高效率两端子双节钙钛矿/有机叠层太阳能电池的制备与性能研究

Metal halide perovskite semiconductors, thanks to their feature of tunable bandgap can be employed to fabricate tandem solar cells paired with not only perovskite themselves but also other dissimilar photovoltaic semiconductors, which holds potential to break the Shockley-Queisser radiative efficiency limits for single-junction cells. However, the highest efficiency of two-terminal double junction perovskite/organic tandem solar cells is merely 15.13%, which is primarily attributed to low efficiencies of the single-junction subcells and undesirable interface property between interconnecting layer and charge transport layers, consequently resulting in low short-circuit density and high energy loss of the tandem device. Therefore, we propose to fully improve the performance of subcells by means of preparing high-quality perovskite/organic films, utilizing proper charge transport layers with aligned energy levels and heterojunction interfacial engineering. Finally, we explore to fabricate highly efficient two terminal double junction perovskite/organic tandem solar cells by employing the tunneling recombination layer with high optical transmittance and conductivity. We intend to systematically engineer the interfacial properties between perovskite/organic absorber layer, carrier recombination layer and charge transport layers, and the corresponding impacts on the tandem device performance, and illuminate the mechanism of charge carrier dissociation, transportation and recombination in the perovskite/organic tandem solar cells, which will lay the foundation of further improving the efficiency of perovskite/organic tandem solar cells and pushing them toward flexible device application.

金属卤化物钙钛矿半导体材料由于其带隙可调特性，可与钙钛矿材料本身以及其它类型半导体光伏材料耦合制备叠层电池，有望突破单节太阳能电池的Shockley-Queisser辐射效率极限。然而，两端子双节钙钛矿/有机叠层电池最高效率仅有15.13%，其主要原因为单节子电池效率不足，以及载流子复合层/电荷传输层的不良界面导致叠层电池的短路电流密度过低、能量损耗过高。因此，本项目将从制备高质量钙钛矿/有机薄膜、选择能级匹配的电荷传输层到各种异质结界面性质调控入手全面提升优化单节子电池性能；制备光学透过率高、导电性能优良的隧道复合层，最终制备高效率两端子双节钙钛矿/有机叠层太阳能电池。拟将系统调控钙钛矿、有机吸光层/电荷传输层，隧道结复合层/电荷传输层等界面性质以及对叠层电池的性能影响，探明叠层太阳能电池中载流子分离、输运以及复合机制, 为进一步提升钙钛矿/有机叠层电池效率，及其在柔性方向发展奠定基础。

钙钛矿/有机叠层太阳能电池，由于其处理溶剂的正交性，带隙可调性以及无限制的分子设计性，被视为最有发展前景的钙钛矿相关叠层电池技术之一。然而，受限于有机光伏材料的吸光能力，以及全蒸镀制备的内部连接层较大的光学损耗，使得钙钛矿/有机叠层太阳能电池的性能大幅度落后于其他类型的钙钛矿相关的叠层电池。通过本项目的支持，我们通过调控优化有机三基元组分比例、利用2PACz单分子层钝化空穴传输层MoOx，制备的单节有机太阳能电池具有较低的非辐射复合度，比较平衡的电荷传输匹配度以及在界面处较低的肖特基势垒。制备的有机薄膜厚度300 nm的太阳能电池光电转换效率达到了18.08%，认证效率17.8%。其中，电池的短路电流密度达到了28.48 mA cm-2，填充因子达到了75.11%。该效率为目前厚膜有机太阳能电池的最高效率。之前报道的钙钛矿相关的叠层太阳能电池的中间连接层基本都是采用磁控溅射或者原子力沉积的方法制备。但是磁控溅射的方法容易对刚性偏软的钙钛矿薄膜造成损伤；而原子力沉积的方法耗时较长，降低了叠层器件的整体制备时间。因此，我们发展了一种利用传统简单的热蒸镀方式蒸镀金属银与氧化铟锡（ITO）的混合物作为叠层器件的中间复合层，此方法得到的复合层展现出了较低的光学与电学损耗。最终制备的钙钛矿/有机叠层太阳能电池达到了24.3%的光电转换效率，认证效率24.0%。在一个太阳光照下，器件经过350小时光照后，效率仍能保持初始效率的80%。该项目取得的成果使钙钛矿/有机叠层太阳能电池的发展达到了一个新的转折点，希望能为该领域的发展提供更加巨大的势头。