Band Alignment Engineering between Planar SnO₂ and Halide Perovskites via Two-Step Annealing

Abstract

Managing defects in SnO2 is critical for improving the power conversion efficiency (PCE) of halide perovskite-based solar cells. However, typically reported SnO2‑based perovskite solar cells have inherent defects in the SnO2 layer, which lead to a lower PCE and hysteresis. Here, we report that a dual-coating approach for SnO2 with different annealing temperatures can simultaneously form a SnO2 layer with high crystallinity and uniform surface coverage. Along with these enhanced physical properties, the dual-coated SnO2 layer shows favorable band alignment with a mixed halide perovskite. After careful optimization of the dual-coating method, the average PCE of the perovskite solar cell based on the dual-coated SnO2 layer increases from 18.07 to 19.23% with a best-performing cell of 20.03%. Note that a facile two-step coating and annealing method can open new avenues to develop SnO2-based perovskite solar cells with stabilized and improved photovoltaic performances.

Cobalt Chloride Hexahydrate Assisted in Reducing Energy Loss in Perovskite Solar Cells with Record Open-Circuit Voltage of 1.20 V

“…25 Yip et al presented a dramatic enhancement of V OC in PSCs with the introduction of the SnO 2 /ZnO bilayer; 26 the favorable energy level improved the charge extraction and suppressed the interfacial recombination. Lee et al demonstrated a dual-coating method to deposit SnO 2 film at different annealing temperatures, 27 which leads to better energy level alignment with the perovskite layer and thus resulted in improved PSCs performance.…”

“…As per the previous report, hydroxyl groups exist on the surface of SnO 2 and can bind to metal sites. 27 There are two main active sites on the surface of the SnO 2 crystal, which could interact with water to form a hydroxyl group, a more hydroxylated surface when treated with UV-ozone. The defect sites (hydroxyl group) would lead to a trap state and cause nonradiative recombination.…”

Doping in Semiconductor Oxides‐Based Electron Transport Materials for Perovskite Solar Cells Application

“…Compared with ZnO and TiO 2 , SnO 2 is an n‐type semiconductor material with a wide bandgap, high transmittance, strong electron mobility, and high chemical stability. [ 97–100 ] Recently, the development of PSCs based on SnO 2 as an ETL has been very rapid, especially under the guidance of You's research group, which achieved commercial high‐quality SnO 2 film. [ 101,102 ] SnO 2 has a wider bandgap, which not only absorbs less UV light but also owns excellent chemical stability.…”

Advances in design engineering and merits of electron transporting layers in perovskite solar cells

“…However, most of the devices based on low-temperature solution-processed SnO 2 were reported to suffer from serious photocurrent hysteresis which makes it difficult to determine their real PCEs. 103,104 The optoelectronic properties of n-type semiconducting ZnO, such as a suitable conduction band energy level (BÀ4.17 eV for the CBM), large optical bandgap of 3.3 eV, high electronic mobility and high transmittance, are promising for applications in PSCs. [105][106][107] In addition, the low-temperature processed ZnO nanocrystalline thin films are favourable for flexible devices.…”