Inorganic Rubidium Cation as an Enhancer for Photovoltaic Performance and Moisture Stability of HC(NH₂)₂PbI₃ Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) based on organic monovalent cation (methylammonium or formamidinium) have shown excellent optoelectronic properties with high efficiencies above 22%, threatening the status of silicon solar cells. However, critical issues of long-term stability have to be solved for commercialization. The severe weakness of the state-of-the-art PSCs against moisture originates mainly from the hygroscopic organic cations. Here, rubidium (Rb) is suggested as a promising candidate for an inorganic-organic mixed cation system to enhance moisture-tolerance and photovoltaic performances of formamidinium lead iodide (FAPbI 3 ). Partial incorporation of Rb in FAPbI 3 tunes the tolerance factor and stabilizes the photoactive perovskite structure. Phase conversion from hexagonal yellow FAPbI 3 to trigonal black FAPbI 3 becomes favored when Rb is introduced. The authors find that the absorbance and fluorescence lifetime of 5% Rb-incorporated FAPbI 3 (Rb 0.05 FA 0.95 PbI 3 ) are enhanced than bare FAPbI 3 . Rb 0.05 FA 0.95 PbI 3 -based PSCs exhibit a best power conversion efficiency of 17.16%, which is much higher than that of the FAPbI 3 device (13.56%). Moreover, it is demonstrated that the Rb 0.05 FA 0.95 PbI 3 film shows superior stability against high humidity (85%) and the full device made with the mixed perovskite exhibits remarkable long-term stability under ambient condition without encapsulation, retaining the high performance for 1000 h. Figure 6. Fluorescence lifetime imaging microscopy (FLIM) images of a) FAPbI 3 and b) Rb 0.05 FA 0.95 PbI 3 films deposited on glass. c) Time-resolved photoluminescence (TRPL) spectra of FAPbI 3 and Rb 0.05 FA 0.95 PbI 3 films. Scale bar: 2 µm.

Phase Segregation in Cs-, Rb- and K-Doped Mixed-Cation (MA)x(FA)1–xPbI3 Hybrid Perovskites from Solid-State NMR

“…This finding challenges previous reports on rubidium incorporation into the perovskite lattice which were based on shifts observed in pXRD diffractograms and PL spectra. 14,17,18 A very recent work by Hu et al explains these shifts using EDX in terms of rubidium-induced bromide extraction, which is in excellent agreement with our findings described in the next paragraph. 44 Similarly to the Cs-doped HOPs, Rb-doped materials also exhibit improved long-term stability under high humidity conditions and light irradiation.…”

“…44 Similarly to the Cs-doped HOPs, Rb-doped materials also exhibit improved long-term stability under high humidity conditions and light irradiation. 14,17,18 We suggest that this can be explained by passivation of the perovskite phase by a fully inorganic RbPbI 3 layer, less prone to decomposition.…”

Room‐Temperature Vapor Deposition of Cobalt Nitride Nanofilms for Mesoscopic and Perovskite Solar Cells

“…[9] Meanwhile, perovskite solar cells (PSCs) exhibited unprecedented growth in power conversion efficiency, with a record certified efficiency of 22.1% in standard AM 1.5G condition. [16][17][18][19][20][21][22][23][24][25][26] However, the organic/inorganic hybrid solar cells are yet to meet the sufficient level required for their practical applications, particularly in terms of economic feasibility and long-term stability. [16][17][18][19][20][21][22][23][24][25][26] However, the organic/inorganic hybrid solar cells are yet to meet the sufficient level required for their practical applications, particularly in terms of economic feasibility and long-term stability.…”

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

“…Recently, the Rb + cation, which has an even smaller ionic radius (0.152 nm) than Cs + (0.181 nm), has also received wide attention because it can further enhance both the efficiency and stability of Rb-mixed perovskite solar cells. Park et al studied the (FA/Rb)PbI 3 system using the same Rb quantity ( ≤ 0.05) and, respectively, achieved PCEs of 16.15% and 16.2% [74,75]. More importantly, the significantly enhanced stability against moisture at 85% RH of Rb-mixed perovskites was highlighted.…”