Crosslinkable and Chelatable Organic Ligand Enables Interfaces and Grains Collaborative Passivation for Efficient and Stable Perovskite Solar Cells

Abstract

as a potential green energy-generating technology, proving to be a game-changer in photovoltaics. [1][2][3] Significant efforts, including material design, thin-film growth control, and interface engineering, have been devoted to promoting device performance. [4][5][6] Within only a few years, the power conversion efficiencies (PCEs) of single-junction PerSCs have been enhanced to 20% threshold. [7][8][9][10] Despite the leaps and bounds in efficiency, the stability of PerSCs, especially moisture/ water and thermal stability, is still a severe concern, since a long-term environmental atmosphere potentially makes degradation or phase transition of the perovskite. [11][12][13] Accordingly, device instability issues must be overcome along with the improvement of the PCE of PerSCs.Interface and grains control plays a vital role in achieving highly efficient and stable PerSCs. Nonradiative recombination caused by traps/defects existing at the interface and grain boundaries (GBs) impairs charge-density buildup and diminishes the photo-voltage of devices. [14][15][16] Moreover, these defects are the attack points of external factors such as water and thermal, resulting in the decomposition of perovskite. [17,18] Uncoordinated Pb 2+ ion is one typical ion defect on the surface and GBs of perovskite which seriously injures the device performance. [19] Previous studies have been carried out toward solving uncoordinated Pb 2+ ions in achieving high-efficiency PerSCs. [20] A series of organic molecules containing lone pair electrons on oxygen, sulfur, or nitrogen (such as pyridine, thiophene, benzoquinone, and crown ether) have been selected to reduce those defect sites by coordination bonds. [21][22][23] For instance, a series of crown ethers were employed to suppress uncoordinated surface defects, yielding an improved PCE exceeding 23% and achieving enhanced stability under ambient and operational conditions. [24] Moreover, as for the n-i-p structured PerSCs, SnO 2 has been regarded as a promising candidate for electron transport material. [25] However, surface traps/defects existing at the SnO 2 / perovskite interface are disadvantageous for charge transport. Therefore, optimizing the SnO 2 /perovskite interface to suppress the formation of surface traps/defects is vital to boosting device performance. [26,27] Generally, further modificationThe organic-inorganic halide perovskite solar cell (PerSC) is the state-of-theart emerging photovoltaic technology. However, the environmental water/ moisture and temperature-induced intrinsic degradation and phase transition of perovskite greatly retard the commercialization process. Herein, a dual-functional organic ligand, 4,7-bis((4-vinylbenzyl)oxy)-1,10-phenanthroline (namely, C1), with crosslinkable styrene side-chains and chelatable phenanthroline backbone, synthesized via a cost-effective Williamson reaction, is introduced for collaborative electrode interface and perovskite grain boundaries (GBs) engineering. C1 can chemically chelate with Sn 4+ in the SnO 2 electron transport...

Recent advances of crosslinkable organic semiconductors in achieving solution-processed and stable optoelectronic devices

“…Therefore, designing molecules comprising the function of crosslinking and coordination is an efficient method to effectively lower the traps/defects and enhance the long-term stability of PerSCs. 219,220 For instance, Tan et al synthesized a dual-functional organic ligand (C 1 ) with crosslinkable styrene side-chains and a chelatable phenanthroline backbone. 219 C 1 can chemically chelate with Sn 4+ in the SnO 2 electron transport layer and Pb 2+ in the perovskite layer via coordination bonds, suppressing nonradiative recombination caused by traps/defects existing at the interface and GBs (Fig.…”

“…219,220 For instance, Tan et al synthesized a dual-functional organic ligand (C 1 ) with crosslinkable styrene side-chains and a chelatable phenanthroline backbone. 219 C 1 can chemically chelate with Sn 4+ in the SnO 2 electron transport layer and Pb 2+ in the perovskite layer via coordination bonds, suppressing nonradiative recombination caused by traps/defects existing at the interface and GBs (Fig. 19a).…”

Thermal degradation of the bulk and interfacial traps at 85 °C in perovskite photovoltaics

“…Various strategies have been ardently reported to passivate the traps and defects of polycrystalline perovskite with great improvements in stability against air, light, and heat. 26–35 For example, Jeong et al . modified perovskite with pseudo-halide anion formate (HCOO − ) to control the anion vacancies at the grain boundaries and surfaces of the film.…”

“…Various strategies have been ardently reported to passivate the traps and defects of polycrystalline perovskite with great improvements in stability against air, light, and heat. [26][27][28][29][30][31][32][33][34][35] For example, Jeong et al modified perovskite with pseudo-halide anion formate (HCOO − ) to control the anion vacancies at the grain boundaries and surfaces of the film. 36 Li et al doped alkali fluorides into the perovskite and achieved 1000 h stability at 85 °C retaining over 80% of the initial efficiency with the spiro-OMeTAD-based hole-transport layer (HTL), confirming that the degradation of PSC depends more on perovskite defects than on the electrode materials.…”

Reconstructing the amorphous and defective surface for efficient and stable perovskite solar cells

“…They inevitably induce the nonradiative recombination and degradation at the heterointerfaces, harming the efficiency and stability [22]. Many materials, including organic molecules with functional groups [23][24][25][26], low dimen-sional (one dimensional (1D) and 2D) perovskites [27][28][29][30][31][32] and zwitterionic compounds [33][34][35], have been introduced to passivate the defective perovskite surfaces [36]. The strategies of removing the defective surface layers have been also proposed to stabilize PSCs.…”