施淋枫，袁皓，孟祥川,2，胡笑添,2，陈义旺,2,3

大面积柔性有机太阳电池：器件设计与印刷技术

施淋枫1，袁皓1，孟祥川1,2，胡笑添1,2，陈义旺1,2,3

（1.北京大学长三角光电科学研究院，江苏 南通 226010；2.南昌大学 化学化工学院/高分子及能源化学研究院（IPEC），南昌 330031；3.江西师范大学 高等研究院/氟硅能源材料与化学教育部重点实验室，南昌 330022）

为研究者提供OSCs制造技术相关的全面见解和最新进展，分析现有的技术瓶颈和无法解决的规模效率损失，以获得可扩展和可打印的大面积光伏组件。从功能层材料的选择、印刷工艺研究现状和大面积效率损失等方面展开综述，重点阐述柔性高效大面积有机光伏器件印刷制备的技术难题。文中将进一步推动可印刷有机半导体材料在下一代清洁能源中的集成应用，并在可穿戴电子、光伏建筑一体化和物联网等应用领域引起广泛关注。

有机光伏电池；模组化设计；柔性器件；印刷技术

与传统光伏器件相比，可柔性是有机太阳电池（OSCs）最突出的优势，其显示出巨大的商业潜能。目前已有研究工作者在界面/活性层合成，器件结构设计，透明电极修饰和印刷技术创新等领域开展广泛研究，单结OSCs的最大光电转换效率（PCE）已超过19%，符合商业化应用标准，但印刷技术的合理选择、大面积印刷的性能损失和柔性组件的结构设计仍然是限制柔性OSCs商业化的瓶颈。关于可印刷柔性大面积OSCs的打印技术/功能材料以及光伏组件的效率损失分析的最新进展，目前还没有详细的综述。文中综述柔性有机太阳电池（OSCs）和组件（OSMs）的各种印刷技术、性能损失和模块化设计的最新研究进展，为可印刷和大规模有机半导体材料提供了一站式参考。

1 简介

与晶体硅太阳电池和基于无机半导体材料的薄膜太阳电池相比，有机太阳电池（Organic Solar Cells，OSCs）具有质轻、价廉、可溶液加工和可柔性等诸多优点，在可穿戴电子设备的集成设计和与卷对卷（Roll-to-Roll，R2R）大面积印刷技术的适应性上表现出巨大潜能[1-5]。近年来，随着有机光伏材料和器件结构的飞速创新，通过旋涂法制备的刚性OSCs的功率转换效率（Power Conversion Efficiency，PCE）有了明显提高，目前最佳PCE值已达到19%以上，这说明了其已具有一定的商业化价值[6-12]。此外，随着各种R2R印刷方法的发展和研究的深入，印刷OSCs的PCE也已接近17%，这进一步验证了溶液印刷光电器件的可行性[13-17]，因此，柔性可印刷OSCs在可穿戴能源、便携式电子设备和异形显示设备中具有广阔的应用前景，这引起了人们的广泛关注。

图1显示了柔性OSCs的器件结构以及基于刚性和柔性衬底、大面积和小面积衬底的OSCs的PCE值发展趋势[13,15,18-100]。如图1a所示，常规的OSCs器件一般包括顶部背电极层、p型有机半导体给体材料和n型有机半导体受体材料组成的光敏层，以及底部透明电极层，同时，为了保证足够的电荷收集和传输，在透明电极层/背电极层与光敏层之间常使用两层缓冲层材料[101-102]，因此，需要从上述5层中优化OSCs的整体机械力学稳定性（包括耐弯折、耐拉伸、扭转、皮肤亲和性等）。首先，柔性透明电极会显著影响OSCs的光电性能和力学稳定性。完美的透明电极需要具备以下特点：理想的方块电阻、合适的透光率、光滑的表面粗糙度、足够的机械强度和良好的热稳定性[103-107]。然而，当前高效OSCs的透明电极通常是脆性的氧化铟锡（Indium Tin Oxide，ITO）材料，该材料不符合柔性OSCs的制备要求。因此，为了能找到在极端弯曲条件下有良好综合性能的柔性透明电极，人们在制备ITO电极替代品方面做了许多研究工作，在这些替代品中，最具代表性材料有银纳米线或网格、超薄金属层、碳基材料和导电聚合物等[72,107-118]。另外，OSCs光电性能的进一步优化还取决于高性能耐弯折缓冲层和光敏层材料的发展。因出色的空穴和电子选择和收集能力，聚（3,4–乙二氧噻吩）∶聚（苯乙烯磺酸盐）（PEDOT∶PSS）阳极缓冲层和聚电解质阴极缓冲层是最常用于柔性OSCs的材料[72,119-127]。此外，具有光伏性能可设计性和厚度不敏感性的新型给体/受体材料的分子设计和合成为柔性OSCs的发展提供了必要的基础[6,7,9,10,12,31,61-78]。迄今为止，柔性OSCs的最佳PCE值已超过16%（基于柔性银纳米线衬底），该PCE已初步达到了光伏器件商业化的最低标准[74]。总之，进一步开发高性能缓冲层和具有理想柔性、环境稳定性、最佳形貌和相分离结构的光敏层材料对于发展柔性OSCs来说仍有重要意义[128-139]。

