【Small】四川大学彭强||突破20%效率大关！层层自组装有机太阳能电池喜获20.22%创纪录效率#

FIGURE 1 (a) Chemical structures of the two additives (A1 and A2) along with their corresponding electrostatic potential (ESP) maps and calculated molecular dipole moments. (b) Chemical structures of the donor polymer D18, and the non-fullerene acceptor L8-BO used in this work. (c) DSC thermograms of neat A1 and A2. (d) Normalized UV-vis-NIR absorption spectra of neat A1, A2, pristine D18, and D18 films blended with 10 wt.% A1 or A2. (e) Normalized UV-vis-NIR absorption spectra of the LbL-processed D18/L8-BO films without an additive and with A1 or A2 incorporated into the D18 layer.#

FIGURE 2 (a) Schematic illustration of the LbL fabrication process incorporating different solid additives. (b) PCEs of the D18/L8-BO-based LbL devices as a function of A1 or A2 dosage in the D18 layer. (c) J–V curves and (d) corresponding EQE spectra of the D18/L8-BO-based LbL devices without additives (control) and with 10 wt.% A1 or A2 in the donor layer.#

在光物理表征中，如图1所示，向D18中引入10 wt.%的添加剂后，薄膜的吸收光谱呈现出明显增强的0-0振动过渡峰强比，这清晰地表明同源添加剂能有效诱导D18聚合物链发生更强烈的分子间聚集与高度有序的排列。

光伏性能测试进一步验证了该形貌调控的优越性。如图2所示，采用层层法制备的太阳能电池器件在引入10 wt.%的A2添加剂后，填充因子大幅提升至80.46%，最终斩获了20.22%的最高光电转换效率，显著超越了对照组器件的19.23%和A1处理组的19.75%。此外，该器件还展现出优异的厚度耐受性，在300 nm的活性层厚度下仍能保持18.28%的高效率。

FIGURE 3 (a) 2D GIWAXS patterns of the LbL processed D18/L8-BO films without additives and with A1 or A2 incorporated into the D18 layer. (b) Corresponding 1D in-plane (IP) and out-of-plane (OOP) line-cut profiles. (c) Calculated crystal coherence lengths (CCLs) for the lamellar and π–π stackings. (d) Tapping-mode atomic force microscopy (AFM) height (left) and phase (right) images of the corresponding D18/L8-BO films.#

为了探究效率提升的微观机制，研究人员利用掠入射广角X射线散射和原子力显微镜对形貌进行了深度剖析。如图3所示，结晶特性分析表明添加剂并未改变D18固有的face-on取向，而是显著增加了晶体相干长度并缩小了 $\pi-\pi$ 堆叠距离。形貌图则直观地证明，经过A2处理的薄膜展现出更为连续、清晰的纳米级互穿纤维网络，这为电荷的高效传输奠定了形貌基础。

FIGURE 4 (a–c) 2D color plots of fs-TA spectra of the active layers. (d–f) The corresponding TA spectra of the active layers. (g) TA kinetics of the GSB signals of the active layers. (h) The column plots of τ1 and τ2 are estimated from fitting the TA kinetics. (i) TA kinetics of the ESA signals at 900 nm of the active layers.#

飞秒瞬态吸收光谱则进一步揭示了超快动力学过程。如图4所示，在激发电荷转移过程中，A2调控的薄膜激子激发的产生速度最快且扩散寿命最短。这强有力地证明形貌的激子离解效率得到了大幅提高，加快了激子向给受体界面的扩散与解离。

FIGURE 5 (a) Photogenerated charge extraction by linearly increasing voltage (photo-CELIV) curves of the OSCs. (b) _J_ph vs. _V_eff plots of the devices. (c) TPC and (d) TPV of the films. Photocurrent vs. the effective voltage of the _V_OC (e) and _J_SC (f) vs. Plight plots of the OSCs.#

最后，电荷输运与复合动力学表征进一步锁定了胜局。如图5所示，光致电荷抽取和空间电荷限制电流测试表明，A2处理后的器件拥有更高且更平衡的空穴和电子迁移率，其激子解离概率与电荷收集概率分别达到惊人的99.7%和99.0%。同时，瞬态光电压及光强依赖性测试也证实，A2引入所构建的完美微观结构极大地抑制了陷阱辅助复合。