Improving Electron Extraction Ability and Device Stability of Perovskite Solar Cells Using a Compatible PCBM/AZO Electron Transporting Bilayer

Abstract

Due to the low temperature fabrication process and reduced hysteresis effect, inverted p-i-n structured perovskite solar cells (PSCs) with the PEDOT:PSS as the hole transporting layer and PCBM as the electron transporting layer have attracted considerable attention. However, the energy barrier at the interface between the PCBM layer and the metal electrode, which is due to an energy level mismatch, limits the electron extraction ability. In this work, an inorganic aluminum-doped zinc oxide (AZO) interlayer is inserted between the PCBM layer and the metal electrode so that electrons can be collected efficiently by the electrode. It is shown that with the help of the PCBM/AZO bilayer, the power conversion efficiency of PSCs is significantly improved, with negligible hysteresis and improved device stability. The UPS measurement shows that the AZO interlayer can effectively decrease the energy offset between PCBM and the metal electrode. The steady state photoluminescence, time-resolved photoluminescence, transient photocurrent, and transient photovoltage measurements show that the PSCs with the AZO interlayer have a longer radiative carrier recombination lifetime and more efficient charge extraction efficiency. Moreover, the introduction of the AZO interlayer could protect the underlying perovskite, and thus, greatly improve device stability.

Influence of Chloride/Iodide Ratio in MAPbI3-xClx Perovskite Solar Devices: Case of Low Temperature Processable AZO Sub-Layer

“…PCE values here obtained are low but it is worth mentioning that AZO implementation in a NIP perovskite solar cell has rarely been characterized. Most studies involving AZO concern PIN structures, where AZO is the top layer [18,55]. Nevertheless, a few studies start describing photovoltaic devices with AZO as a bottom layer as well with performance levels up to 12% or 16% using respectively mono or multi-cation perovskites [22,23,56].…”

ZnO as a Functional Material, a Review

“…AZO has specific benefits over the commonly used transparent electrode of indium tin oxide (ITO), such as a composition made of abundant materials, controllable doping level and bandgap engineering possibilities that make it, in principle more flexible in device applications. AZO has been shown as efficient transparent electrodes in Si [152], perovskite [153] and polymer [154] solar cells, as well as organic [155] and inorganic [156] LEDs, and as an antireflection coating for photovoltaic cells [157], also when not doped with Al [158] (see Figure 9).…”

An inherent instability study using ab initio computational methods and experimental validation of Pb(SCN)2 based perovskites for solar cell applications

“…A mesoporous TiO 2 layer was synthesized by diluting the TiO 2 paste in ethanol. PCBM solution acting as ETM was prepared inside the glove box, under the nitrogen (N 2 ) environment, by mixing 10 mg PCBM in 1 ml chlorobenzene 21,22 .…”

“…The chlorobenzene solution and 24 mM of Li-TFSI solution were mixed to realize the complete Spiro-MeOTAD solution for HTL fabrication. PEDOT:PSS solution acting as HTM was also prepared inside the glove box under inert conditions by mixing isopropanol and PEDOT:PSS in 3:1 volume ratio and filtered using 0.22 µm Nylon filter 21,22 . Further details on materials, reagents and equipment used for the synthesis of ETMs, HTMs and perovskite chemistries are mentioned in Supplementary Sects.…”