Photonic Curing of Nickel Oxide Transport Layer and Perovskite Active Layer for Flexible Perovskite Solar Cells: A Path Towards High-Throughput Manufacturing

Abstract

High-throughput roll-to-roll (R2R) manufacturing of perovskite solar cells (PSCs) is currently limited by thermal processes that take tens of minutes each, translating to impractically long annealing tools at high web speeds. In addition, PSCs are usually made with metal oxide transport layer materials that require high temperatures for thermal annealing. Here, we demonstrate the fabrication of PSCs using photonic curing, instead of thermal annealing, to convert NiOx directly from sol-gel precursors for hole transport layers and to crystallize methylammonium lead iodide (MAPbI3) active layers on flexible Willow® Glass substrates. Photonic curing uses short, intense pulses of light to process materials at a high speed, hence it is compatible with R2R manufacturing. We achieved power conversion efficiencies (PCEs) of 11.7% in forward-scan and 10.9% in reverse-scan for PSCs made with photonic cured NiOx and MAPbI3 films. Furthermore, both NiOx and MAPbI3 films could be processed with a single photonic curing pulse, with a web speed of 5.7 m/min, and still produce PCEs comparable to thermally annealed control samples. Based on the single-pulse photonic curing condition for each film, we project a web speed of 26 m/min, laying a pathway to high-throughput production of perovskite solar modules.

Elucidating Diiodomethane-Induced Improvement in Photonically Cured MAPbI3 Solar Cells

“…Perovskite precursor films absorb the radiant energy from the light pulses and convert them to the perovskite phase. It has been shown that this technique can complete the conversion to perovskite in a few milliseconds and is the fastest post-deposition process. − Furthermore, PC is versatile and can convert both the transport layer and the perovskite layer under different processing conditions. , Previously, we have reported using PC to achieve a champion power conversion efficiency (PCE) of 11.26% in a conversion time of 20 ms, which is lower than that of the thermally annealed devices. We note that all the processes with a conversion time of ≤ 2.5 s produce inferior device PCE compared to their thermally annealed counterparts. ,,, Thus, it is critical to understand the reasons behind the inferior PCE of PSCs made by ultrafast processes and explore mitigation strategies to make PSCs with high throughput without compromising performance.…”

Annealing Engineering in the Growth of Perovskite Grains

“…The intense pulsed light is a non-contact rapid heating method which can offer fast millisecond pulses of broad spectrum light (190-1100 nm) from xenon lamps [74]. Xenon lamps are used to provide high-energy pulse light to 150 J/cm 2 for perovskite annealing, and can achieve thin film crystallization at the millisecond scale [54,70,[75][76][77][78][79]. Druffel et al successfully employed intense pulsed light generated by a xenon lamp to sintering of MAPbI 3 on a mesoporous TiO 2 substrate for first time [76].…”

“…The diiodomethane (CH 2 I 2 ) additive can also improve surface coverage during rapid crystallization and enhance carrier transport [70]. The intense pulse annealing with halogen lamps was compatible with roll-to-roll manufacturing, which enabled production speeds of 26 m/min [77].…”

PbI2 Nanocrystal Growth by Atomic Layer Deposition from Pb(tmhd)2 and HI

“…ALD processes are self-limiting in principle, can be fine-tuned to result in ultrathin films of any required thickness, and are compatible with high throughput roll-to-roll (R2R) manufacturing. − ALD of lead halide perovskites will allow for greater control over the growth, morphology, and uniformity of the deposited thin films. Lead halide perovskites are most often deposited by spin coating, a type of solution processing that is restricted to small-area substrates and lacks reliability and conformality.…”