一、研究成果
全钙钛矿叠层太阳能电池是突破单结效率极限的重要方向，其中宽带隙顶电池会严重影响叠层器件的性能。传统自组装单分子层（SAM）在基底表面易呈平行堆积或倾斜排布，这容易产生界面覆盖不均、缺陷密度高、非辐射复合严重、能级匹配不佳等问题，导致宽带隙钙钛矿太阳能电池电压损失大、填充因子偏低等问题，这直接限制叠层电池的整体效率与稳定性。为此南京工业大学王芳芳&李仁志提出了直立SAM的界面工程策略，设计了一系列双锚定基团的咔唑基SAM分子（5,7-IDCz，5,11-IDCz和9,9-DCz）。由于吲哚并咔唑是一种刚性结构，且分子间的水平和垂直距离较小，导致5,7-IDCz和5,11-IDCz分子在溶液中容易发生聚集，并且在基底表面采取倾斜排布。而使用联咔唑为母核的9,9-DCz分子，通过双齿锚定和半柔性双咔唑结构，不仅可以有效的抵抗分子的聚集，而且在基底表面采取垂直直立组装，这提升了分子的表面覆盖率与堆积密度。并且双锚定基团一端锚定在基底形成稳定配位键，另一端高效钝化钙钛矿埋底界面，提高钙钛矿薄膜的结晶，有效降低缺陷密度与非辐射复合；优化能级排列，促进空穴提取，解决了宽带隙钙钛矿下界面缺陷多、电压损失严重的问题。最终基于9,9-DCz直立分子的宽带隙（1.77 eV）单结太阳能电池器件的效率达到了20.81%，经第三方认证为19.95%。且相应的全钙钛矿叠层太阳能电池效率达到28.59%，未封装器件在连续光照500小时后仍保持80%初始效率，展现出优异的运行稳定性。研究成果以“Standing up” SAMs for Efficient Wide Bandgap and All-Perovskite Tandem Solar Cells为题发表于Advanced Materials。
二、创新点
1.直立构型：9,9-DCz分子在基底表面呈直立分布，表面覆盖率大幅提升至79%。可形成均匀致密的自组装单层，为钙钛矿的生长提高良好的基底。
2.双齿锚定：双膦酸锚定基团一端锚定在ITO基底上，形成稳定的In O P配位键；另一端高效钝化钙钛矿埋底界面缺陷，降低非辐射复合损失，减少缺陷态密度，提高薄膜结晶质量。
3.能级匹配：溴原子修饰加深HOMO能级，与钙钛矿能级良好匹配，显著降低空穴注入势垒，显著提升器件的电压与填充因子（FF高达85.19%）。
4.高效率和高稳定性：基于9,9-DCz分子的宽带隙（1.77 eV）器件实现了20.81%的PCE，经第三方认证为19.95%。相应的全钙钛矿叠层器件获得了28.59%的PCE，在老化500小时候仍保持80%的初始效率。
三、数据概览
FIGURE 1 (a) MD simulations of the equilibrated SAMs on an ITO substrate, illustrating their final surface coverage. (b)DFT-calculated dimer models used to analyze intermolecular π–π stacking interactions of the dimers of SAMs. Key parameters shown include interlayer spacing and lateral translation distance. (c) DFT calculated Eb of the different SAMs at the full perovskite/SAM/ITO interface. (d) Schematic diagram of interface assembly simulation of different SAM molecules.
FIGURE 2 (a) DLS measures the size distribution of fresh and aged molecules in an ethanol solution. (b) XRR data showing the measured film thickness of each SAM on the ITO substrate, with an inset schematically comparing the measured with the theoretical molecular heights. (c) KPFM images visualizing the surface potential of the different SAM-coated ITO substrates (Scalebar:500nm). (d) Histograms of the CPD derived from KPFM maps. (e)Energy-level alignments diagram constructed from UPS measurements. (f) Molecular adsorption density calculation by CV measurements. (g) XPS spectra showing In3d peaks for ITO substrates coated with the different SAMs.
FIGURE 3 (a) Top-view SEM images of the buried interface of perovskite fabricated on different SAMs. Residual PbI2 impurities are highlighted by pink dashed circles (Scalebar: 300nm). (b) GIWAXS patterns of the buried interface of perovskite based on different SAMs. (c) KPFM images of the buried interface of perovskite based on different SAMs (Scalebar: 500nm). (d) XPS spectra of the buried perovskite films deposited on SAM-modified substrates: Pb 4f core-level spectra. (e) TRPL decay curves for perovskite films on different SAMs. (f) τdiff versus the logarithm of the PL intensity (ln(ΦPL)). (g) SCLC of the 4PACz, 5,7-IDCz, 5,11-IDCz, 9,9-DCz-based perovskite films.
FIGURE 4 WBG Single-Junction Devices: (a) Schematic of the WBG single-junction PSC architecture. (b) J–V curves of the champion WBG devices based on different SAMs. (c) IPCE spectra and corresponding integrated JSC curves for the champion WBG devices. (d) Statistical PCE distribution for WBG devices (n=30). (e) PLQY and (f) corresponding calculated QFLS for the WBG perovskite films on different SAMs. (g) Maximum-power-point tracking (MPPT) of unencapsulated WBG single-junction devices measured under one-sun illumination in N2. All-Perovskite Tandem Devices: (h) Schematic of the TSC architecture. (i) Cross-sectional SEM image of an all-perovskite TSC (Scalebar:1μm). (j) J–V curves and (k) EQE spectra for the champion 9,9-DCz-based all-perovskite TSC. (l) Statistic PCE distribution for TSCs with different SAMs (n=25). (m) SPO efficiency for the champion 9,9-DCz tandem device. (n) Long-term operational stability of the control and 9,9-DCz based unencapsulated tandem devices under 1-sun continuous illumination with MPPT in a glovebox.
论文地址：
https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.202521898
