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Abstract:

An open-cage bis[60]fulleroid (OC) was applied as electron transport material (ETM) in tin (Sn) halide perovskite solar cells (PSCs). Due to the reduced offset between the energy levels of Sn-based...

Abstract:

Perovskite solar cells (PSCs) comprise a solid perovskite absorber sandwiched between several layers of different charge-selective materials, ensuring unidirectional current flow and high voltage output of the devices. A ‘buffer material’ between the electron-selective layer and the metal electrode in p-type/intrinsic/n-type (p-i-n) PSCs (also known as inverted PSCs) enables electrons to flow from the electron-selective layer to the electrode. Furthermore, it acts as a barrier inhibiting the inter-diffusion of harmful species into or degradation products out of the perovskite absorber. Thus far, evaporable organic molecules and atomic-layer-deposited metal oxides have been successful, but each has specific imperfections. Here we report a chemically stable and multifunctional buffer material, ytterbium oxide (YbOx), for p-i-n PSCs by scalable thermal evaporation deposition. We used this YbOx buffer in the p-i-n PSCs with a narrow-bandgap perovskite absorber, yielding a certified power conversion efficiency of more than 25%. We also demonstrate the broad applicability of YbOx in enabling highly efficient PSCs from various types of perovskite absorber layer, delivering state-of-the-art efficiencies of 20.1% for the wide-bandgap perovskite absorber and 22.1% for the mid-bandgap perovskite absorber, respectively. Moreover, when subjected to ISOS-L-3 accelerated ageing, encapsulated devices with YbOx exhibit markedly enhanced device stability.

Abstract:

The use of a small organic molecular passivator is proven to be a successful strategy for producing higher-performing quasi-2D perovskite light-emitting diodes (PeLEDs). The small organic molecule can passivate defects on the grain surround and surface of perovskite crystal structures, preventing nonradiative recombination and charge trapping. In this study, a new small organic additive called 2, 8-dibromodibenzofuran (diBDF) is reported and examines its effectiveness as a passivating agent in high-performance green quasi-2D PeLEDs. The oxygen atom in diBDF, acting as a Lewis base, forms coordination bonds with uncoordinated Pb²⁺, so enhancing the performance of the device. In addition, the inclusion of diBDF in the quasi-2D perovskite results in a decrease in the abundance of low-n phases, hence facilitating efficient carrier mobility. Consequently, PeLED devices with high efficiency are successfully produced, exhibiting an external quantum efficiency of 19.9% at the emission wavelength of 517 nm and a peak current efficiency of 65.0 cd A-¹.

Abstract:

Mixed lead-tin (Pb:Sn) halide perovskites are promising absorbers withnarrow-bandgaps (1.25–1.4 eV) suitable for high-efficiency all-perovskitetandem solar cells. However, solution processing of optimally thick Pb:Snperovskite films is notoriously difficult in comparison with their neat-Pbcounterparts. This is partly due to the rapid crystallization of Sn-basedperovskites, resulting in films that have a high degree of roughness. Rougherfilms are harder to coat conformally with subsequent layers usingsolution-based processing techniques leading to contact between theabsorber and the top metal electrode in completed devices, resulting in a lossof VOC , fill factor, efficiency, and stability. Herein, this study employs anon-continuous layer of alumina nanoparticles distributed on the surface ofrough Pb:Sn perovskite films. Using this approach, the conformality of thesubsequent electron-transport layer, which is only tens of nanometres inthickness is improved. The overall maximum-power-point-tracked efficiencyimproves by 65% and the steady-state VOC improves by 28%. Application ofthe alumina nanoparticles as an interfacial buffer layer also results in highlyreproducible Pb:Sn solar cell devices while simultaneously improving devicestability at 65 °C under full spectrum simulated solar irradiance. Aged devicesshow a six-fold improvement in stability over pristine Pb:Sn devices,increasing their lifetime to 120 h