Direct measurement of the exciton binding energy and effective masses for charge carriers in organic–inorganic tri-halide perovskites
By A. Miyata, A. Mitioglu, P. Płochocka, O. Portugall, Jacob Tse-Wei Wang, S. Stranks, H. Snaith, R. Nicholas. Nature Physics, 2015
1,821 citations recorded by the source corpus.
Solar cells based on the organic–inorganic tri-halide perovskite family of materials have shown significant progress recently, offering the prospect of low-cost solar energy from devices that are very simple to process. Fundamental to understanding the operation of these devices is the exciton binding energy, which has proved both difficult to measure directly and controversial. We demonstrate that by using very high magnetic fields it is possible to make an accurate and direct spectroscopic measurement of the exciton binding energy, which we find to be only 16 meV at low temperatures, over three times smaller than has been previously assumed. In the room-temperature phase we show that the binding energy falls to even smaller values of only a few millielectronvolts, which explains their excellent device performance as being due to spontaneous free-carrier generation following light absorption. Additionally, we determine the excitonic reduced effective mass to be 0.104me (where me is the electron mass), significantly smaller than previously estimated experimentally but in good agreement with recent calculations. Our work provides crucial information about the photophysics of these materials, which will in turn allow improved optoelectronic device operation and better understanding of their electronic properties. Direct measurement of the exciton binding energy shows that the impressive performance of perovskite solar cells arises from the spontaneous generation of free electrons and holes after light absorption.
Subfields: Electrical and Electronic Engineering
View Paper: https://www.semanticscholar.org/paper/8fae3683f5c440066565f9cc5c5f9ae8cf4e965a
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Citations in the corpus
- Optical transitions in hybrid perovskite solar cells: Ellipsometry, density functional theory, and quantum efficiency analyses for CH3NH3PbI3 (2015, background): “For the E0 transition, the non-excitonic character has already been confirmed [5,66,67].”
- Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites (2017, methodology): “We thus propose three approaches to continue to improve the operational stability of perovskite LEDs: (1) use more bulky organic ligands to stabilize the surface and impede ion migration; (2) decrease turn-on voltage through further interface engineering such that devices operate at lower voltages; ”