9:30 AM - EN08.04.03
The Next Big Thing—Single-Crystal Perovskite Solar Cells With 21% Power Conversion Efficiency
Bekir Turedi1,Zhaolai Chen1,Abdullah Alsalloum1,Chen Yang1,Xiaopeng Zheng1,Issam Gereige2,Ahmed Alsaggaf2,Omar Mohammed1,Osman Bakr1
King Abdullah University of Science and Technology1,Saudi Aramco2
Developments in perovskite photovoltaics dominantly rely on thin films of polycrystalline morphology. The record efficiency for PSCs which is 24.2%  is still far from their Shockley-Queisser (SQ) limit which is ~30.5% power-conversion efficiency (PCE) for methylammonium lead iodide (MAPbI3). Despite the marked efforts in improving polycrystalline perovskite films, they have significant parasitic non-radiative recombination due to their inherent grain size and surface defects. In contrast to polycrystalline perovskite films, single-crystal perovskites are orders of magnitude superior in terms of defect density, charge carrier mobility, and diffusion length. These advantages make the single-crystal perovskites a strong candidate to achieve their SQ limit. Unfortunately, there are a limited amount of studies on single-crystal perovskite solar cells (SC-PSC), most of which show inferior PCEs compared to polycrystalline counterpart. The highest PCE so far for SC-PSCs was reported in 2017 is 17.8% by Huang and co-workers.
Here, we achieved highly efficient SC-PSCs with PCEs reaching 21.1% and FFs of up to 84.3% (under 1-sun illumination). This is the first time for an SC-PSC to exceed the 20% PCE benchmark. These devices, based on a ~20 micrometers-thick MAPbI3 single-crystal active layer in an inverted p-i-n structure, set a new record for SC-PSC efficiency and a new potential benchmark for FFs that PSCs should aim for, which polycrystalline PSCs have struggled to achieve. We describe the crucial fabrication steps and measurement conditions required to achieve these high efficiencies. Additionally, our study is also answering an ongoing debate over the diffusion length of carriers in perovskite single-crystals. The different methods like 1D, SCLC, and 3D methods showed a diverse range from several microns to mm. Our work confirms the extraction length should be over 40 μm since the external quantum efficiency (EQE) is over 80% all over the absorbed spectrum. While there is still room for substantial interfacial optimization, our findings highlight the promise of single-crystals for advancing perovskite optoelectronic technology, which could be a parallel growing path to the one taken by their polycrystalline counterparts.
 NREL Best Research-Cell Efficiencies. 2019, https://www.nrel.gov/pv/cell-efficiency.html
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 Chen, Z.; Turedi, B.; Alsalloum, A.; Yang, C.; Zheng, X.; Gereige, I.; AlSaggaf, A.; Mohammed, O. F.; Bakr, O. M., Single-Crystal MAPbI3 Perovskite Solar Cells Exceeding 21% Power Conversion Efficiency. ACS Energy Letters 2019, 4, 1258-1259.