Snaith group

Abstract:

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (V_OC ) are essential to further improve the tandem solar cells' performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V V_OC , reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%.

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:

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

Abstract:

Here we deposit the data and code necessary to generate the analysis found in our work. We have included: Simulation output from drift diffusion simulations; Photoluminescence imaging data (in a semi-raw and processed format); Outputs from our Bayesian analysis combining the two; and a clone of the code (from our public git repo) used to generate the analysis.