Self‐Crystallized Multifunctional 2D Perovskite for Efficient and Stable Perovskite Solar Cells

Abstract

Recently, perovskite solar cells (PSC) with high power-conversion efficiency (PCE) and long-term stability have been achieved by employing 2D perovskite layers on 3D perovskite light absorbers. However, in-depth studies on the material and the interface between the two perovskite layers are still required to understand the role of the 2D perovskite in PSCs. Self-crystallization of 2D perovskite is successfully induced by deposition of benzyl ammonium iodide (BnAI) on top of a 3D perovskite light absorber. The self-crystallized 2D perovskite can perform a multifunctional role in facilitating hole transfer, owing to its random crystalline orientation and passivating traps in the 3D perovskite. The use of the multifunctional 2D perovskite (M2P) leads to improvement in PCE and long-term stability of PSCs both with and without organic hole transporting material (HTM), 2,2′,7,7′-tetrakis-(N,N-di-pmethoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) compared to the devices without the M2P.light absorbers have suffered from high defect density at the surfaces and grain boundaries, which can lead to nonradiative recombination and decrease PCEs of PSC. [6,8] Also, the volatile organic cation in the 3D perovskite lattice such as methylammonium (MA + ) and formamidinium (FA + ) degrades the stability of the perovskite itself and lifetime of PSCs. [9,10] In this regard, 2D perovskites have recently received substantial attention as they contain less-volatile bulkier organic cations, which can trigger passivation effect and lead to better water resistance, resulting in higher PCE and extended long-term stability of PSCs. Therefore, the deposition of 2D perovskite on top of the 3D perovskite has presented significant enhancement both in PCEs and stability of PSCs because the 3D/2D perovskite can take advantage of features of 2D perovskite while it can maintain the excellent optoelectronic properties of 3D perovskites. [11][12][13][14][15][16][17][18][19] In this study, we present the incorporation of self-crystallized multifunctional 2D perovskite (M2P) on top of a 3D perovskite (Cs 0.08 FA 0.77 MA 0.12 PbI 2.62 Br 0.35 ) light absorber. The self-crystallized M2P can facilitate hole transfer due to its randomly oriented crystalline structure and reduce the trap density in underlying 3D perovskite through a trap passivation effect. Therefore, the introduction of the M2P layer between 3D perovskite light absorber and hole transport material (HTM) in a PSC led to improvement in the PCE from 19.75% to 20.79% and long-term stability under simulated continuous sunlight, compared to the device without the M2P layer. Furthermore, we demonstrated the use of M2P as a hole-transporting layer (HTL) in a PSC without using the organic HTM, 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD), which resulted in PCE of 15.17%, which was greatly higher than PCE of the device without M2P (6.22%). Results and DiscussionWe developed layer-by-layer deposited self-crystallized 2D perovskite grown on top of 3D per...

Applications of Self‐Assembled Monolayers for Perovskite Solar Cells Interface Engineering to Address Efficiency and Stability

“…[30] Generally, the PSCs are optimized by compositional engineering of the absorber materials, optimizing the morphology, crystallinity, and grain size of a multicrystaline layer. [23][24][25][31][32][33] Other strategies like the incorporation of additives, [23,34] solvent engineering, [34,35] intermediate phase optimization, [36] mixed 2D and 3D systems, [37] or interface engineering [21] are often utilized to boost the performance toward either higher efficiency or stability. However, the surface underneath the perovskite layer also plays a vital role, as it dictates the film morphology and coverage.…”

Perovskite Single Crystals: Synthesis, Optoelectronic Properties, and Application

“…[ 134 ] Moreover, utilizing the randomly oriented crystalline structure of 2D PVSKs to facilitate hole transfer between 3D PVSK light absorber and HTL, the PCE improved from 19.75% to 20.79%. [ 135 ] Nowadays, phase‐pure 2D layered PVSK solar cells achieve a power conversion efficiency of 16.25% and after keeping them in 65 ± 10% humidity for 4680 h, under operation at 85 °C for 558 h, or continuous light illumination for 1100 h, the cells show <10% degradation. [ 87 ] The extraordinary stability of 2D PVSK provides extensive applications in many fields.…”

2D Nanomaterials for Effective Energy Scavenging

“…3 f displays the current density–voltage ( J – V ) properties, where it is observed that there is no current density ( J sc ) in the device under dark conditions [ 68 ]. The application of multi-functional 2D perovskites (M2P) with the hole transporting material (HTM) along with 2,2′,7,7′-tetrakis-( N , N -di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) light absorber increases both the effectiveness and the stability since M2P triggers faster hole transport and provides a passivation effect due to its randomly oriented crystal structure [ 69 ]. It is clear from Fig.…”

“…In addition, in the stage of spiro-OMeTAD on the basis of M2P requirements under the reverse and forward scan of the device, the stability of the perovskite solar cell improves by maintaining a maximum power point tracking to 80%, compared to 64%, in the case of applying M2P which is shown in Fig. 3 i [ 69 ]. The highest efficiency from a perovskite solar cell to date is 25.2% [ 70 ].…”