Category: Publications

Contribution: LPEM

Reference : Small. 2024, 2401505, https://doi.org/10.1002/smll.202401505 (Early view)

DOI : https://doi.org/10.1002/smll.202401505

Contacts : zhuoying.chen@espci.fr

 

Abstract :

The achievement of both efficiency and stability in perovskite solar cells (PSCs) remains a challenging and actively researched topic. In particular, among different environmental factors, ultraviolet (UV) photons play a pivotal role contributing to device degradation. In this work, by harvesting simultaneously both the optical and the structural properties of bottom-up-synthesized colloidal carbon quantum dots (CQDs), we provide a cost-effective means to circumvent the UV-induced degradation in PSCs without scarification on their power conversion efficiencies (PCEs). By exploring and optimizing the amount of CQDs and the different location/interfaces of the solar cells where CQDs are applied, we achieve a synergetic configuration where the photovoltaic performance drop due to optical loss is completely compensated by the increased perovskite crystallinity due to interfacial modification. As a result, on the optimized configurations where CQDs were applied both on the exterior front side as an optical layer and at the interface between the electron transport layer and the perovskite absorber, unencapsulated PSCs with PCEs > 20% are fabricated which can maintain up to ~ 94% of their initial PCE after 100 hours of degradation in ambient air under continuous UV illumination (5 mW cm^-2).

 

Left : Schematic illustrating the combined exterior and interfacial application of bottom-up synthesized carbon quantum dots (CQDs) in a functional PSC structure. Right : Unencapsulated PSC stability under continuous UV illumination measured on devices without (control) and with CQDs applied under different configurations in air. This work highlights a cost-effective means based on CQDs to circumvent the UV-induced degradation in efficient perovskite solar cells (PSCs) without scarification on their power conversion efficiencies.

 

Control of perovskite film crystallization and growth direction to target homogeneous monolithic structures

D. Zheng, F. Raffin, P. Volovitch, T. Pauporté

Nat. Commun. 2022, 13, 6655

https://www.nature.com/articles/s41467-022-34332-3

Contacts | daming.zheng@chimieparistech.psl.eu, thierry.pauporte@chimieparistech.psl.eu

Abstract | Getting performant organo-metal halide perovskite films for various applications remains challenging. Here, we show the behavior of solvent and perovskite elements for four different perovskites families and nine different initial precursor solution systems in the case of the most popular preparation process which includes an anti-solvent dripping-assisted spin coating of a precursor solution and a subsequent thermal annealing. We show how the initial solution composition affects, first, the film formed by spin coating and anti-solvent dripping and, second, the processes occurring upon thermal annealing, including crystal domain evolution and the grain growth mechan- ism. We propose a universal typology which distinguishes three types for the growth direction of perovskite crystals: downward (Type I), upward (Type II) and lateral (Type III). The latter results in large, monolithic grains and we show that this mode must be targeted for the preparation of efficient perovskite light absorber thin films of solar cells.

Sketch of process in spin-coating. Prolonging the spin-coating time or using an antisolvent accelerates the reverse movement of lead and sulfur to promote the formation of the perovskite phase

Sketch of process in Annealing. Using the GD-OES detection method, we obtained the growth models of the four perovskite film systems and realized the regulation of film growth by adding various additives. Take MAPI as example, without any additive, the film growth of MAPI is downward, After the addition of nanoparticles as additive, the film growth becomes lateral growth, which is the ideal direction for film growth.

Halide perovskites for photonic applications

M. Chamarro, C.R. Mayer, T. Pauporté, E. Drouard, H.-S. Nguyen, C. Seassal, S.C. Boehme, M.V. Kovalenko, E. Deleporte

Photoniques 2022, 116, 42-47

Abstract | Halide perovskites are a new class of semiconductors showing an incredible set of physical properties well- suited for a large range of opto-electronic applications. These physical properties can be easily tuned and adapted to the intended application by modifying the composition and the size of the material. Additionally, these materials are solution-processed at low temperature and ambient pressure, and contain earth-abundant elements. However, some important challenges remain : the presence of lead and the stability. In this paper, we present some outlines of these materials in several fields of opto-electronics, i.e. photovoltaics and light-emitting devices, such as LEDs, single-photon sources, lasers, and photonics.