High-Performance Rigid and Flexible Perovskite Solar Cells with Low-Temperature Solution-Processable Binary Metal Oxide Hole-Transporting Materials

Abstract

To achieve high performance in perovskite solar cells (PSC), the holetransporting layer (HTL) is very important. In this work, we introduce a novel copper-chromium binary metal oxide as the hole-transporting material for PSC application. This low temperature solution-process HTL enables high performance PSC. The energy levels and phase compositions of the binary metal oxide can be modulated with different copper acetylacetonate (y)/ chromium acetylacetonate (z) volume ratios in the reacting solution precursors. X-ray diffraction and X-ray photoelectron spectroscopy show that both mono Cu y O(z ¼ 0) or Cr z O(y ¼ 0) and binary CuCrO 2 and CuCr 2 O 4 phases can be formed. The Cr-terminated polar CuCrO 2 component leads to films with superior wettability and compatibility with perovskite precursor solution, while the formation of high coverage uniform perovskite films is favorable for device fabrication. Unlike copper oxides, the copper-chromium binary metal oxide films have wide band gaps of around 3.1 eV, as well as suitable energy levels for both electron-blocking and hole-transporting. As a result, PSCs with this low-temperature solution processed copper-chromium binary metal oxide HTL have achieved high PCE of 17.19% on glass and 15.53% on flexible PET substrates, which is a significant enhancement over mono-metal oxide based devices.

Dopant‐Free Hole Transporting Materials for Perovskite Solar Cells

“…Two water‐soluble two dimensional transition metal dichalcogenide, MoS 2 and WS 2 are used as HTM in PSCs in a study by Huang et al The highest PCEs of 14.35 and 15.00% were obtained for the PSCs with MoS 2 and WS 2 , respectively. In a very recent study, Qin et al have achieved high PCE of 17.19% on glass and 15.53% on flexible PET substrates, introducing and employing a novel copper‐chromium binary metal oxide as HTM for PSCs . The copper‐chromium binary metal oxide films have wide band gaps of around 3.1 eV, as well as suitable energy levels for both electron‐blocking and hole‐transporting.…”

“…X‐ray diffraction spectra of Cu y Cr z O 2 films on FTO substrate with copper acetylacetonate and chromium acetylacetonate as precursors, which were mixed at different volume ratios (that is y:z) of: 1:0, 4:1, 2:1, 1:1, 1:2, 1:4, and 0:1, respectively. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

Tetra‐Propyl‐Substituted Copper (II) Phthalocyanine as Dopant‐Free Hole Transporting Material for Planar Perovskite Solar Cells

“…The CH 3 NH 3 PbI 3 / CuPrPc samples showed a decay time of 1.460 ns, whereas the CH 3 NH 3 PbI 3 /Spiro‐OMeTAD (doped) samples showed a longer decay lifetime of 1.542 ns. This indicates that CuPrPc has slightly better hole extraction capabilities than Spiro‐OMeTAD …”

Highly Efficient and Stable Flexible Perovskite Solar Cells with Metal Oxides Nanoparticle Charge Extraction Layers

“…Inorganic metal oxides semiconductors can be an appropriate alternative for PEDOT:PSS to improve the device stability and efficiency . Promising results were achieved with solution processable metal oxide HTL such as NiO x , and CuCrO 2 . Low‐temperature solution processing of CuCrO 2 allows manufacturing devices on plastic substrates.…”

“…Low‐temperature solution processing of CuCrO 2 allows manufacturing devices on plastic substrates. NiO x , which owns good hole conductivity, chemical stability, and good band alignment with perovskite layers and is a promising HTL in inverted perovskite solar cells, has a crucial annealing temperature of 300−500 °C, which prevents its direct application in flexible solar cells . If ones want to transfer a fabrication process from a rigid substrate to a polymer/transparent conducting oxide (TCO) flexible substrate, the use of low temperature (<150 °C for polyethylene terephthalate (PET)) processed ETL and HTL is a strict requirement .…”