Interfacial Strain Release from the WS₂/CsPbBr₃ van der Waals Heterostructure for 1.7 V Voltage All‐Inorganic Perovskite Solar Cells

Abstract

Perovskite lattice distortion induced by residual tensile strain from the thermal expansion mismatch between the electron-transporting layer (ETL) and perovskite film causes a sluggish charge extraction and transfer dynamics in all-inorganic CsPbBr 3 perovskite solar cells (PSCs) because of their higher crystallization temperatures and thermal expansion coefficients. Herein, the interfacial strain is released by fabricating a WS 2 /CsPbBr 3 van der Waals heterostructure owing to their matched crystal lattice structure and the atomically smooth dangling bond-free surface to act as a lubricant between ETL and CsPbBr 3 perovskite. Arising from the strain-released interface and condensed perovskite lattice, the best device achieves an efficiency of 10.65 % with an ultrahigh open-circuit voltage of 1.70 V and significantly improved stability under persistent light irradiation and humidity (80 %) attack over 120 days.

Managing Defects Density and Interfacial Strain via Underlayer Engineering for Inverted CsPbI2Br Perovskite Solar Cells with All‐Layer Dopant‐Free

“…In comparison, when TS-CuPc-i is applied (Figure 3b,c), the (100) peak is negligibly shifted in the same depth range, indicative of less-distorted perovskite lattice and hence evidently reduced tensile strain near the HTL/PVK interface. [34] To better understand such a difference, thermal expansion coefficient (α TE ) was estimated for CsPbI 2 Br perovskite and dopant-free Spiro-OMeTAD, respectively, using the previously reported method. [28,35] By plotting d-spacing with ambient temperature (Figure 3d and Figure S10, Supporting Information), the α TE of CsPbI 2 Br is revealed to be almost one order larger than that of Spiro-OMeTAD.…”

Stability of Perovskite Solar Cells: Degradation Mechanisms and Remedies

“…Better-aligned energy levels, suppressed grain boundary recombination losses, and cascade charge transfer yielded a device with PCE of ∼20.3% with excellent air, photo, and thermal stabilities (Tyagi et al, 2020). All-inorganic PSCs are highly stable and improving their efficiency can be a key to achieve commercial PSCs (Duan et al, 2019;Zhou et al, 2020;Du et al, 2021).…”

Interfaces and Interfacial Layers in Inorganic Perovskite Solar Cells

“…Thee lectronic band structure and the corresponding materials properties of inorganic perovskite layers such as the absorption coefficient and band gap can be significantly altered by element substitution at the Pb and/or Is ites.F or CsPbBr 3 ,the VB near the Fermi level is mainly determined by the Br 4p and Pb 6s orbitals,while the main contributions to the CB come from the Pb 6p and Br 4p states.Thus,tuning the composition of inorganic perovskites can greatly impact their energy level match with adjacent interlayers.When the halide composition is changed, the band gaps of CsPbX 3 can be tuned from 1.73 eV for CsPbI 3 to 2.30 eV for CsPbBr 3 ,where a V OC of 1.70 Vcan be achieved. [63] As for the lead site,aseries of CsPb 1Àx Sn x IBr 2 perovskite films present tunable band gaps from 2.04 eV to 1.64 eV. [64] TheV Bs hifts upwards from À5.79 eV for CsPbI 2 Br to À5.57 eV for CsPb 0.55 Sn 0.45 I 2 Br, which relaxes the requirements for al ow-lying VB of the HTL.…”