图1 有机太阳电池结构及性能

为了满足OSCs长远应用的实际需求，相应的大面积器件制备工艺也很重要。与发展较好的小面积OSCs的相比，各种R2R印刷技术制备的大面积OSCs效率损失显著，尤其是在柔性衬底上[75,77,140-144]。2009年，Krebs等[145-147]总结了不同制备OSCs的成膜方法，他们指出旋涂技术不适合大规模柔性OSCs的生产，并介绍了一系列用来制备柔性大面积OSCs的印刷技术。这些技术主要有半月板刮涂、狭缝挤出印刷、凹版印、丝网印刷、喷墨打印等。最近，Li等[148]报道了一种高效的顺序沉积制备准平面异质结OSCs的方法，即通过基于非卤化溶剂体系的连续沉积来制备可印刷OSCs，获得了16.77%的PCE值。Hou等[83]采用半月板刮涂技术，在1.0 cm2面积上基于卤素或非卤素溶剂体系制备的刚性OSCs效率达到15.5%或10.6%。Min等采用逐层刮涂的策略在PM6:Y6系统上制备OSCs，获得了16.35%的PCE。此外，11.52 cm2的太阳电池组件获得了11.86%的记录性PCE，其几何填充因子（Geometrical Fill Factor，GFF），也就是组件对于入射光的实际有效利用面积超过90%[81]。很容易发现，从实验室小规模制备到工业大面积生产，如何保持优良的光伏特性一直是OSCs商业化转变的致命弱点。因此，在旋涂或印刷过程中探索本体异质结(BHJ) OSCs的形貌演化机制很有必要。Chen等[15]证实了通过狭缝挤出印刷制备可将柔性OSCs扩展到大面积有机太阳电池组件（15 cm2），且不会造成明显的性能损失。他们首先利用在旋涂和狭缝挤出印刷技术中的剪切冲量来调整富勒烯/非富勒烯OSCs体系有机光敏层的形貌演变，并获得了狭缝挤出印刷和旋涂之间的定量剪切冲量转换因子。与此同时，对于PTB7–Th:PC71BM和PBDB–T:ITIC光敏层，基于1.04 cm2的柔性狭缝挤出印刷OSCs的PCE分别达到9.10%和9.77%。在满足机械稳定性和制备重现性的前提下，15 cm2柔性有机太阳电池组件（Organic Solar Modules，OSMs）的效率可达8.90%。与小面积OSCs的制备相比，大面积OSCs印刷制备过程中的形貌演化控制规律和印刷技术都发生了变化，因此有必要对基于各种印刷方法制备的柔性大面积光电器件进行全面回顾。

文中综述了大面积OSCs的研究现状和高效印刷制备方式的发展现状，主要集中在以下两方面。

1）用于大面积印刷制备的柔性有机光伏材料。为了实现OSCs和OSMs的高质量大面积印刷，形貌和相分离的可控性研究以及活性层的厚度不敏感设计是必不可少的，相关研究已被广泛报道，包括富勒烯受体体系、非富勒烯受体体系、全聚合物体系和三元共混体系等。

2）大面积制备OSCs的印刷方法。很多可大面积化的沉积制备技术已被证实可以用来制备OSCs或OSMs，这些技术主要包括半月板刮涂、狭缝挤出印刷、凹版印刷、丝网印刷、喷墨打印等。总之，通过结合以上两点可以成功制备出低效率损失和高重现性的大面积柔性OSCs，这将有利于未来OSCs或OSMs的工业化制备和商业化发展。

