Rear-Surface Passivation by Melaminium Iodide Additive for Stable and Hysteresis-less Perovskite Solar Cells

Abstract

Surface passivation of perovskite grains is one of the promising methods to reduce recombination and improve stability of perovskite solar cells (PSCs). We herein report the effect of a melaminium iodide additive on the photovoltaic performance of PSCs based on (FAPbI)(CsPbBr) perovskite. Cyclic -C═N- and primary amine in melamine are a good hydrogen bond acceptor and Lewis base, which can interact with both the organic cation and Lewis acidic lead iodide in the perovskite film. Melaminium iodide is synthesized and added to the precursor solution, which is directly spin-coated to form the perovskite film. The presence of melaminium iodide additive reduces the trap density from 1.02 × 10 to 0.645 × 10 cm, which leads to the reduction of nonradiative recombination and thereby improving the mean open-circuit voltage and the fill factor from 1.054 to 1.095 V and from 0.693 to 0.725 V, receptively. In addition, photocurrent-voltage hysteresis is reduced by the melaminium iodide additive, which results in an enhanced average power conversion efficiency, obtained from reverse and forward scanned data, from 15.86 to 17.32%. Time-resolved photoluminescence confirms that melaminium iodide plays a more important role in passivating the rear surface of the perovskite layer contacting the hole transporting spiro-MeOTAD layer. An aging test under a relative humidity of 65% reveals that melaminium iodide improves stability because of the suppression of the defect evolved by moisture.

Melamine Hydroiodide Functionalized MAPbI3 Perovskite with Enhanced Photovoltaic Performance and Stability in Ambient Atmosphere

“…There are many reports analyzing the origin of hysteresis in PSCs such as charge trapping and de‐trapping as a result of crystal defects, band bending between the different interfaces and ionic motions within perovskite. Park et al have reported adding melamine hydroiodide can effectively decrease the hysteresis of perovskite devices as surface passivation of perovskite grains . In our opinion, MALA has three amine groups that may provide hydrogen bonding to [PbI 6 ] 4− .…”

“…Park et al have reported adding melamine hydroiodide can effectively decrease the hysteresis of perovskite devices as surface passivation of perovskite grains. [20] In our opinion, MALA has three amine groups that may provide hydrogen bonding to [PbI 6 ] 4À . As shown in Scheme 1 and Figure S1b, Supporting Information, we suppose that some MALA through bonding to [PbI 6 ] 4À to affect the crystal lattice of the MAPbI 3 perovskite and others functioned as MAPbI 3 grains surface passivation.…”

Efficient Perovskite Solar Cells by Reducing Interface‐Mediated Recombination: a Bulky Amine Approach

“…Absorbance spectra and Tauc‐plots in Figure S8, Supporting Information, display little change in the absorption edges before and after NMAI treatment, which is consistent with results from XRD measurement. [ 45 ] Given the fact that typical 2D/3D stacked perovskite film configuration usually induces absorbance edge change, [ 21,23,46 ] we can infer that the quantity of formed low‐dimensional perovskite after NMAI treatment is indeed so negligible that it cannot affect the bandgap.…”

Recent Progresses on Defect Passivation toward Efficient Perovskite Solar Cells

“…This process deprotonated the imidazolium cations and released the imidazole, where cation exchange improved film quality. Kim et al reported a hysteresis‐free PSC with melaminium iodide additive, and the hysteresis index decreased from 0.1282 to 0.0674 (Figure g) …”