Sashil Chapagain1,Peter Armstrong1,Thad L Druffel1,Craig Grapperhaus1
University of Louisville1
Sashil Chapagain1,Peter Armstrong1,Thad L Druffel1,Craig Grapperhaus1
University of Louisville1
Flexible perovskite solar cells (f-PSCs) on plastic substrate have drawn appreciable attention as they have high power-per-weight and potentially wide applications in portable and wearable electronics, aviation, integration in vehicles and buildings, and aerospace. However, the power conversion efficiencies of these f-PSCs are still far below conventional perovskite solar cells on glass substrate. In this study, we investigated the direct deposition of a metal oxide electron transport layer on the top of perovskite for the high-performance f-PSCs. Metal oxide electron transport materials are inexpensive and scalable as compared to their organic counterparts. However, deposition of fully solution-processed metal oxide on perovskite to fabricate f-PSCs is limited by solvent incompatibility of typical metal oxide dispersion media with the underlying perovskite layer and the high processing temperature of metal oxides nanoparticles. Here, we synthesized SnO<sub>2</sub> nanoparticles using the sol-gel method and functionalized them with acetate through ligand exchange allowing their dispersion in anhydrous ethanol. Additionally, we investigated <i>in situ</i> yttrium doping of SnO<sub>2</sub> during synthesis. Nonaqueous dispersions of pristine and yttrium doped SnO<sub>2</sub> were directly deposited on the perovskite by blade coating followed by air knife treatment. There was no detectable damage to the underlying perovskite layer as evidenced by x-ray diffraction and scanning electron microscopy. Photoluminescence spectroscopy and device performance statistics confirm superior electron extraction by yttrium doped SnO<sub>2</sub> as compared to pristine one. After yttrium doping, the champion power conversion efficiency was increased above 18% from 15%, which is unprecedented for an inverted device in flexible ITO-PET substrate employing SnO<sub>2</sub> as an ETL. This work highlights the possibilities of the scalable deposition of fully solution-processed metal oxide charge transfer layers directly on the perovskite to achieve highly efficient large-area flexible perovskite solar cells