Foldable/Ultra-flexible Perovskite Optoelectronic Devices with Good Mechanical-Electrical-Moisture Stability for Extending Perovskite Applications

While perovskite materials have become promising candidates for highly performed optoelectronic devices, mechanical flexibility extends perovskite applications in emerging flexible/ foldable electronics. Additionally, solution-processed flexible/foldable perovskite SCs feature low cost, low carbon and low power consumption in production, shortened payback time, simple fabrication, and attractive power conversion efficiency (PCE) >20% (comparable to typical c-Si SCs). However, electrodes of organic/perovskite SCs such as widely adopted indium-tin-oxide (ITO) electrodes are formed by physical deposition methods (e.g., sputtering and thermal evaporation) which are high power consumption, large carbon footprint, and incompatible with high throughput production, thus hindering further development. Moreover, developing efficient flexible/foldable SCs with super-flexibility (foldability) is still challenging due to the poor mechanical durability of typical ITO electrodes.
We recently developed an in-situ solution-processed method (iSPM) to achieve a new class of foldable transparent electrodes (FTEs) composed of metal-oxide nanoparticles (MONPs) and silver nanowires (AgNWs) through the unique tri-system integration including (i) AgNW-AgNW, (ii) MONP-MONP, and (iii) AgNW-MONP systems [1]. Based on the new electrode, the foldable perovskite optoelectronic devices such as solar cells and LEDs with very good stability against multi-loading (mechanical-electrical-moisture) operation with folding radius as small as 0.75mm, humidity 85% and continuous electrical bias operations have been demonstrated. To further improve device performances, we have introduced several strategies to the perovskites including reconstruction of subsurface lattice for stable perovskite [2-3]. The PCE of the perovskite SCs can reach 25.8% [3]. We will design the functional side-branches of ligands of perovskite nanocrystals (PeNCs) for enhancing the electrical conduction and optimizing the spacing between the ligand functional groups and the surface pattern of PeNCs, resulting in effective synergistic passivation effect and significant improvements in PeLED efficiency and stability [4-7]. Meanwhile, through establishing ligand-termination surface structure on perovskites with anchoring points and polymeric soft chains on perovskites beyond the corresponding functional group-only or polymer-only strategies in reducing Young’s modulus, we demonstrated high efficiency and mechanical stabile flexible PeLEDs [7]. Overall, the efficiency and stability of the foldable/ultra-flexible red-green-blue (RGB) perovskite LEDs can be significantly improved by comprehensively designing the ligand structures.

[1] J. Kim, W.C.H. Choy, et al, Nature Commun., 15, 2070, 2024; [2] Z.W. Gao, W.C.H. Choy, et. al, Joule 8, 1, 2024; [3] Z.W. Gao, W.C.H. Choy, et. al, Nature Photonics, accepted. [4] B. Lyu, W. Choy, et. al., ACS Energy Lett., 8, 577,2023; [5] D. Li ,W. Choy, et. al., ACS Energy Lett., DOI:acsenergylett.4c00881; [6] B. Lyu, W. Choy, et. al., Angewandte Chemie, in press; [7] C. Liu, W. Choy, et. al., Adv. Funct. Mater., 2024, 2404791.