All‐Vacuum‐Processing for Fabrication of Efficient, Large‐Scale, and Flexible Inverted Perovskite Solar Cells

Abstract

Vacuum deposition of transporting layers, especially the hole‐transporting layer (HTL), is still a big challenge for the fabrication of large‐area perovskite solar cells (PSCs). In this work, efficient and large‐area PSCs are fabricated by thermal evaporation of all the layers. Poly(bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine) (PTAA) is used as the HTL, and a compact layer of PTAA with low thickness (2–10 nm) is successfully deposited using thermal evaporation. The optical and ultraviolet photoelectron spectroscopy (UPS) measurements prove that the evaporated PTAA has a great match with the single A‐cation methylammonium triiodide perovskite film in terms of quenching effect and band alignment. After fabrication of the inverted architecture using all‐vacuum‐processing, PSCs with power conversion of efficiencies (PCEs) of 19.4% for small area (0.054 cm2) and 18.1% for large area (1 cm2) are achieved, which are higher than those of solution‐based devices. A flexible PSC with PCE of 17.27% is also fabricated using this approach. Moreover, the fabricated PSCs, using the vacuum technique, show negligible hysteresis and good stability, better than the devices fabricated on spin‐coated PTAA. This work highlights the potential of vacuum deposition for scale‐up and commercialization of PSCs.

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

“…These devices are among the best reported all-evaporated perovskite solar cells without a solvent-based step in any of the utilized functional layers, achieving state-of-the-art PCEs above 19%. [23,24,39,41,116] It is worth noting that with only one undoped ultra-thin charge transport layer on the substrate side, the complexity of the employed layer stack sequence is significantly reduced compared to previously discussed all-evaporated layer stacks relaying on multi-layer charge transport materials. [34,114,117] The champion device prepared in this configuration achieves a PCE of 19.5%, an V oc of 1.08 V, a FF of 83.0%, and a J sc of 21.6 mA cm −2 in backward scan direction and a PCE of 19.3%, an V oc of 1.08 V, a FF of 81.7%, and a J sc of 21.9 mA cm −2 in forward scan direction, highlighting the low hysteresis observed in these devices.…”

“…[34] Moreover, this work pioneered the concept of fully vacuum-processed perovskite solar cells, which were further refined by employing organic and/or inorganic charge transport layers. [35][36][37][38][39][40][41] Recent co-evaporation studies have advanced beyond the simple single-cation CH 3 NH 3 PbI 3 material to triple-cation, [42] methylammonium-free, [43][44][45][46] as well as lead-free and leadreduced perovskite materials. [47][48][49] For solution-based perovskite solar cells, multi-cation and methylammonium-free perovskite materials have been reported to be a promising material system since they allow for easy bandgap tuning in addition to substantially better long-term stability.…”

Co‐Evaporated MAPbI3 with Graded Fermi Levels Enables Highly Performing, Scalable, and Flexible p‐i‐n Perovskite Solar Cells

“…[39] To date, there have been few reports of highly efficient, vapordeposited p-i-n PSCs as summarized in Table S1, Supporting Information, and just two with PCEs achieving 20%. [40,41] Moreover, to the best of our knowledge, the record PCE of a large area (1 cm 2 ) co-evaporated PSC are 18.1% [42] and 19% [9] for the p-i-n and n-i-p architecture respectively. The state of the art for the large area thermally evaporated PSCs together with their main characteristics are summarized in Table 1.…”

Efficient Thermally Evaporated γ‐CsPbI3 Perovskite Solar Cells

“…[ 25 ] While this is a noteworthy achievement, the high annealing temperature of 350 °C does not only increase the energy cost of fabricating such devices, but also limits their potential application on, for example, flexible substrates. [ 26 ]…”