arXiv subjects

Jincheng Luo

Publications and source records attributed to Jincheng Luo.

3 recordsLinked to original sources

arXiv2026

Divergent Solid-state Conversion Pathways in Evaporated All-perovskite Tandem Solar Cells

Sequential thermal evaporation (sTE) is emerging as a solvent-free route to high-quality mid-bandgap perovskites, but its extension to mixed-halide wide-bandgap (WBG) and Sn-Pb narrow-bandgap (NBG) absorbers for all-perovskite tandem solar cells (TSCs) remains limited by an incomplete understanding of solid-state conversion. Here, using time-sliced ex situ analysis, we reveal divergent solid-state conversion mechanisms in sequentially evaporated WBG and NBG precursor stacks. In WBG stacks, formamidinium (FA)-containing species penetrate the inorganic template and Br/I redistribution precedes substantial three-dimensional perovskite formation. The photoactive phase then crystallizes from a chemically mixed reservoir, and absolute PbBr$_2$ thickness, rather than nominal PbBr$_2$/PbI$_2$ ratio, determines the final bandgap. In NBG stacks, by contrast, an early Pb-rich perovskite phase forms upon formamidinium iodide deposition, restricting further FA penetration into the buried SnI$_2$ precursor. Subsequent annealing promotes rapid lattice reorganization faster than Sn/Pb interdiffusion, leaving vertical compositional gradients. Guided by these insights, we develop sTE absorbers with bandgaps spanning 1.26-1.96 eV and demonstrate the first evaporated all-perovskite TSC, reaching a power conversion efficiency of 19.2%. Encapsulated tandems retain on average 80% of their initial efficiency after 1,200 h at 65 $^\circ$C (ISOS-D-2). These results establish bandgap-specific control of solid-state conversion as a design principle for sequentially evaporated perovskite tandem photovoltaics.

cond-mat.mtrl-sci↗

arXiv2024

Stabilizing Solution-Substrate Interaction of Perovskite Ink on PEDOT:PSS for Scalable Blade Coated Narrow Bandgap Perovskite Solar Modules by Gas Quenching

The development of scalable 1.25 eV mixed Pb-Sn perovskite solar modules by blade coating lags behind Pb-based perovskites due to limited understanding of solution-substrate interaction of the perovskite ink on PEDOT:PSS and subsequent gas quenching. To address this challenge, we systematically studied the wet film deposition and quenching process to better understand narrow bandgap perovskite film formation on PEDOT:PSS. We found, the wetting of Pb-Sn perovskite ink on PEDOT:PSS is highly unstable over relevant coating time scales, causing the contact angles to decrease rapidly from 42° to 16° within seconds. This instability leads to localized irregularities in the wet film, resulting in uneven solvent extraction and inhomogeneous nuclei density. As a result, rough perovskite films with voids at the buried interface are obtained. To overcome this problem, we developed a quasi-static wetting process by reducing the blade coating speed, thereby stabilizing the wetting behavior of Pb-Sn perovskite precursor ink on PEDOT:PSS. This optimized process facilitates the deposition of high-quality, void-free Pb-Sn perovskite films with uniform thickness over 8 cm of coating length using moderate (1.4 bar) N2 quenching. We achieved 20 % efficient narrow bandgap perovskite solar cells and mini-modules with 15.8 % active area efficiency on 15.9 cm2.

physics.app-ph↗

arXiv2022

High-Performance Flexible All-Perovskite Tandem Solar Cells with Reduced VOC-Deficit in Wide-Bandgap Subcell

Among various types of perovskite-based tandem solar cells (TSCs), all-perovskite TSCs are of particular attractiveness for building- and vehicle-integrated photovoltaics, or space energy areas as they can be fabricated on flexible and lightweight substrates with a very high power-to-weight ratio. However, the efficiency of flexible all-perovskite tandems is lagging far behind their rigid counterparts primarily due to the challenges in developing efficient wide-bandgap (WBG) perovskite solar cells on the flexible substrates as well as the low open-circuit voltage (VOC) in the WBG perovskite subcell. Here, we report that the use of self-assembled monolayers as hole-selective contact effectively suppresses the interfacial recombination and allows the subsequent uniform growth of a 1.77 eV WBG perovskite with superior optoelectronic quality. In addition, we employ a post-deposition treatment with 2-thiopheneethylammonium chloride to further suppress the bulk and interfacial recombination, boosting the VOC of the WBG top cell to 1.29 V. Based on this, we present the first proof-of-concept four-terminal all-perovskite flexible TSC with a PCE of 22.6%. When integrating into two-terminal flexible tandems, we achieved 23.8% flexible all-perovskite TSCs with a superior VOC of 2.1 V, which is on par with the VOC reported on the 28% all-perovskite tandems grown on the rigid substrate.

physics.app-ph↗