A Purified, Solvent‐Intercalated Precursor Complex for Wide‐Process‐Window Fabrication of Efficient Perovskite Solar Cells and Modules

Abstract

Ah igh-purity methylammonium lead iodide complex with intercalated dimethylformamide (DMF) molecules, CH 3 NH 3 PbI 3 ·DMF,i si ntroduced as an effective precursor material for fabricating high-quality solution-processed perovskite layers.S pin-coated films of the solvent-intercalated complex dissolved in pure dimethyl sulfoxide (DMSO) yielded thick, dense perovskite layers after thermal annealing.The low volatility of the pure DMSO solvent extended the allowable time for low-speed spin programs and considerably relaxed the precision needed for the antisolvent addition step.A no ptimized, reliable fabrication method was devised to take advantage of this extended process windowa nd resulted in highly consistent performance of perovskite solar cell devices, with up to 19.8 %p ower-conversion efficiency (PCE). The optimizedmethod was also used to fabricate a22.0 cm 2 ,eightcell module with 14.2 %P CE (active area) and 8.64 Voutput (1.08 V/cell).Hybrid organic-inorganic lead halide perovskites are promising materials for cost-effective printable photovoltaics. As ar esult of the enhanced purity of the reagents [1,2] and careful optimization of the perovskite layer fabrication process, conversion efficiencies have increased significantly since the first report on perovskite solar cells in 2009. [26] Thehighest certified power-conversion efficiency(PCE) now exceeds 23 %. [27,28] Forl arge-area devices,h owever, the certified PCE of as ubmodule still remains under 12 %. [28]

Engineering Halide Perovskite Crystals through Precursor Chemistry

“…According to classical nucleation theory, perovskite crystallization from a precursor solution is only expected to occur upon reaching supersaturation. As mentioned in Section , the most common solvents used to prepare perovskite precursor solution, including DMF and DMSO, have the high boiling point and low saturated vapor pressure (see Table ), making them difficult to rapidly evaporate from the wet precursor thin films during perovskite crystallization . As a result, residual solvent molecules undergo secondary bonding with solutes,9,13d,31,38 which degrades the crystal morphology and causes poor coverage of the thin films.…”

A Review on Additives for Halide Perovskite Solar Cells

“…Further research indicated that the intermediate phase was actually MA 2 Pb 3 I 8 (DMSO) 2 with nonstoichiometric ratio of MAI and PbI 2 . A more recently report by Ozaki et al showed that CH 3 NH 3 I was excluded from the complex when recrystallizing from CH 3 NH 3 I and PbI 2 in DMSO solution . Zuo et al developed a vapor induced intermediate phase (VIP) strategy to manipulate the morphology of perovskite films .…”

Toward Commercialization of Efficient and Stable Perovskite Solar Modules

“…Varying the concentration of high‐ D N additives in precursor solutions tunes the strength of lead‐solvent interactions, so as to fine‐control the crystallization and perovskite morphology (Figure 2b,c). [ 74–76 ] Due to the strong coordination of NMP and PbI 2 , Bu et al were able to inhibit the perovskite crystal growth by formation of PbI 2 •NMP adducts instead of perovskite‐DMF crystals in the perovskite precursor solution. The PbI 2 •NMP adducts have a much higher nucleation rate, allowing them to form a dense film, which then reacts in situ with embedded FAI/CsI to directly form α‐phase perovskite, bypassing the δ‐phase.…”