: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

In inverted perovskite solar cells (PSCs), the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is a widely used electron transport material. However, a high degree of energy disorder and inadequate passivation of PCBM limit the efficiency of devices, and severe self-aggregation and unstable morphology limit the lifespan of devices. Here, we design a series of fullerene dyads FP-Cn (n = 4, 8, 12) to replace PCBM as an electron transport layer, where [60]fullerene is linked with a terpyridine chelating group via a flexible alkyl chain of different lengths as a spacer. Among three fullerene dyads, FP-C8 shows the most enhanced molecule ordering and adhesion with the perovskite surface due to the balanced decoupling between the chelation effect from terpyridine and the self-assembly of fullerene, leading to lower energy disorder and higher morphological stability relative to PCBM. The FP-C8/C60-based devices using Cs0.05FA0.90MA0.05PbI2.85Br0.15 as a light absorber show a power conversion efficiency of 21.69%, higher than that of PCBM/C60 (20.09%), benefiting from improved electron extraction and transport as well as reduced charge recombination loss. When employing FAPbI3 as a light absorber, the FP-C8/C60-based devices exhibit an efficiency of 23.08%, which is the champion value of inverted PSCs with solution-processed fullerene derivatives. Moreover, the FP-C8/C60-based devices show better moisture and thermal stability than PCBM/C60-based devices and maintain 96% of their original efficiency after 1200 h of operation, while their counterpart PCBM/C60 maintains 60% after 670 h.

Reducing Energy Disorder in Perovskite Solar Cells by Chelation.

Defect Passivation of Perovskite Films for Highly Efficient and Stable Solar Cells

Flexible perovskite solar cells (FPSCs) are prime candidates for applications requiring a highly efficient, low-cost, lightweight, thin, and even foldable power source. Despite record efficiencies of lab-scale flexible devices (19.5% on a 0.1 cm2 area), scalability represents a critical factor toward commercialization of FPSCs. Large-area automized deposition techniques and efficient laser scribing procedures are required to enable a high-throughput production of flexible perovskite modules (FPSMs), with the latter being much more challenging compared to glass substrates. In this work, we introduce the combined concept of laser scribing optimization and automatized spray-coating of SnO2 layers. Based on a systematic variation of the incident laser power and a comprehensive morphological and electrical analysis of laser-based cell interconnections, optimal scribing parameters are identified. Furthermore, spray-coating is used to deposit uniform compact SnO2 films on large-area (>120 cm2) plastic substrates. FPSCs with spray-coated SnO2 show comparable performance as spin-coated cells, delivering up to 15.3% efficiency on small areas under 1 sun illumination. When upscaling to large areas, FPSMs deliver 12% power conversion efficiency (PCE) and negligible hysteresis on 16.8 cm2 and 11.7% PCE on a 21.8 cm2 active area. Our perovskite devices preserved 78% efficiency when the active area increased from 0.1 to 16.8 cm2, demonstrating that our combined approach is an effective strategy for large-area manufacturing of perovskite devices on flexible substrates.

Laser-Scribing Optimization for Sprayed SnO2-Based Perovskite Solar Modules on Flexible Plastic Substrates.

Perovskite solar cells (PSCs) are being rapidly developed at a fiery stage due to their marvelous and fast-growing power conversion efficiency (PCE). Advantages such as high PCE, solution processability, tunable band gaps, and flexibility make PSCs one of the research hot spots in the energy field. Flexible PSCs (f-PSCs) owing to high power-to-weight ratios can be promising candidates to serve as power sources in mobile energy systems, space energy systems, portable functional devices, and so on. Herein, we give a review on recent progress in f-PSCs involving flexible substrates and flexible transparent electrodes, performance enhancement by optimizing functional layers, large-scale fabrication techniques, flexibility promotion strategies, and their potential applications. Furthermore, perspectives are discussed on the future development of f-PSCs. 

Flexible Perovskite Solar Cells: From Materials and Device Architectures to Applications

New Fullerene Derivative as an n‐Type Material for Highly Efficient, Flexible Perovskite Solar Cells of a p‐i‐n Configuration

Within a decade, perovskite solar cells (PSCs) leaped to the forefront of photovoltaic research, rapidly moving toward the industrial phase. Despite the impressive progress in technology developmen...

Barbara Wilk

Papers

New Fullerene Derivative as an n‐Type Material for Highly Efficient, Flexible Perovskite Solar Cells of a p‐i‐n Configuration

Green Solvent-Based Perovskite Precursor Development for Ink-Jet Printed Flexible Solar Cells