Improving/Boosting perovskite solar cells performance by using high quality TiO2/graphene-based nanocomposites as electron transport layer

International audienceIn the context of energy transition, development of efficient and cost-effective solar cells is a major objective to establish an optimal energy mix. The 3 rd generation of photovoltaic cells emerged to develop high efficient and low-cost cells combining the use of abundant materials and easy processes. Among them, photovoltaic cells based on perovskite materials demonstrated several significant advances with power conversion efficiencies up to 22% [1][2]. Nevertheless, efforts remain to be performed to improve the charge generation and collection of this kind of cell. Titanium dioxide mesoporous layer, while remaining an important component for perovskite structuration and electron transport in high efficiency devices, can indeed still promote charge trapping and recombination. As carbon nanostructures are good electron transporters, the use of TiO2/graphene nanocomposites seems to be a relevant strategy to reduce recombination phenomena and thus improve electron collection [3]. To achieve high quality of nanocomposites presenting well-controlled physical properties suitable for efficient and stable solar cells, we use the singular technique of laser pyrolysis, which enables to synthetize nanoparticles in a single step with a continuous flow. Attention is payed to the materials properties and their role and effect within solar cells. Tests were conducted with a MAPI-Cl perovskite deposited in a single-step following a reported procedure [4]. Our first results show a better electron injection efficiency from the perovskite to the mesoporous TiO2 layer with graphene, observed through steady-state photoluminescence spectroscopy. This tendency has been reinforced by devices performance that show larger photocurrents and smaller series resistance under standard illumination. More generally an increase in power conversion efficiency from 14.1 % to 15.1 % for these devices is reached for perovskite solar cells containing graphene in the mesoporous layer, demonstrating the benefit of the laser pyrolysis process for the production of high quality electron transport layer

Composites based on TiO2 and carbon nanostructures synthesized by laser pyrolysis: properties and applications in 3rd generation solar cells

International audienc

Nanocomposites TiO2/graphène pour le photovoltaïque à base de matériaux pérovskites : synthèse et propriétés

National audienc

TiO2/graphene-based nanocomposite as electron transport layer for perovskite solar cells: synthesis and properties

International audienc

Improving perovskite solar cells performance by using high quality TiO2/graphene-based nanocomposites as electron transport layer

International audienc

Composites based on TiO2_2 and carbon nanostructures synthesized by laser pyrolysis: properties and applications in 3rd^{rd} generation solar cells

International audienceThird generation solar cells emerged with the aim of developing efficient, easy processing and low cost solar cells. As titanium dioxide (TiO$_2$) is synthesized from abundant and inexpensive materials, it has been largely used as efficient electron transport layer in both Dye-Sensitized Solar Cells (DSSCs) and Perovskite solar cells. Still, efforts remain to be performed to improve photo-current generation in these cells, especially concerning the development of efficient and reliable charge transporting electrodes and selective contacts. Indeed, titanium dioxide layer presents defects that trap electrons and favor electron-hole pair recombination. Thanks to good physical properties of carbon nanostructures (carbon nanotubes, graphene), developing composites of TiO2 and carbon nanostructures as electron transport layer seems to be a relevant strategy for a better electron collection and therefore an optimal energy conversion in DSSCs or perovskite solar cells. We use the original technique of laser pyrolysis to synthesize composites of TiO$_2$ with carbon nanostructures, in order to achieve high quality of nanocomposites presenting well-controlled physical properties suitable for efficient and stable solar cells. We recently demonstrated a significant increase in efficiency for solid-state dye-sensitized solar cells by incorporating carbon nanotubes in the TiO$_2$ mesoporous electrode.[1] Our current research is focused on the synthesis and optimization of TiO2/graphene nanocomposites for perovskite solar cells. Particular attention is paid to material characterizations such as morphological and structural analysis as well as physical properties evaluation of the nanocomposites and their role and effects within solar cells

TiO2_2/graphene-based nanocomposites synthesized by laser pyrolysis: properties and application in perovskite solar cells

International audienceSince 2012, hybrid solar cells based on perovskite materials demonstrated several significant advances, with power conversion efficiencies now up to 22%, attracting strong interest within the scientific community [Zhou14, NREL efficiency table]. Still, efforts remain to be performed to improve photo-current generation, especially concerning the development of efficient and reliable charge transporting electrodes and selective contacts. Titanium dioxide mesoporous layer, commonly used as electron transport layer, presents defects that trap electrons and favor electron-hole pair recombination. Carbon nanostructures are good electron transporters, therefore the use composites of TiO$_2$ and carbon nanostructures seems to be a relevant strategy to reduce recombination phenomena and thus to improve electron collection [Wang15]. Here, we combine specific know-hows on both perovskite solar cells processing and production of nano-scaled materials by laser pyrolysis. Our aim is to develop high quality TiO$_2$/graphene nanocomposites with well-controlled physical properties for an optimal energy conversion.Particular attention is paid to material characterizations such as morphological and structural analysis as well as physical properties evaluation of the nanocomposites and their role and effects within solar cells. Our results show a larger dark current in presence of graphene, as well as larger photocurrents and smaller series resistance, traducing the benefits of graphene for a better charge collection in the device. More generally, a significant increase in power conversion efficiency is observed for perovskite solar cells containing graphene in the TiO$_2$ mesoporous layer

Study of TiO2/Graphene-based nanocomposites for perovskite solar cells: Synthesis and Properties

International audienc

Electrodeposited ZnO nanoparticles on vertically aligned carbon nanotubes (VACNTs) as promising charge extracting electrodes for halide perovskite devices

International audienceThis work presents an original nanostructured architecture for energy conversion applications based on vertically aligned carbon nanotubes (VACNTs). The developed approach consists in exploiting the directional charge transport provided by the VACNT-based network to efficiently extract photo-generated electrons in perovskite solar cells. High density, 20 µm-long carpets of VACNTs were synthetized by aerosol-assisted chemical vapor deposition (AACVD) process on aluminium substrates. We adapted the technique of electrodeposition, usually used for thin film elaboration, to easily decorate the carbon nanotubes by ZnO nanoparticles despite the high CNT density of the carpet, in order to reinforce the scaffold. Then, this dense nanostructured network was successfully infiltrated by a methylammonium lead iodide perovskite that crystallized homogeneously between the nanotubes and all along their length, from the bottom to the top. While this study is mainly focused on the materials nano-engineering aspect, the charge extraction ability of the system was tested by photoluminescence spectroscopy. A quantitative luminescence quenching is demonstrated, evidencing an efficient charge transfer between the perovskite and the VACNTs/ZnO electrode. These promising results led to the fabrication of fully working devices that demonstrated a diode-like electrical response, characteristic of a solar cell in the dark. Considering both the possibility to develop this architecture at the industrial scale and the obtained physical properties, electrodes based on VACNTs decorated by ZnO nanoparticles seems to be a relevant and promising candidate for efficient optoelectronic devices such as perovskite solar cells

Graphene / TiO2 composites synthesized in one-step by laser pyrolysis for improved charge extraction in perovskite solar cells

International audienc