IMPROVING PEROVSKITE SOLAR CELLS PERFORMANCE by USING HIGH QUALITY TiO2/GRAPHENE-BASED NANOCOMPOSITES as ELECTRON TRANSPORT LAYER
Raphaëlle Belchi a b, Aurélie Habert a, Nathalie Herlin-Boime a, Johann Bouclé b
a NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette, France
b Univ. Limoges, CNRS, XLIM, UMR 7252, F-87000 Limoges, France
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Poster, Raphaëlle Belchi, 013
Publication date: 23rd October 2018

In the context of energy transition, development of efficient and cost-effective solar cells is a major objective to establish an optimal energy mix. The 3rd 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].

Nevertheless, efforts remain to be performed to improve the charge generation and collection in this kind of cell. Titanium dioxide mesoporous layer, while remaining an important component for perovskite structuration and electron transport in these high efficiency devices, is responsible of charge trapping and recombination. These phenomena are two major loss mechanisms in this kind of cells. As carbon nanostructures are good electron transporters, the use of TiO2/graphene nanocomposites with a good interface between carbon and TiO2 seems to be a relevant strategy to reduce recombination phenomena and thus improve electron collection [2].

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. This technique already proved efficient for the production of TiO2 nanoparticles in anatase phase [3]. By adding graphene in the precursor, it was possible to obtain TiO2/graphene nanocomposites where TiO2 is strongly attached to the surface of graphene. Attention is payed to the materials properties and their role and effect within solar cells.

Tests were conducted with a chlorine-doped methylammonium lead iodide (MAPI-Cl) reference perovskite deposited in a single-step on TiO2 porous electrodes following a reported procedure [4]. Our first results show a better electron injection efficiency from the perovskite layer to the mesoporous graphene-doped TiO2, as revealed through steady-state photoluminescence spectroscopy. This trend is further reinforced by devices performance that evidences larger photocurrents and smaller series resistance under standard illumination in the presence of graphene. 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.

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