Dopant‐Free, Amorphous–Crystalline Heterophase SnO₂Electron Transport Bilayer Enables >20% Efficiency in Triple‐Cation Perovskite Solar Cells

Abstract

Improving the ohmic contact and interfacial morphology between an electron transport layer (ETL) and perovskite film is the key to boost the efficiency of planar perovskite solar cells (PSCs). In the current work, an amorphous–crystalline heterophase tin oxide bilayer (Bi‐SnO2) ETL is prepared via a low‐temperature solution process. Compared with the amorphous SnO2 sol–gel film (SG‐SnO2) or the crystalline SnO2 nanoparticle (NP‐SnO2) counterparts, the heterophase Bi‐SnO2 ETL exhibits improved surface morphology, considerably fewer oxygen defects, and better energy band alignment with the perovskite without sacrificing the optical transmittance. The best PSC device (active area ≈ 0.09 cm2) based on a Bi‐SnO2 ETL is hysteresis‐less and achieves an outstanding power conversion efficiency of ≈20.39%, which is one of the highest efficiencies reported for SnO2‐triple cation perovskite system based on green antisolvent. More fascinatingly, large‐area PSCs (active areas of ≈3.55 cm2) based on the Bi‐SnO2 ETL also achieves an extraordinarily high efficiency of ≈14.93% with negligible hysteresis. The improved device performance of the Bi‐SnO2‐based PSC arises predominantly from the improved ohmic contact and suppressed bimolecular recombination at the ETL/perovskite interface. The tailored morphology and energy band structure of the Bi‐SnO2 has enabled the scalable fabrication of highly efficient, hysteresis‐less PSCs.

Colloidal SnO2‐Assisted CdS Electron Transport Layer Enables Efficient Electron Extraction for Planar Perovskite Solar Cells

“…[7][8][9] As one of extensively used architectures, the typical planar-type PSC comprises transparent conductive substrate, compact electron transport layer (ETL), perovskite absorber layer, hole transport layer (HTL), and metal electrode. [10][11][12] Thereinto, ETL plays a critical role in extracting and transport electrons from perovskite materials to conducting substrate. Hence, it is crucial to design high-quality ETLs with outstanding electron extraction capability for high-performance PSCs.…”

Dimensionality and Defect Engineering Using Fluoroaromatic Cations for Efficiency and Stability Enhancement in 3D/2D Perovskite Photovoltaics

“…Similarly, the detection of CC (≈284.8 eV) and CN bonds (≈286.5 eV) in the C 1s spectrum (Figure 3d) signified the presence of FA + /MA + ions in both perovskite films. [ 32,33 ] A CO bond (≈288.1 eV) is likely to emerge from the oxidized carbon species produced by the decomposition of the perovskite film upon interaction with ambient air during measurement. [ 34 ] Furthermore, Fourier transform infrared spectroscopy (FTIR) measurements were conducted in attenuated total reflection mode in a range of 4000–400 cm −1 to identify changes in the perovskite films.…”

Trifluoromethyl‐Group Bearing, Hydrophobic Bulky Cations as Defect Passivators for Highly Efficient, Stable Perovskite Solar Cells

“…Green antisolvent was prepared by mixing ethyl acetate (EA) and hexane (Hex) in 7:3 v v À1 similar to our previous works. [34,47,48] Fifty microliters of perovskite precursor solution was spin coated onto the ITO/SnO 2 substrate via two-step spin coating, i.e., 1500 rpm for 10 s followed by 5000 rpm for 30 s. At the 10 s interval during the second-step spin coating, 100 μL of the EA-Hex mixed antisolvent was rapidly dripped onto the spinning substrate. The perovskite films were then annealed at 150 C for 20 min in air.…”