倒置平面p-i-n型钙钛矿太阳能电池(PSCs)具有良好的运行稳定性、可忽略的滞后效应，以及与p型硅底太阳能电池集成的潜力，可用于单片钙钛矿/硅串联光伏发电。特别是MA-free体系，消除了热不稳定的MA，有利于进一步延长薄膜和器件的长期稳定性。目前，基于倒置结构的CsFAPbI3体系的最高效率仅有23.5%，远低于n-i-p结构。而限制倒置MA-free体系效率的主要瓶颈是界面非辐射重组和非最佳的界面接触对载流子提取的阻碍。因此，通过对界面载流子动力学的深入研究和管理，合理设计上界面的优化是实现高性能倒置钙钛矿太阳能电池的必由之路。
鉴于此，上海交通大学陈俊超团队通过引入3-(氨基甲基)碘化哌啶(3AMP)、4-(氨基甲基)碘化哌啶(4AMP)、3-(氨基甲基)碘化吡啶(3AMPY)等二铵间隔阳离子和碘化环己基甲烷胺(CHMA)等单铵间隔阳离子处理钙钛矿/PCBM界面，系统地研究了以MA-free为优化成分的倒置PSCs中2D/3D异质结的电荷转移动力学。紫外光电子能谱和开尔文探针力显微镜结果表明，基于3AMP的DJ相2D覆盖层比CHMA的RP相2D覆盖层具有更匹配的能级景观和更平坦的表面电位波动。
飞秒瞬态吸收追踪的热载流子动力学表明，基于3AMP的纯DJ相2D覆盖层(n = 1)不仅可以用作界面缺陷钝化剂，还可以作为电子隧穿层以加速热载流子向PCBM的萃取。此外，为了进一步降低2D钙钛矿固有的量子限制效应对电荷转移的阻碍，通过准2D后处理(间隔阳离子+FAI)获得了具有更高n值的2D覆盖层。不幸的是，准二维覆盖层(n = 3, 4)在光照下不利于抑制Ag从电极向下迁移，尽管观察到短路电流(Jsc)略有升高。
最后，在开路电压(≈1.15 V)和填充系数(≈82.8%)增加的情况下，3AMP修饰的MA-free的倒置PSCs的功率转换效率达到了23.62%。最重要的是，在85°C加热720小时和最大功率点跟踪1000小时后，依旧保持初始PCE的89%和93.6%，表明DJ相纯2D钙钛矿覆盖层具有令人满意的热稳定性和操作稳定性。我们的工作为管理热载流子冷却和界面萃取动力学以制造超过Shockley-Queisser极限的热载流子太阳能电池提供了新的思路。
Figure 1. Surface morphology and structure. a) Chemical structures calculated dipole moments, and electrostatic potential mapping images of 3AMP, 4AMP, 3AMPY, and CHMA. b) Top-view SEM images of perovskite films for Control, 3AMP-, 4AMP-, 3AMPY- and CHMA-treated. c) XRD spectra of 2D perovskite based on 3AMP of n = 1, 2D perovskite based on CHMA of n = 1 and n = 2, Control, 3AMP-, 4AMP-, 3AMPY- and CHMA-treated perovskite films with different concentrations of 0, 1, 5, and 10 mg. d) 2D GIWAXS patterns of perovskite films for Control, 3AMP-, 4AMP-, 3AMPY-, and CHMA-treated. e) PCE statistical distribution of 20 Control, 3AMP-, 4AMP-, 3AMPY-, and CHMA-treated perovskite solar cells.
Figure 2. Physical and chemical properties of
the surface. XPS spectra of a) N 1s and b) Pb 4f in Control, 3AMP-treated, and
CHMA-treated perovskite films. c) Schematic energy-level diagrams of Control,
3AMP-treated, and CHMA-treated perovskite films. KPFM images and statistics of
surface potential distribution for d) Control, e) 3AMP-treated, and f)
CHMA-treated perovskite films. g) Hall effect measurement of Control,
3AMP-treated, and CHMA-treated perovskite films. h) Hall effect measurement
setup.
Figure 3. Hot-carrier cooling and extraction kinetics. Pseudo color plot of a) Control, b) CHMA, c) Control/PCBM, and d) 3AMP/PCBM perovskite films. Normalized pump-probe fs-TA spectra of e) Control, f) CHMA, g) Control/PCBM, and h) 3AMP/PCBM perovskite films. i) Average hot-carrier temperatures as a function of the delay time for Control, CHMA, Control/PCBM, and 3AMP/PCBM perovskite films. j) Energy loss rate of hot-carrier as a function of carrier temperature for Control, CHMA, Control/PCBM, and 3AMP/PCBM perovskite films. The solid lines are fittings using LO-phonon interaction model. Normalized TA dynamics probed at band-edges for k) Control and CHMA perovskite films and l) Control/PCBM and 3AMP/PCBM perovskite films. The photoexcitation energy is 3.10 eV and initial photoexcited carrier density is ≈5.07×1017 cm-3.
Figure 4. Photoelectric properties of PSCs. a) TPV and b) TPC of Control, 3AMP- and CHMA-treated PSCs. c) J-V curves of Control, 3AMP- and CHMA-treated PSCs measured in reverse scan and forward scan under AM 1.5G. d) EQE spectra and integrated Jsc of Control, 3AMP-, and CHMA-treated PSCs. e) The current density and PCE measured at the maximum power point for 300 s of Control, 3AMP-, and CHMA-treated PSCs. f) J-V curves of 3AMP+FAI and CHMA+FAI PSCs measured in reverse scan and forward scan under AM 1.5G.
Figure 5. Quasi 2D post-treatment. a) The schematic diagram of the upper surface structure of the perovskites after 2D and quasi-2D post-treatment. b) XRD spectra of 3AMP+FAI perovskite film and 3AMP-based 2D perovskite films of n = 2, 3, and 4. c) XRD spectra of CHMA+FAI perovskite film and CHMA-based 2D perovskite films of n = 2, 3, and 4. ToF-SIMS depth-profile analysis of the perovskite films treated by d) 3AMP, e) 3AMP+FAI, f) CHMA, and g) CHMA+FAI.
Figure 6. Ion migration and device stability.
Cross-section SEM and EDS images of aged samples (structure: ITO/ perovskite/
Ag) for a) Control, b) 3AMP, and c) 3AMP+FAI. d) Thermal stability of the
unencapsulated devices heating at 85 °C in N2 under dark. e) MPP tracking of
the unencapsulated devices in N2 under 1 sun illumination.
参考文献：
Yiting Zheng, et al. Managing Interfacial Hot-Carrier
Cooling and Extraction Kinetics for Inverted Ma-Free Perovskite Solar Cells
Over 23% Efficiency via Dion-Jacobson 2D Capping Layer, Adv. Funct. Mater., 2023.
https://onlinelibrary.wiley.com/doi/10.1002/adfm.202300576
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