Abstract
Scalable methods for deposition of lead halide perovskite thin films are required to enable commercialization of the highly promising perovskite photovoltaics. Here, we have developed a slot-die coating process under ambient conditions for methylammonium lead iodide (MAPbI3) perovskite on heated substrates (about 90 °C on the substrate surface). Dense, highly crystalline perovskite films with large grains (100–200 μm) were obtained by careful adjustment of the deposition parameters, using solutions that are similar but more dilute than those used in typical spin-coating procedures. Without any further after treatments, such as antisolvent treatment or vapor annealing, we achieved power conversion efficiencies up of 14.5% for devices with the following structure: conducting tin oxide glass (FTO)/TiO2/MAPbI3/spiro-MeOTAD/Au. The performance was limited by the significant roughness of the deposited films, resulting from the hot-casting method, and the relatively high deposition temperature, which led to a defect-rich surface due to loss of MAI.
Highlights
Large-scale implementation of renewable energy is highly needed to reduce the carbon footprint of energy production and to meet the growing energy demand in our society today
Lead halide-based perovskite solar cell have undergone a remarkable increase in power conversion efficiency (PCE) in a short period of time, from 3.8% reported in 20092 to 25.2% in 2019,3 making this technology a serious competitor to the market dominating silicon-based photovoltaics
Deposition on a hot substrate (90 °C) provides immediate formation of a dense black crystalline perovskite film without the need for antisolvent or other after-treatments. Such hot casting of the high-boiling point precursor solutions leads to films with large perovskite crystals, but it has the disadvantage of giving high roughness in the resulting films
Summary
Large-scale implementation of renewable energy is highly needed to reduce the carbon footprint of energy production and to meet the growing energy demand in our society today. The slot-die coating process presented here can be considered to be a hot-casting method, which induces rapid perovskite crystallization Such a method has been previously used in combination with spin-coating.[7] We have used significantly higher substrate temperatures (∼90 °C) than in other reports on slot-die coating of perovskites on heated substrates where temperatures of about 65 °C were used in combination with additional air or nitrogen flow.[19,20]. The slot-die coater unit (Compact sheet coater, FOM technologies, Denmark) was placed in a fume hood; deposition took place in ambient air with a relative humidity of 40−50% In this system, the slot-die head is stationary while the hot plate carrying the substrates is moving.
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