Novel PHA Organic Spacer Increases Interlayer Interactions for High Efficiency in 2D Ruddlesden–Popper CsPbI₃ Solar Cells

Abstract

The two-dimensional (2D) Ruddlesden–Popper (RP) CsPbI3 with hydrophobic organic spacers can significantly improve the environmental and phase stability of photovoltaic devices by suppressing ion migration and inducing steric hindrance. However, due to the multiple-quantum-well structure, these spacer cations lead to weak interactions in 2D RP CsPbI3, which seriously affect the carrier transport. Here, a novel N–H-group-rich phenylhydrazine spacer, namely, PHA, was developed for 2D RP CsPbI3 perovskite solar cells (PSCs). A series of characterizations confirm that the 2D perovskites using PHA spacers enhanced the N–H···I hydrogen-bonding interaction between the organic spacer cations and the [PbI6]4– inorganic layer and accelerated the crystallization rate of the perovskite film, which was beneficial to the preparation of high-quality films with preferred vertical orientation, large grain size, and dense morphology. Meanwhile, the trap state density of the as-prepared 2D RP perovskite films is significantly reduced to enable efficient charge carrier transport. As a result, the (PHA)2Cs4Pb5I16 PSCs achieved a performance of 16.23% with good environmental stability. This work provides a simple organic spacer selection scheme to realize interaction optimization in 2D RP CsPbI3 to develop efficient and stable PSCs.

Tuning charge carrier dynamics through spacer cation functionalization in layered halide perovskites: an ab initio quantum dynamics study

“…[38][39][40] In this regard, the targeted functionalization of spacer cations unlocks viable strategies for fine-tuning the structural stability and charge carrier dynamics of LHPs at room temperature. 21,30,41,42 Due to similar steric parameters, the substitution of fluorine (van der Waals radii B 147 ps) with hydrogen (radii B 110 pm) in spacer cations maintains the overall crystal structure of LHPs without much geometric distortion. 43 The high electronegativity of fluorine can substantially modify the organic-inorganic sublattice coupling through C-FÁ Á ÁX (X is halogen), FÁ Á Áp, and hydrogen bonding interactions.…”

Structural Tailoring the Phenylenediamine Isomers to Obtain 2D Dion–Jacobson Tin Perovskite Solar Cells with Record Efficiency

“…First, both SEM and AFM illustrate that the p ‐PDA‐Sn perovskite film has obvious holes and uneven morphology, which leads to its highest root‐mean‐square (RMS) roughness (45.35 nm) ( Figure a–c and Figure S7, Supporting Information). [ 41 ] Obviously, the RMS of m ‐PDA‐Sn and o ‐PDA‐Sn films decreased to 24.96 and 18.98 nm, respectively, which indicated that the morphology of the films was improved. In addition, compared with m ‐PDA‐Sn film, o ‐PDA‐Sn film is denser with fewer holes, which is beneficial to interface contact and improves carrier transport.…”

“…Compared with the other two devices, o ‐PDA‐Sn device has larger recombination resistance ( R rec ) and smaller transmission resistance ( R s ), indicating that the ortho ‐structure of PDA can inhibit charge recombination (Table S9, Supporting Information). [ 41 ] Then, the carrier transport lifetime ( τ trans ), carrier recombination lifetime ( τ rec ), and charge collection efficiency ( η cc ) of the device were probed by intensity‐modulated photovoltage and photocurrent spectra (IMVS and IMPS; Figure 4i and Figure S12, Supporting Information). These results show that compared with p ‐PDA‐Sn and m ‐PDA‐Sn devices, o ‐PDA‐Sn devices have larger τ rec and η cc and smaller τ trans , which further shows that the o‐ PDA is beneficial to the extraction and transmission of carriers and can reduce the recombination of carriers.…”

Synergy of 3D and 2D Perovskites for Durable, Efficient Solar Cells and Beyond

“…Similar to 3D halide perovskites, defect passivation and improvements in crystallinity can suppress defect-mediated degradation pathways in 2D halide perovskites and improve device stability. − Yukta et al demonstrated an improvement in unencapsulated device stability both at RT/60%RH and at 85 °C, as well as an increased water contact angle, for (NDA)(MA) 3 Pb 4 I 13 (NDA = 1,5-diamino­naphthalene, n = 4) treated with NH 4 SCN . The improvement in stability was attributed to a reduced defect concentration and increased crystallinity as a result of the addition of NH 4 SCN, which regulates crystal growth and suppresses defects through the synergistic occupation of A-sites by NH 4 + and X-sites by SCN – .…”

“…The reduction of defects and increased crystallinity improved the stability of 10%NMA devices in air compared to pure BA devices. Yao et al likewise improved film crystallinity and as a result device stability in Cs-based RP halide perovskites by replacing phenyl­ammonium (PA + ) with phenyl­hydrazinium (PHA + ) to strengthen the spacer cation–inorganic layer hydrogen bond . Li et al utilized 4-(2-aminoethyl)­pyridinium (4-AEP + ) to simultaneously act as the spacer cation and modulate crystallization kinetics by complexing with Pb 2+ , improving crystallinity and stability relative to the nonfunctionalized PEA + …”