Humidity-Assisted Chlorination with Solid Protection Strategy for Efficient Air-Fabricated Inverted CsPbI₃ Perovskite Solar Cells

Abstract

Humidity-assisted chlorination with solid protection via 1,2-bis­(chlorodimethylsilyl)­ethane (Si–Cl) incorporation is demonstrated as an effective strategy to address water erosion for efficient air-fabricated inverted CsPbI3 perovskite solar cells (PSCs). Si–Cl molecules can rapidly react with water to reduce moisture erosion during deposition in air. In addition, the hydrolysis production of hydrogen chloride (HCl) can chlorinate CsPbI3 while the spontaneous polymerization of 1,2-bis­(hydroxydimethylsilyl)­ethane (Si–OH) builds a solid protection, which would improve the crystallization and phase stability of CsPbI3. Therefore, a champion efficiency of 18.93% with high open-circuit voltage of 1.176 V is achieved, which is the highest efficiency among the inverted inorganic PSCs. Furthermore, the moisture tolerance of both the CsPbI3 films and air-fabricated PSCs gets significant improvement. In addition, the nonencapsulated device shows good operational stability without efficiency drop after 1 sun illumination at 65 °C for 900 h.

In Situ Stabilized CsPbI3 for Air‐Fabricated Inverted Inorganic Perovskite Photovoltaics with Wide Humidity Operating Window

“…It has been proved that the carboxylate ions with the ionic and coordination bonds to CsPbI 3 can strongly anchor [PbI 6 ] 4– from phase transition. [ 21,33 ]…”

“…The two carboxylic groups on MAAC molecules can strongly interact with CsPbI 3 and improve the crystallization, trap passivation, and phase stability. [19,21] We conduct the hydrolyzed MAAD and MAAD doped CsPbI 3 films deposited in air (Figure S2, Supporting Information). In comparison with the hydrolysis MAAD, the peak of ν C = O is shifted to 1697 cm -1 from the initial 1710 cm -1 , and the difference (Δν COO ) between ν as and ν s of carboxyl groups is decreased from 135 to 72 cm −1 after incorporating into CsPbI 3 films.…”

“…It has been proved that the carboxylate ions with the ionic and coordination bonds to CsPbI 3 can strongly anchor [PbI 6 ] 4from phase transition. [21,33] In addition, the theoretical simulations from density functional theory (DFT) calculations (Figure S4, Supporting Information) point out that MAAC molecules feature a larger adsorption energy (ΔE ad ) of −0.72 eV on the CsPbI 3 surface than water molecules (−0.55 eV). The salinized carboxyl groups would gift more secure adsorption strength on the surface with ionic bonds, which would build solid shield to insulate moisture erosions during the air process.…”

“…In comparison, the inverted (p–i–n) structure can not only avoid the use of undesirable transport layers, but also features a compatible process with the tandem structure. [ 17–21 ] Unfortunately, the inverted CsPbI 3 PSCs are rarely reported and their highest efficiency is only 16.67%, which is far‐lagged from the regular. Furthermore, all the inverted CsPbI 3 PSCs are fabricated in a glovebox and their air fabrication is still a challenge.…”

“…Additionally, the water erosions would leave massive iodine vacancy (V I ) in CsPbI 3 films due to the large solvation enthalpy of halogen anions in water. [ 21,23 ] The V I traps would accelerate the phase transition by reducing the balance ionic bonds and act as the non‐radiative recombination to capture carriers. Furthermore, the crystallization of air‐deposited CsPbI 3 films would be further deteriorated under the rampant erosion of water molecules.…”