Skip to content

Research at St Andrews

Interface limited hole extraction from methylammonium lead iodide films

Research output: Contribution to journalArticle

DOI

Open Access permissions

Open

Author(s)

Oskar Blaszczyk, Lethy Krishnan Jagadamma, Arvydas Ruseckas, Muhammad Tariq Sajjad, Yiwei Zhang, Ifor David William Samuel

School/Research organisations

Abstract

Small solar cells based on metal halide perovskites have shown a tremendous increase in efficiency in recent years. These huge strides in device performance make it important to understand processes such as accumulation and extraction of charge carriers to better address the scalability and stability challenges which have not been solved yet. In most studies to date it is unclear whether the limiting factor of charge extraction is charge transport in the bulk of the perovskite or transfer across the interface with the charge extracting layer, owing largely to the inaccessibility of buried interfaces. Separating bulk and interfacial effects on charge extraction can help the search for new charge extracting materials, improve understanding of charge transport in active layer materials and help optimise device performance; not only in the laboratory setting but also for commercial production. Here we present a method to unambiguously distinguish between bulk and interface effects on charge extraction dynamics which is based on time-resolved photoluminescence with different excitation density profiles. We use this method to study charge extraction from solution-deposited CH3NH3PbI3 films to NiO and PEDOT:PSS layers. We find that NiO shows faster hole extraction than PEDOT:PSS from the 300 nm thick perovskite film on the time scale of 300 ps which is independent of charge carrier density in the region of 1016-1017 cm-3 . The interface with NiO is found to only slightly limit charge extraction rate at charge densities exceeding 1016 cm-3 as the extraction rate is fast and does not decrease with time. This is in contrast to PEDOT:PSS where we find the charge extraction rate to be slower, decreasing with time and dependent on charge density in the region 1016-1017 cm-3 which we interpret as charge accumulation at the interface. Hence we find that charge extraction is severely limited by the interface with PEDOT:PSS. These findings are confirmed by transient absorption spectroscopy. A hole diffusion coefficient of D=(2.2 ±0.4) cm2/s was determined in the perovskite film that is independent of charge density. This indicates a band-like hole transport regime, not  observed for solution processed films before. Our findings stress the importance of interface optimization in devices based on perovskite active layers as there is still room for improvement of the hole extraction rate even in the case of the superior NiO layer.
Close

Details

Original languageEnglish
JournalMaterials Horizons
VolumeAdvance Article
Early online date9 Dec 2019
DOIs
Publication statusE-pub ahead of print - 9 Dec 2019

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. BODIPY derivatives with near infra-red absorption as small molecule donors for bulk heterojunction solar cells

    Marques dos Santos, J., Jagadamma, L. K., Latif, N. M., Ruseckas, A., Samuel, I. D. W. & Cooke, G., 16 May 2019, In : RSC Advances. 9, 27, p. 15410-15423 14 p.

    Research output: Contribution to journalArticle

  2. Engineered exciton diffusion length enhances device efficiency in small molecule photovoltaics

    Sajjad, M. T., Blaszczyk, O., Krishnan Jagadamma, L., Roland, T., Chowdhury, M., Ruseckas, A. & Samuel, I. D. W., 28 May 2018, In : Journal of Materials Chemistry A. 6, 20, p. 9445-9450 6 p.

    Research output: Contribution to journalArticle

Related by journal

  1. Hole delocalization as a driving force for charge pair dissociation in organic photovoltaics

    Matheson, A. B., Ruseckas, A., Pearson, S. J. & Samuel, I. D. W., 27 Feb 2019, In : Materials Horizons. Advance Article, 7 p.

    Research output: Contribution to journalArticle

  2. Systematic study of exciton diffusion length in organic semiconductors by six experimental methods

    Lin, J. D. A., Mikhnenko, O. V., Chen, J., Haji Masri, M. K. Z., Ruseckas, A., Mikhailovsky, A., Raab, R. P., Liu, J., Blom, P. W. M., Loi, M. A., Garcia-Cervera, C. J., Samuel, I. D. W. & Thuc-Quyen Nguyen, N. V., Mar 2014, In : Materials Horizons. 1, 2, p. 280-285 6 p.

    Research output: Contribution to journalArticle

ID: 263751537

Top