新型钙钛矿型铁电体/莫特绝缘体异质结光伏结构的性能和机制研究

With the growing threats from energy and environment issues, developing clean energy technologies, as represented by solar energy, has attracted worldwide attention. Traditional Si-based solar cells, however, suffer from the efficiency bottleneck and their costs are still high. It is therefore of great importance to study new photovoltaic materials and new mechanisms, and to further develop high-efficiency, low-cost photovoltaic devices. This project for the first time proposes a photovoltaic heterostructure consisting of perovskite-structured ferroelectrics and Mott insulators. Ferroelectrics can provide a relatively high photovoltage and a driving force for the separation of photo-excited electron-hole pairs. Mott insulators, on the other hand, can show a suitable bandgap and a multi-exciton-generation effect, resulting in a boost in the number of photo-excited electron-hole pairs. The combination of these two perovskites may realize a high-efficiency photovoltaic effect, by taking advantages from both of them. In this project, we will first fabricate high-quality ferroelectric/Mott insulator double-layered heterostructures, and then characterize and optimize their photovoltaic properties. Next, we will reveal the photovoltaic mechanism through systematically studying the band structures, optical, ferroelectric and transport properties. Finally, we will investigate the possible effects of electric field and temperature on the photovoltaic output. This project may provide some innovative ideas and technical underpinnings for developing high-performance, multi-functional photovoltaic devices.

面对日益严峻的能源和环境问题，发展以太阳能为代表的清洁能源技术受到世界各国越来越多的重视。然而传统的硅系太阳能电池存在效率瓶颈且成本偏高，因此探索新型光伏材料和新机制进而开发高效、低成本光伏器件具有重要意义。本项目率先提出构建钙钛矿型铁电体/莫特绝缘体异质结，利用铁电体保证较高的光电压和提供光生电子-空穴对分离的驱动力，同时利用莫特绝缘体合适的带隙和多重激子效应提升光生电子-空穴对的数量，来实现高效光伏。具体研究内容包括制备高质量钙钛矿型铁电体/莫特绝缘体双层膜复合结构，表征并优化复合结构的光伏性能，再通过研究能带结构、光学、铁电、电输运等性能深入揭示复合结构的光伏机制，最后进一步探索电场、温度等因素对光伏输出的调控。本项目有望为开发新型高效、多功能光伏器件提供一些创新性的思路和技术基础。

面对日益严峻的能源和环境问题，发展以太阳能为代表的清洁能源技术受到世界各国越来越多的重视。然而传统的硅系太阳能电池存在效率瓶颈且成本偏高，因此探索新型光伏材料和新机制进而开发高效、低成本光伏器件具有重要意义。本项目拟构建钙钛矿型铁电体/莫特绝缘体异质结，利用铁电体保证较高的光电压和提供光生电子-空穴对分离的驱动力，同时利用莫特绝缘体合适的带隙和多重激子效应提升光生电子-空穴对的数量，来实现高效光伏。首先，我们分别制备了高质量铁电体Pb(Zr,Ti)O3 (PZT)和莫特绝缘体LaVO3 (LVO)薄膜，PZT薄膜体现优异的铁电性(剩余极化高达~75 μC/cm2)，而LVO薄膜则体现出较窄的带隙(~1.65 eV)和大量光生载流子(~5.4*1020 cm-3 @ AM1.5G, 100 mW/cm2)。然后，我们系统研究了不同LVO厚度的Pt/LVO/PZT/SrRuO3器件的光伏性能。其中，LVO厚度为24 nm的器件展现出最高的光电转换效率(PCE = ~0.01%)，并且光伏行为可翻转(可翻转的开路电压高达1.1 V)。相比于PZT单层膜器件，LVO/PZT双层膜器件的PCE提高了约5倍，这可归功于LVO层增加了光吸收，并且LVO/PZT界面内建场为光生载流子的分离提供了额外驱动力。而LVO/PZT双层膜器件能够体现良好的光伏可翻转性，是由于当LVO厚度低于24 nm时，极化仍然能够完全翻转。因此，我们的研究表明构建钙钛矿型铁电体/莫特绝缘体异质结是一种提升光伏效率同时保持良好的光伏可翻转性的重要手段。本项目有望为开发新型高效、多功能光伏器件提供一些创新性的思路和技术基础。