Reconditioning perovskite films in vapor environments through repeated cation doping

Abstract

Perovskites have attracted considerable attention for application as high-efficiency photovoltaic devices owing to their low-cost and low-temperature fabrication. A good surface and high crystallinity are necessary for high-performance devices. We examine the negative effects of chemical ambiences on the perovskite crystal formation and morphology. The repeated cation doping (RCD) technique was developed to remedy these issues by gradually dropping methylammonium ions on top of about-to-form perovskite surfaces to cause recrystallization. RCD promotes pinhole-free, compact, and polygonal-like surfaces under various vapor conditions. Furthermore, it enhances the electronic properties and crystallization. The benefits of RCD extend beyond perovskites under vapor ambiences, as it can improve regular and wasted perovskites.

Enhancing High Humidity Stability of Quasi‐2D Perovskite Thin Films through Mixed Cation Doping and Solvent Engineering

“…Both fresh and aged MCD samples have larger crystal sizes with smaller variation compared to other types of samples. MCD sample showed significant improvement with regard to uniformity, grain size, and surface coverage, which could be explained by gradual recrystallization due to repeated cation deposition as explained in our previous work …”

“…Low E t values in MCD sample corresponds less electronic defects at the surface like dangling bonds or dislocation . We attribute this improvement to better surface passivation and more complete crystallization at the surface due the nature of repeated cation treatment . The significance of deep defect states can be further discussed by the ratio of the PV amplitudes measured at 1.1 and 1.7 eV (R 1.1eV /R 1.7eV ) as shown in Figure A (b).…”

“…The film was then annealed at 100 °C for 15 min under air (70% RH). The solution processing was further developed from repeated cation doping (RCD) as described in our published work . All spinning processes were conducted under nitrogen chamber with 10% RH.…”

“…The phase composition of the lead perovskite layers was investigated by X‐ray diffraction (XRD, Bruker D8 Discover). The electronic properties, defect formation, and degradation were identified by Modulated Surface Photovoltage (SPV) as described in our previous work . SPV spectra were measured in the fixed capacitor arrangement in air at a modulation frequency of 15 Hz.…”

Modifying morphology and defects of low-dimensional, semi-transparent perovskite thin films via solvent type

“…Compact TiO 2 layer was then deposited by spin-coating as described in our previous publications. 13,24 Lead halide mixtures of (PEA) 2 (MA) nÀ1 Pb n I n+1 Br 2n (n ¼ 1, 3, and 5) were prepared and studied in various solvent types and ratios. The perovskite precursors that were prepared according to Table 1 were separately dissolved in DMF, DMSO, GBL : DMSO ¼ 7 : 3, and DMF : DMSO ¼ 8 : 2.…”