. Devices prepared using the 0X ink resulted in a peak power conversion efficiency (PCE) of 14.47% (0.25 cm2) and 9.96% (1 cm2). The 0X devices showed no significant loss of PCE after 100 days in a nitrogen flow box. Devices prepared with inks containing alkyl xanthate ligand had lower PCE that decreased with decreasing chain length, 18X > 12X > 4X.