High-Performance Flexible Perovskite Solar Cells by Using a Combination of Ultrasonic Spray-Coating and Low Thermal Budget Photonic Curing

Abstract

Realizing the commercialization of high-performance and robust perovskite solar cells urgently requires the development of economically scalable processing techniques. Here we report a highthroughput ultrasonic spray-coating (USC) process capable of fabricating perovskite film-based solar cells on glass substrates with power conversion efficiency (PCE) as high as 13%.Perovskite films with high uniformity, crystallinity, and surface coverage are obtained in a single step. Moreover, we report USC processing on TiO 2 /ITO-coated polyethylene terephthalate (PET) substrates to realize flexible perovskite solar cells with PCE as high as 8.1% that are robust under mechanical stress. In this case, a photonic curing technique was used to achieve a highlyconductive TiO 2 layer on flexible PET substrates for the first time. The high device performance and reliability obtained by this combination of USC processing with optical curing appears very promising for roll-to-roll manufacturing of high-efficiency, flexible perovskite solar cells. -halide perovskite solar cells, with power conversion efficiencies (PCEs) rapidly reaching circa 20%, 1-3 are one of the most promising, next-generation photovoltaic technologies due to their excellent material properties, including long carrier diffusion lengths 4 and large absorption coefficients. 5 To achieve high-quality perovskite films, a variety of deposition techniques, such as thermal evaporation, 6-8 single-step spin-coating, 9,10 layer-by-layer or two-step coating, 11,12 and vapor-assisted 13 processes have been developed. However, one major disadvantage of most laboratory-scale techniques is that they are incompatible with lowcost, roll-to-roll processing envisioned for large-scale manufacturing. Existing scalable processing techniques include ink-jet printing, slot-die coating, blade-coating, screen printing, and ultrasonic spray-coating. 14-21Among these cost-effective roll-to-roll compatible processes, ultrasonic spray-coating (USC) is one of the most promising that has been successfully exploited for the fabrication of various organic electronic devices including light emitting diodes, 22 photovoltaics, 23,24 photodetectors, 25 and field-effect transistors. 26 The overall advantage of USC is its ability to simultaneously provide high throughput, better control over directional deposition, efficient use of materials, uniform film coverage, compatibility with variety of substrates, with the potential for the deposition of continuous layers without dissolution of underlying layers. 23,[26][27][28] Recently, the USC process was demonstrated to deposit perovskite thin films on glass substrates, and the resulting devices showed an average PCE of 7. 8%. 29 However, considering the diverse application potential for thin film perovskites, it is highly important to demonstrate the fabrication of high-performance devices on light-weight and flexible substrates using scalable techniques. So far, one major challenge for the fabrication of solar cells on plastic substrates is their ...

Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology

“…The PCE and SEM images obtained (Figures 3(a) and 3(b)) prove the possibility of obtaining efficient solar cells with spray coating of the perovskite layer. A perovskite film with high uniformity, crystallinity, and surface coverage was obtained in a single step with a resulting cell PCE of 13% by Sanjib et al 36 with ultrasonic spray-coating. This, combined with optical curing of TiO x layers, led to flexible perovskite cells on polyethylene terephthalate (PET) substrates with a PCE equal to 8.2%.…”

An electron beam evaporated TiO2layer for high efficiency planar perovskite solar cells on flexible polyethylene terephthalate substrates

“…14,15,23,24 More recently, a photonic curing technique was also used to achieve TiO 2 layers at low processing temperatures on PET substrates, resulting in devices with PCE of only 8.1%. 25 In this work, …”

Defect-Free Large-Area (25 cm2) Light Absorbing Perovskite Thin Films Made by Spray Coating

“…Physical properties of the precursor solution may also affect the thin film characteristics prepared by other casting methods. Various solution concentrations (9.5-33 wt.%) [20,24,25] have been used by others as the starting concentration for the fabrication of perovskite films, but, to the best of our knowledge, this has not been done systematically. Therefore, here we measured the contact angle, surface tension and viscosity of the mixed halide perovskite MAPbI 3−x Cl x dissolved in DMF solvent in a wide range of concentrations (5-50 wt.%).…”