Highly efficient large area flexible perovskite solar cells employing novel fullerene derivative as an electron transport layer
Taimoor Ahmad a b
a CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, Italy
b Saule Technologies, Mokotowska 1, Warsaw, 00-640, Warszawa, Poland
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Poster, Taimoor Ahmad, 025
Publication date: 25th November 2019


Amongst the emerging photovoltaic (PV) innovations, organic-inorganic halide perovskites attracted a lot of attention in the past few years. Perovskite PV technology is rapidly moving towards the commercialization stage Perovskite solar cells (PSCs) are particularly attractive due to their exceptional optoelectronic characteristics, low temperature processability which enables compatibility with flexible and light weight substrates and prospects of achieving ultra-low-cost manufacturing.

Fullerene derivative, [6,6]-phenyl C61 butyric acid methyl ester (PCBM), is commonly used as an electron transporting layer in planar heterojunction perovskite solar cells of p-i-n configuration. However, devices employing PCBM layer exhibit limited performance primarily due to non-radiative recombination at the perovskite/ETL interface, poor surface morphology of PCBM and commonly occurring fragmented film formation [1], [2]. In this study, we report a solution processed electron transport material based on novel fullerene derivative, [6,6]-Phenyl C61 butyric acid hexyl ester PCBC6, as a potential alternative to common electron selective compounds (solution processed or thermally evaporated) used in perovskite solar cells. Devices with PCBC6 exhibit improved power conversion efficiency, reaching 17.3 % on flexible substrates, with an active area of 1 cm². This is over 28 % higher than the best performance obtained for the cells employing PCBM. Compared to PCBM, enhanced photovoltaic performance is primarily attributed to significantly improved film morphology (higher solubility of PCBC6 due to long-chain alkyl group), which results in a better charge extraction and reduced non-radiative recombination at the perovskite/ETL interface. Solution-processed PCBC6 films were uniform, smooth and displayed conformal capping of perovskite layer. Furthermore, we characterized PCBC6 material for its electrical and optical properties. Additionally, we demonstrate facile scalable processing of this fullerene derivative. We fabricated flexible PSCs with ink-jet printed PCBC6, with efficiencies surpassing 16%, which highlights the prospects of using this material in an industrial process.

Finally, we present an effective doping strategy of PCBC6 layer. Enhanced charge carrier transport properties and denser film formation leads to an improvement of both, performance and long-term stability of flexible perovskite solar cells.

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