Soyun Park

Dry-Stamping-Transferred PC71BM Charge Transport Layer via an Interface-Controlled Polyurethane Acrylate Mold Film for Efficient Planar-Type Perovskite Solar Cells

The study of interlayers is important to enhance the performance of inverted perovskite solar cells (PSCs) because interlayers in PSCs align energy levels and improve charge transport. However, previous research into applying interlayers for PSCs has focused only on wet-coated methods, such as spin coating, to form the interlayer. Here, we fabricated planar-type PSCs deposited with a 6,6-phenyl-C71 butyric acid methyl ester (PC71BM) layer onto a CH3NH3PbI3 (MAPbI3) layer by stamping transfer through a relatively dry process condition. We demonstrated the effects of a stamping-transferred PC71BM layer using polyurethane acrylate (PUA), the surface energy of which was modified by 2-hydroxyethyl methacrylate (HEMA) to increase the transfer reproducibility. In PSCs with a stamping-transferred PC71BM layer, we observed an enhanced JSC and a comparable power conversion efficiency (PCE), which were caused by an enhanced coverage of the electron transport layer onto the MAPbI3 layer with preserved crystallinity, which occurs owing to improved electron mobility and exciton dissociation. The optimized device PCE through the dry-transferred PC71BM exhibited a JSC, fill factor, and PCE of 21.65 mA/cm2, 76.0%, and 15.46%, respectively. Moreover, morphological analysis and electrical measurements confirmed the improved durability of dry-stamping-transferred PSCs.

Counterbalancing of morphology and conductivity of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate based flexible devices

The importance of conductive polymer electrodes with a balance between the morphology and electrical conductivity for flexible organic photovoltaic properties has been demonstrated. Highly transparent PEDOT:PSS anodes with controlled conductivity and surface properties were realized by insertion of dimethyl sulfoxide (DMSO) and a fluorosurfactant (Zonyl) as efficient additives and used for flexible organic photovoltaic cells (OPVs) which are based on a bulk-heterojunction of polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7):[6,6]phenyl-C71-butyric acid methyl ester (PC71BM). We investigated the correlation between the electrical properties of PEDOT:PSS electrodes and their influences on the surface morphology of the active materials (PTB7:PC71BM). When the device was prepared from the PEDOT:PSS layer functioning as an anode of OPV through an optimized ratio of 5 vol% of DMSO and 0.1 wt% of fluorosurfactant, the devices exhibited improved fill factor (FF) due to the enhanced coverage of PEDOT:PSS films. These results correlate with reduced photoluminescence and increased charge extraction as seen through Raman spectroscopy and electrical analysis, respectively. The conductive polymer electrode with the balance between the morphology and electrical conductivity can be a useful replacement for brittle electrodes such as those made of indium tin oxide (ITO) as they are more resistant to cracking and bending conditions, which will contribute to the long-term operation of flexible devices.

Alignment of Cascaded Band-Gap via PCBM/ZnO Hybrid Interlayers for Efficient Perovskite Photovoltaic Cells

In this study, we investigated methylammonium lead iodide (MAPbI3)-perovskite solar cells (PSCs) with hybrid PC70BM/ZnO interlayers. The pristine device which had a PC70BM electron transport layer sandwiched between ITO/PEDOT:PSS/MAPbI3 and TiOx/Al electrodes exhibited PCE of 12.72% with a VOC of 0.98 V, Jsc of 18.41 mA/cm2, and FF of 71%. The new device with hybrid PC70BM/ZnO interlayers exhibited higher PCE of 14.17% with a VOC of 0.98 V, JSC of 20.08 mA/cm2, and FF of 72% due to the incorporation of ZnO nanoparticles in PC70BM electron transport layer (ETL) with high electron mobility and cascade band gap alignment. Here, we demonstrated that lower photoluminescence (PL) intensity of the device with hybrid interlayers could improve the JSC value of perovskite solar cells due to enhanced charge-generation efficiency. Contact resistance can be reduced by mixing ZnO nanoparticles with PC70BM electron transport layer without additional ZnO layer insertion.