Analysis of the UV–Ozone‐Treated SnO₂ Electron Transporting Layer in Planar Perovskite Solar Cells for High Performance and Reduced Hysteresis

Abstract

Tin oxide (SnO2) is widely used as an electron transporting layer (ETL) in perovskite solar cells (PSCs) because of its good transparency, band alignment to perovskite, and stability. The interface between the ETL and the perovskite in the PSCs affects the charge extraction process and influences the optoelectronic properties. Surface treatment of SnO2, such as the UV–ozone (UVO) treatment, is shown to enhance the efficiency and reduce the light soaking effect of the PSCs. Herein, the success in control and suppressing hysteresis reaching the highest photoconversion efficiency of 19.4% with negligible hysteresis for the growth of the devices on SnO2 treated with UVO for 60 min is reported. The wettability of the treated SnO2 is well matched with the polar solvent of the perovskite solution, leading to complete coverage of the substrate, although the treatment does not affect the morphology and the crystallinity of the perovskite thin films. Impedance spectroscopy measurement analysis clearly indicates the decrease in the recombination rate after the UVO treatment and the reduction in low frequency capacitance causing a reduction in the current–potential curve hysteresis.

Hysteresis-less and stable perovskite solar cells with a self-assembled monolayer

“…The J-V hysteresis seemed very small at this scan rate, and the hysteresis index (HI) defined in the "Methods" section was close to zero. This small hysteresis is consistent with literature, in which SnO 2 was used as the ETL in PSCs 25,26 . However, the hysteresis increased with decreasing the scan rates from 200 to 10 mV s −1 (Fig.…”

Preferred Growth Direction by PbS Nanoplatelets Preserves Perovskite Infrared Light Harvesting for Stable, Reproducible, and Efficient Solar Cells

“…In order to corroborate the strong and robust impact of the PbS NPLs on device stability, the same devices were fabricated also under ambient conditions (in air, 25 °C and 50–55% RH). While the environmental surroundings usually play a dramatic role in achieving reproducible device performances and properties, [ 65 ] the solar cell parameters of devices fabricated under ambient conditions, see Figure 7 and Figure S10, Supporting Information, show a similar trend as the ones fabricated under inert conditions, [ 66 ] and a record PCE of ≈17% is achieved with the addition of PbS NPLs with 0.5 mg mL −1 concentration. It is worth to note that under these conditions the PbS NPLs have also more evident benefits, as the PCE of the device based on 0.5 mg mL of PbS NPLs is 7% higher than the control device, see Figure 7a, and is more reproducible, see Figure 7b.…”

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

“…UV‐Ozone (UVO) treatment could not only remove organic residues on the surface of semiconductor oxide and then enhance the wettability, which is beneficial to the crystallinity of perovskite, but also reduce oxygen vacancy‐related defects, thus inhibiting the hysteresis of PSCs. For instance, Méndez et al [ 262 ] reported the efficient and negligible hysteresis PSCs by UVO treatment on SnO 2 ETL. Figure a–c shows the hysteresis effect of PSCs with different UVO treatment time.…”

“…Reproduced with permission. [ 262 ] Copyright 2019, WILEY‐VCH. e) J – V curves of PSCs based on different ETLs prepared at 50 °C.…”