Peter Armstrong1,Sashil Chapagain1,Siva Chandra Sekhar Pakanati1,Thad L Druffel1,Craig Grapperhaus1
University of Louisville1
Peter Armstrong1,Sashil Chapagain1,Siva Chandra Sekhar Pakanati1,Thad L Druffel1,Craig Grapperhaus1
University of Louisville1
State of the art perovskite solar cells (PSCs) have reached record efficiencies on laboratory scale systems. However, transitioning to large scale fabrication of PSCs is still a work in progress. A part of the next steps necessary for upscaling the fabrication of PSCs is the demonstration of uniform charge transport layers, such as metal oxides, at scale. NiOx is a popular inorganic hole transport material for upscaling as it is easy to produce at scale, is environmentally stable and has been highly successful in small scale systems. Large area deposition of NiOx nanoparticles has been demonstrated at slow speeds of 5 mm/s by blade coating from aqueous solutions. Increasing deposition speeds to 10 mm/s or 30 mm/s requires the addition of a surfactant to improve surface wetting and film uniformity. The addition of traditional surfactants such as cetrimonium bromide or triton X-100 has been observed to obstruct charge extraction when low temperature annealing is used. Herein, we demonstrate that the addition of short chain alcohols such as isopropanol and tert-butanol effectively improve surface wetting while not interfering with charge extraction when followed by low temperature annealing. Additionally, uniform films were able to be deposited at 2 m/min by blade coating and roll-to-roll slot die coating on ITO coated PET substrates. Changes in zeta potential, surface tension, film uniformity, and power conversion efficiency were quantified as a function of alcohol concentration to identify key traits necessary for high quality film deposition. Films deposited using the optimized solution composition showed improved fill factor, open circuit potential, power conversion efficiency compared to solutions without the alcohols present.