Significant performance enhancement of all‐inorganic CsPbBr₃ perovskite solar cells enabled by Nb‐doped SnO₂ as effective electron transport layer

Abstract

All‐inorganic CsPbBr3‐based perovskite solar cells (PSCs) have attracted great attention because of their high chemical and thermal stabilities in ambient air. However, the short‐circuit current density (Jsc) of CsPbBr3‐based PSCs is inadequate under solar illumination because of the wide bandgap, inefficient charge extraction and recombination loss, leading to lower power‐conversion efficiencies (PCEs). It is envisaged that in addition to narrowing the bandgap by alloying, Jsc of the PSCs could be enhanced by effective improvement of electron transportation, suppression of charge recombination at the interface between the perovskite and electron transporting layer (ETL), and tuning of the space charge field in the device. In this work, Nb‐doped SnO2 films as ETLs in the CsPbBr3‐based PSCs have been deposited at room temperature by high target utilization sputtering (HiTUS). Through optimizing the Nb doping level alone, the Jsc was increased by nearly 19%, from 7.51 to 8.92 mA·cm−2 and the PCE was enhanced by 27% from 6.73% to 8.54%. The overall benefit by replacing the spin‐coated SnO2 with sputtered SnO2 with Nb doping was up to 39% increase in Jsc and 62% increase in PCE. Moreover, the PCE of the optimized device showed negligible degradation over exposure to ambient environment (T ˜ 25 °C, RH˜45%), with 95.4% of the original PCE being maintained after storing the device for 1200 h.

Annealing-Free SnO2 Layers for Improved Fill Factor of Perovskite Solar Cells

“…Finally, the NPE-SnO 2 films were obtained under such a low moisture and oxygen atmosphere, which potentially facilitated higher-quality SnO 2 ETLs . And more importantly, the processing time of NPE-SnO 2 (only 1 min) is sharply shortened compared to that of the traditional annealing process (A-SnO 2 , about 30 min) . To confirm the film morphology quality, we conducted a scanning electron microscopy (SEM) analysis on NPE-SnO 2 and A-SnO 2 with the test structure of Glass/ITO/ETL.…”

“…15 And more importantly, the processing time of NPE-SnO 2 (only 1 min) is sharply shortened compared to that of the traditional annealing process (A-SnO 2 , about 30 min). 16 To confirm the film morphology quality, we conducted a scanning electron microscopy (SEM) analysis on NPE-SnO 2 and A-SnO 2 with the test structure of Glass/ITO/ETL. As shown in Figure 1a,b, the NPE-SnO 2 film without pinholes and cracks fully covers the conducting substrate, while there are aggregates and cracks on the surface of A-SnO 2 .…”

Recent Progress of Carbon‐Based Inorganic Perovskite Solar Cells: From Efficiency to Stability

“…Accordingly, various novel synthesis approaches have been explored, including atomic layer deposition (ALD), [57,355] chemical bath deposition, [48] spray-coating, [170] hydrothermal method, [47] and magnetron sputtering. [63,64,[356][357][358] Typically, Lee et al applied c-TiO 2 deposited by spray-coating process as ETL in C-IPSCs, achieving the PCEs of 12.91% and 10.08% for small-area devices (0.12 cm 2 ) and submodules (25 cm 2 ), respectively. [170] Another method to enhance the properties of ETLs is doping.…”

Doping Electron Transporting Layer: An Effective Method to Enhance JSC of All‐Inorganic Perovskite Solar Cells

“…[8] In this issue of Energy & Environmental Materials, Guo et al increased the J SC of PSCs around 19% (from 7.51 to 8.92 mA cm −2 ) by employing high target utilization sputtering Nb-doped SnO 2 ETLs. [9] The carrier concentration of ETLs can be increased from 10 18 to 10 19 cm −3 by 3%…”