| 초록 |
Recently, the trend in inverted hybrid perovskite solar cells has been to replace the commonly used PEDOT:PSS layer with NiOx films, which has proven to be an efficient HTL. However, the majority of reported solution-processed NiOx films have generally been prepared by sol-gel precursor solutions or nanoparticles dispersed in polar organic solvents that undergo a high-temperature thermal annealing process (＞300 °C), which increases fabrication cost and is unfavorable for flexible devices or large-scale manufacturing. In addition, most processes utilize spin-coating, a deposition technique that must eventually be replaced due to its limitation for large-area deposition and problems with uniformity. We report, for the first time, e-beam evaporation as a low-temperature, vacuum process for the deposition of NiOx hole transport layers for hybrid perovskite solar cells. Device characterization shows that efficiency is on par with solution-processed methods, the highest efficiency at 15.4 % with no obvious hysteresis. Compared to spin-coated NiOx-based perovskite solar cells, the e-beam evaporated NiOx-based perovskite solar cells show relatively lower current density but higher fill factor. These differences are explained by the increase in Ni3+:Ni2+ ratio for e-beam evaporated NiOx where the Ni3+ ions are responsible for both electrical conductivity, leading to higher fill factor, and coloring in the NiOx films, leading to lower transmittance and hence lower short circuit current density. In addition, e-beam evaporated NiOx-based perovskite solar cells show a highly consistent efficiency distribution between the different cells in one device, which relates to the uniformity of the NiOx thin film, and also shows greater reproducibility over several devices compared to those of spin-coated NiOx-based perovskite solar cells. Finally, e-beam evaporated NiOx has the additional advantage of being a low-temperature deposition process and being applicable over large areas. This work, therefore, represents a significant step towards large-area PVSCs where e-beam evaporation can be used for the low-temperature, uniform deposition of charge transport layers such as NiOx. |
