Efficient Electron Transport Scaffold Made up of Submicron TiO₂ Spheres for High-Performance Hole-Transport Material Free Perovskite Solar Cells

Abstract

Nanoporous submicron TiO 2 spheres of diameters around 200 nm are synthesized by a hydrothermal process and used as a scaffold layer for improving light absorption, charge transportation, as well as photovoltaic performance in holetransport-layer free perovskite solar cells employing carbon counter electrodes. The TiO 2 submicron spheres show a porous feature with high specific surface area, which is essential for perovskite infiltration, charge extraction, and transportation in mesoscopic perovskite solar cells. Furthermore, big spheres exhibit better light scattering property compared to traditional TiO 2 nanoparticles, thus enhancing light absorption in corresponding devices. The present perovskite solar cells employ a TiO 2 scaffold layer of optimized thickness of about 600 nm and show an average power conversion efficiency of 13.46 ± 0.41%, which is 18.4% higher than that of counterparts based on TiO 2 nanoparticle (11.37 ± 0.40%). The champion cell exhibits an impressive efficiency of 14.3%, which is very competitive in perovskite solar cells without a hole transport layer using a carbon electrode. Moreover, our carbon based perovskite solar cell shows excellent long-term stability against moisture and heat with negligible degradation for 210 days of storage under ambient conditions. KEYWORDS: TiO 2 nanoporous sphere, HTM-free perovskite solar cells, TiO 2 scaffold layer, CH 3 NH 3 PbI 3 , carbon counter electrodes, long-term stability

Fully Air‐Processed Carbon‐Based Efficient Hole Conductor Free Planar Heterojunction Perovskite Solar Cells With High Reproducibility and Stability

“…Figure d is the X‐ray diffraction (XRD) spectra of FTO, FTO/TiO 2 , and FTO/TiO 2 /CH 3 NH 3 PbI 3 films. From XRD results, we can find the appearance of a small peak at around 25°, indicating the presence of TiO 2 , the same as reported . For perovskite layer, there is a small PbI 2 peak, and this will be beneficial for PVSCs since the presence of PbI 2 can help passivate grain boundaries and reduce charge traps inside the crystals …”

Surface Passivation of Perovskite Solar Cells Toward Improved Efficiency and Stability

“…The similar half-widths of all the perovskites suggest that organic combinations have little impact on the crystal size. Interestingly, we observed a significant decrease in the intensity of the diffraction peak for TTC/C 60 -coated perovskite, which might be a result of the improved coverage of the perovskite surface [ 32 ]. The UV–Vis spectra of these perovskite films (Fig.…”

Towards Simplifying the Device Structure of High‐Performance Perovskite Solar Cells

“…The most common one is based on a conventional regular structure (TCO/ETL/perovskite/gold or carbon) (Table 2). [25,48,86,87,[89][90][91][92][93][94][95][96][97][98][99][100][101][102][103] This type was first designed by Etgar and co-workers in 2012. The other type is the printable Figure 6.…”

“…The most common one is based on a conventional regular structure (TCO/ETL/perovskite/gold or carbon) ( Table 2 ). [ 25,48,86,87,89–103 ] This type was first designed by Etgar and co‐workers in 2012. The other type is the printable mesoscopic structure (TCO/ETL/ZrO 2 insulated layer/carbon: perovskite) ( Table 3 ).…”

“…As reported by Zhao et al, the HTL‐free PSC with a carbon electrode could remain stable in the ambient atmosphere for more than 200 days. [ 96 ] Ishikawa et al constructed HTL‐free PSC with a graphene electrode and confirmed its superior stability. [ 101 ]…”