Submitted by Pooja Pandey on Thu, 16/02/2023 - 11:09
Researchers at the Cavendish Laboratory have found that mixed-metal perovskite devices display significantly higher long-range mobility and greatly suppressed ionic screening effects when compared to the more popular pure-lead-based devices. The key conclusions derived from this work will propel further development of the mixed metal systems for a variety of applications, including solar cells, LEDs, detectors and transistors.
Inspired by this work, we hope that various alternative molecular and interfacial doping strategies will now be devised to achieve similar control over ion migration in other similar materials systems, including pure-Pb-based perovskites. Prof. Henning Sirringhaus
Metal halide perovskites have dramatically disrupted the research on next generation optoelectronic devices including solar cells, light emitting diodes (LEDs) and X-ray detectors. However, these soft electronic-ionic semiconductors are made of ions that can move in response to external stimuli, such as light, heat and voltage, thereby creating severe ionic migration effects that undermine the device performance and their operational stability.
Researchers at Cambridge’s Cavendish Laboratory and Department of Chemical Engineering and Biotechnology have now found a way to mitigate such undesirable effects by using simple composition engineering with lead and tin, thereby allowing the inherent defect and transport physics of these mixed-metal systems to be explored using a reliable and popular platform of field effect transistors (FETs). Reported in Nature Materials, these findings now places halide perovskites in the same league as other emerging semiconducting materials, such as organics, metal oxides and 2D materials, where FETs are routinely employed to understand their charge transport mechanisms.
Mixed lead-tin perovskites are ideal low bandgap absorbers for bottom-subcells in all-perovskite tandem solar cells. While these materials have been intensively studied for solar cell applications and their short-range transport properties probed using various non-contact spectroscopic techniques, their long-range transport properties remained elusive until now. Using a combination of experimental observations and theoretical calculations, researchers have now demonstrated that equimolar proportion of lead and tin in the hybrid perovskite composition can result in a high FET hole mobility of 5 cm2/Vs, which is promising for solution processed 3D perovskite thin films. These mixed lead-tin FETs also show substantially reduced ionic screening effects when compared to their pure-Pb counterparts, thereby significantly alleviating the longstanding challenge of ionic screening effects in perovskite FETs.
“This is a big leap forward in the development of perovskite FETs,” said Dr. Satyaprasad P. Senanayak, Royal Society visiting Fellow at Cavendish and Assistant Professor at NISER, India and co-first-author of the study. “With the demonstration of such outstanding and reliable p-type FETs, these semiconductors might now find applications as well in flexible electronic devices.”
Despite years of research on tin-containing halide perovskites, the inherent chemical instability of Sn2+ ions to oxidation under inert or atmospheric conditions and the formation of a large density of intrinsic defects have caused scepticism around the applicability of these materials in next-generation devices. “Despite their stability issues, that these inherently doped mixed metal perovskite systems showed such surprising charge and ionic transport properties highlights the fact that there are always two sides to a coin and so is the case for mixed lead-tin perovskites,” said Krish Dey, PhD candidate at the Cavendish Laboratory and co-first-author of the study.
Researchers believe that the key conclusions derived from this work will propel further developments of these mixed metal systems for a variety of applications, including solar cells, LEDs, detectors as well as transistors.
“These halide perovskite materials continue to surprise, and this work draws us a key step closer to understanding their fundamental transport properties – particularly in these doped, mixed-metal versions” said Professor Sam Stranks, one of the senior corresponding authors of the work.
“Inspired by this work, we hope that various alternative molecular and interfacial doping strategies will now be devised to achieve similar control over ion migration in other similar materials systems, including pure-Pb-based perovskites”, said Professor Henning Sirringhaus, senior corresponding author.
Reference: Senanayak, S.P., Dey, K., Shivanna, R. et al. Charge transport in mixed metal halide perovskite semiconductors. Nat. Mater. 22, 216–224 (2023). https://doi.org/10.1038/s41563-022-01448-2
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