Single-Crystal Methylammonium-Free Perovskite Solar Cells with Efficiencies Exceeding 24% and High Thermal Stability

Abstract

Grain-free single-crystal perovskites offer a potential avenue to the stability of advance perovskite solar cells (PSCs) beyond that of polycrystalline films. Recent progress in single-crystal PSCs (SC-PSCs) has come primarily from methylammonium (MA)-containing (e.g., FA 0.6 MA 0.4 PbI 3 ) perovskite devices, which have achieved a 23.1% power conversion efficiency (PCE). Yet, such perovskites are intrinsically vulnerable to thermal stresses, given the relative volatility of the MA molecule within the perovskite structure. Herein, we demonstrate MA-free SC-PSCs based on an ∼20-μm-thick Cs 0.05 FA 0.95 PbI 3 single-crystal absorber layer, which achieves new stability and efficiency benchmarks for SC-PSCs. Our devices exhibit 24.29% PCE and retain 90% of their initial efficiency after 900 h at 53 °C. Accelerated aging tests on the Cs 0.05 FA 0.95 PbI 3 single crystals show that they endured the damp heat test (85 °C/65% RH) approximately twice as long as polycrystalline films of the same composition. These results indicate that MA-free FAPbI 3 -based SCs are promising candidates to develop the stability and efficiency of PSCs on the road to commercialization.

Annual research review of perovskite solar cells in 2023

“…The devices achieved new stability (maintained 90% efficiency after 900 h at 53 • C) and high efficiency of 24.29% for single-crystal PSCs. Accelerated aging tests showed that they endured the damp heat test, and Cs 0.05 FA 0.95 PbI 3 single crystals approximately twice as long as polycrystalline films at 85 • C/65% RH [178]. Liu et al resolved the surface contamination issue by introducing an amphiphilic long-chain organic amine (cetyltrimethylammonium chloride, CTAC) into the PVK crystal growth solution.…”

Using Electron Microscopy to Explore Solar Cell Interfaces: Microstructures, Efficiency, and Stability

“…16,43,44 The current efficiency record for monocrystalline perovskite solar cells is 24.29%, which shows good stability but lower efficiency. 8 In atomic-scale imaging studies, as shown in Figure 2(b), most perovskite grain boundaries are sharp and strainfree, and amorphization is less commonly observed, which may be why perovskite grain boundaries often appear benign. 24 Because the atomic-scale characterization of perovskite materials is difficult, earlier studies were mainly theoretical, especially those related to perovskite grain boundaries.…”

“…Several studies based on conductive atomic force microscopy (c-AFM) and Kelvin probe force microscopy (KPFM) observed that a higher photovoltage and current were generated at the grain boundaries of MAPbI 3 under illumination, which promoted carrier extraction, showing that grain boundaries were beneficial to carrier transport. ,− Phung et al investigated the role of MAPbI 3 grain boundaries on the migration of ionic defects using SEM and PL microscopy and found that the luminescence time of polycrystalline was much longer than that of single crystals . Some literature indicates that band bending due to grain boundaries promotes carrier separation and collection, and compounding may only occur at defect locations rather than at the overall grain boundaries. ,, The current efficiency record for monocrystalline perovskite solar cells is 24.29%, which shows good stability but lower efficiency . In atomic-scale imaging studies, as shown in Figure (b), most perovskite grain boundaries are sharp and strain-free, and amorphization is less commonly observed, which may be why perovskite grain boundaries often appear benign …”

“…In contrast, for thin-film cells (such as perovskites, CdTe, and Cu(In,Ga)Se 2 (CIGS)), efficiency records all originate from polycrystalline devices. In some cases, their values even exceed those of single-crystal devices under similar contact. , This has also aroused a lot of curiosity among researchers about grain boundary properties. In addition to grain boundaries, other interfaces in devices (twin boundaries, stacking faults, and phase boundaries) also affect their performance to varying degrees, including efficiency loss, impurity enrichment, ion migration, etc.…”

Self-Heating of Planar Perovskite Solar Cells Depending on Active Material Properties

“…A higher temperature increases recombination and limits open-circuit voltage, which typically dominates the temperature coefficient of power production. , On the other hand, an elevated temperature − and temperature variations present challenges for the device stability of PSCs. Although the thermal stability of PSCs is under active development, − a higher operation temperature is likely to accelerate material degradation, even in devices that are regarded very stable, such as silicon solar cells . Thus, operation temperature matters, even if the critical issues of thermal stability , are solved.…”