Important Consideration of Excitation Density in Photoluminescence Quenching Studies of Hybrid Perovskite Solar Cells
Robert Godin a, Daniel T.J. Bryant a, Jinhyun Kim a b, James R. Durrant a b
a Department of Chemistry, University of New Brunswick, P O Box 4400, Fredericton
b Center for Plastic Electronics, Imperial College London, London, SW7 2BZ, United Kingdom
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference Asia-Pacific Hybrid and Organic Photovoltaics (AP-HOPV17)
Yokohama-shi, Japan, 2017 February 2nd - 4th
Organizers: Tsutomu Miyasaka and Iván Mora-Seró
Poster, Jinhyun Kim, 020
Publication date: 7th November 2016

Photovoltaic cells based on hybrid perovskite absorbers have rapidly emerged as very promising for commercial applications since they have recently exceeded 20% solar power conversion efficiencies using low-cost solution-based processes.1 Mixed cation and halide hybrid perovskites possess superior optoelectronic properties, such as large absorption coefficient and long charge carrier diffusion length.2,3 Optimization of device structure and processing have led to a rapid increase in the device performance over the last 6 years.4, 5 Despite the remarkable achievements on pushing the efficiencies to new heights, huge gaps in knowledge of the absorption and emission semiconducting properties which may involve electron transitions from one energy state to another or other materials, a fundamental material property for energy conversion of photovoltaic devices, still have not been filled. Charge carrier dynamics are also a critical issue in not only perovskite materials but also for the fundamental understanding of solar cell devices in order to optimize device performance and approach the Shockley–Queisser efficiency limit of about 31% for 1.55 eV bandgap perovskite.6, 7

In this study, we investigated the excitation density dependence of the photoluminescence (PL) properties of methylammonium lead iodide (MAPI3)  perovskite films and the PL quenching efficiency (PLQE) of perovskite in junction with PEDOT:PSS and PC61BM, hole and electron acceptors respectively. Ground state optical spectroscopy in combination with femtosecond Transient Absorption Spectroscopy (fs-TAS) and time-resolved PL (tr-PL) allow us to unravel the excited state dynamics in these perovskite films and their interfaces with charge extracting layers. Our results demonstrate that the charge carrier density-dependant bimolecular recombination kinetics of MAPI3 compete with charge extraction at light fluxes approaching 1 sun. Ultimately, the excitation densities should be carefully considered when conducting PLQE experiments in order to mimic operating conditions and extract appropriate values of carrier sxtraction.



1.     NREL efficiency chart.

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4.     Y. Rong, Z. Tang, Y. Zhao, X. Zhong, S. Venkatesan, H. Graham, M. Patton, Y. Jing, A. M. Guloy and Y. Yao, Nanoscale, 2015, 7, 10595-10599.

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