Efficient and Stable Tin‐Lead Mixed Perovskite Solar Cells Using Post‐Treatment Additive with Synergistic Effects

Abstract

Inhibiting the oxidation of Sn2+ during the crystallization process of Sn‐Pb mixed perovskite is found to be as important as the oxidation resistance of precursor solution to achieve high efficiency, but less investigated. Considering the excellent reduction feature of hydroquinone and the hydrophobicity of tert‐butyl group, an antioxidant 2,5‐di‐tert‐butylhydroquinone (DBHQ) was introduced into Sn‐Pb mixed perovskite films using an anti‐solvent approach. Interestingly, we find that DBHQ can act as function alterable additive during its utilization. On the one hand, DBHQ can restrict the oxidation of Sn2+ during the crystallization process, facilitating the fabrication of high‐quality perovskite film; on the other hand, the generated oxidation product 2,5‐di‐tert‐butyl‐1,4‐benzoquinone (DBBQ) can functionalize as defect passivator to inhibit the charge recombination. As a result, this synergetic effect renders the Sn‐Pb mixed PSC a power conversion efficiency (PCE) up to 23.0%, which is significantly higher than the reference device (19.6%). Furthermore, the unencapsulated DBQH‐modified PSCs exhibited excellent long‐term stability and thermal stability, with the devices maintaining 84.2% and 78.9% of the initial PCEs after aging at 25°C and 60°C for 800 h and 120 h under N2 atmosphere, respectively. Therefore, the functional alterable strategy provides a novel cornerstone for high‐performance Sn‐Pb mixed PSCs.

Dibenzo[b,d]thiophene Core Unit-Based Asymmetric Hole Transport Materials for Inverted Tin–Lead Perovskite Solar Cells

“…During the past 15 years, metal halide perovskite materials attracted wide attention due to their excellent photoelectric properties, such as tunable band gap, long charge carrier diffusion length, high absorption coefficient, and easy solution processability. − Up to now, the power conversion efficiency (PCE) of an organic–inorganic hybrid lead halide perovskite-based device has reached 26.1%, which is almost comparable to that of a monocrystalline silicon counterpart, making perovskite solar cell (PSC) a promising new generation photovoltaic technology. − Among the perovskite material family, Sn–Pb mixed perovskite material is widely investigated due to less Pb content and its potential application in tandem solar cells. − Although the single-junction Pb–Sn cells can achieve a band gap closer to the ideal Shockley–Queisser limit (∼1.25 eV), the ever-achieved PCE is still lower than 24%, and even much lower than that of pure Pb-based devices. − In addition, the appearance of additives and dopants in the hole transport layer (HTL) of normal (n–i–p) structured PSC would cause inferior PCE and rapid degradation of Sn–Pb mixed PSCs. , Therefore, the highly efficient Sn–Pb mixed PSCs are constrained in an inverted (p–i–n) device structure, in which PEDOT:PSS is most commonly employed as hole transport material (HTM) due to its merits of excellent wettability to perovskite precursors, high transmittance, and environmentally friendly solution preparation. − However, the acidity, hygroscopicity, and batch-to-batch variation in electrical and physical properties of PEDOT:PSS limit its future scope application . For this reason, it is highly desirable to develop materials to replace PEDOT:PSS in inverted Pb–Sn mixed PSCs. − Different form lead halide perovskite materials, Sn–Pb mixed perovskite usually possesses a more positive valence band (VB), located around −5.2–5.3 eV.…”