Novel S-rich PbS QDs as a promising material for p-type layer in PbS QD solar cells

Dima Bederak^a, Nataliia Sukharevksa^a, Dmitry N. Dirin^b^,^c, Maksym V. Kovalenko^b^,^c, Maria A. Loi^a

^aUniversity of Groningen, The Netherlands, Nijenborgh, 4, Groningen, Netherlands

^bETH Zürich, Department of Chemistry and Applied Biosciences, Switzerland, Switzerland

^cEMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, Switzerland

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#NCFun19. Fundamental Processes in Semiconductor Nanocrystals

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Ivan Infante and Jonathan Owen

Poster, Dima Bederak, 249
Publication date: 18th July 2019

PbS colloidal quantum dots (QDs) are solution-processable semiconductors, which have been widely used in a variety of optoelectronic and photovoltaic devices. Despite the progress in PbS QD solar cells and reaching the power conversion efficiency of 12.5%,[1] the most efficient solar cells are still containing PbS treated with 1,2-ethanedithiol (EDT) as a p-type layer. A higher degree of p-doping of EDT-treated PbS QDs is achieved by exposing the film to air. Also, the lack of p-type materials with high doping has been recently identified as a performance limiting factor of PbS QD solar cells.[2] This is related to the most common synthetic method of the QD synthesis – hot injection. After the synthesis, PbS QDs have an excess of Pb atoms which result in dominant n-type electronic properties. Tuning the Pb/S ratio was predicted and shown to be a powerful strategy to control the degree and type of doping in PbS QD films.[3,4]

In this work, a new synthesis of S-rich PbS QDs and a ligand exchange protocol were developed. Investigation of thin-film field-effect transistors with these S-rich QDs revealed prevailing hole transport with linear mobility of 1∙10^-2 cm²/Vs without exposing devices to air.

References:

[1] Xu, J.; Voznyy, O.; Liu, M.; Kirmani, A. R.; Walters, G.; Munir, R.; Abdelsamie, M.; Proppe, A. H.; Sarkar, A.; García De Arquer, F. P.; et al. 2D Matrix Engineering for Homogeneous Quantum Dot Coupling in Photovoltaic Solids. Nat. Nanotechnol. 2018, 13, 456–462.

[2] Speirs, M. J.; Dirin, D. N.; Abdu-Aguye, M.; Balazs, D. M.; Kovalenko, M. V.; Loi, M. A. Temperature Dependent Behaviour of Lead Sulfide Quantum Dot Solar Cells and Films. Energy Environ. Sci. 2016, 9, 2916–2924.

[3] Kim, D.; Kim, D.-H.; Lee, J.-H.; Grossman, J. C. Impact of Stoichiometry on the Electronic Structure of PbS Quantum Dots. Phys. Rev. Lett. 2013, 110, 196802.

[4] Balazs, D. M.; Bijlsma, K. I.; Fang, H.-H.; Dirin, D. N.; Döbeli, M.; Kovalenko, M. V.; Loi, M. A. Stoichiometric Control of the Density of States in PbS Colloidal Quantum Dot Solids. Sci. Adv. 2017, 3, eaao1558.

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