2 高性能大面积OSCs的印刷制备思路

目前，具有优异光电性能的OSCs制备方式通常是采用旋涂技术，这可确保光敏层形成纳米级的互穿网络结构，同时在最佳效率条件下，光敏层的膜厚仅为110 nm左右，这些限制了柔性大面积OSCs的商业应用。首先，光敏层形貌和相分离结构的一致性会严重影响因等比例放大器件面积而导致的OSCs性能下降。然而，由于每种涂布/印刷方法都有其既定的操作模式，因此很难控制大面积BHJ薄膜的形貌和相分离结构一致性。其次，目前高效给体/受体光敏层的综合性能与膜厚有关，而商业化的R2R印刷技术还无法制备高精度的大面积纳米级薄膜，这意味着其制备再现性较差。最后，结合上述关键问题，光敏层可能存在大量的点缺陷，这在粗糙度相对较高的柔性衬底（如银纳米线、银网或ITO/PET透明电极等）上会加剧形貌劣化，从而导致器件效率不理想，因此，设计具有显著成膜性能、厚度不敏感性的给体/受体材料以及探索旋涂工艺与R2R印刷技术之间的定量转换关系，能帮助实现制备高质量的柔性大面积OSCs或OSMs[149-151]。

以前的文献中，人们为印刷制备高性能OSCs做了大量工作，包括调整光敏层结构和合成对厚度不敏感的给体/受体材料。相分离结构、相纯度和给体/受体聚集程度组成的形貌决定了薄膜的质量，可通过多种处理方法对其进行优化，例如三元共混设计、热退火或溶剂–蒸汽处理等。上述优化过程对于保持形貌一致性以实现大面积R2R印刷的高效厚膜器件具有重要意义[6-12,152-158]。除了形貌控制外，合成具有高载流子迁移率和低复合特性的新型给体/受体材料也适用于厚度不敏感性器件的制备[151]。其中一个有效的思路是将分子链做成face-on堆砌的分子排列结构，这可以进一步促进载流子的梯度传输。在本节中，重点讨论了大面积OSCs光敏层的形貌一致性控制，并简要总结新型厚度不敏感性光敏层材料的设计[159]。通常，从旋涂OSCs到具有大面积光活性区域的印刷器件，可以观察到明显的效率损失，这已通过大量研究工作得到验证。造成这种现象的原因很复杂，例如：玻璃衬底和柔性衬底的形貌差异，针对大面积制备的不同印刷方法的适应性，以及随着器件尺寸的增加而导致成膜均匀性的变化等[159]。总之，主要原因在于不同器件面积、不同印刷方法制备的OSCs光敏层形貌一致性难以保证。形貌一致性包括2个方面，即内部相分离结构和活性层的薄膜厚度。

3 大面积制备的印刷技术及器件结构设计

随着刚性OSCs的PCE大幅提高至19%以上，大面积柔性OSCs和有机太阳电池组件（OSMs）已经引起了研究人员的广泛兴趣和研究报道[12]。一般来说，旋涂工艺是制备OSCs的主要应用技术，但旋涂工艺并不适合OSCs的大批量生产。因为随着旋涂制备OSCs有效面积的增大，活性层形貌和相分离会发生一些无意和非理想的退化，这些都会影响器件的整体性能。因此，针对高效刚性和柔性OSCs的大面积R2R印刷技术逐渐发展起来[4,5,13,15-17]。

考虑到生产效率和实际应用，低温印刷柔性OSCs的研究意义远高于刚性器件，这也是OSCs相对于无机太阳电池的优势所在。为了实现柔性OSCs的商业化生产，各种R2R打印方法已被广泛探索和报道。然而，目前还没有标准且优秀的印刷技术来制备高效的大面积光电器件，因此开发合适的R2R印刷方法也是一个紧迫的挑战[4-5,15]。根据印刷油墨是否与柔性衬底接触，通常印刷/涂布技术可分为接触式和非接触式（图2）[149-154,159-160]。其中刮涂、狭缝挤出印刷、凹版印刷、喷墨打印、丝网印刷、喷涂、平板刮涂、柔版印刷都是制备OSCs的有效印刷方法。Viana等[161]提出了印刷参数与薄膜质量之间的联系，将其应用在柔性塑料衬底（PET、PEN、PI等）上制造印刷电子设备，并介绍了薄膜质量总是与表面润湿性、粘附性和延展性有关。对于柔性塑料衬底来说，印刷薄膜的均匀性和成膜质量较差是由于表面能量低，这个问题可以通过在印刷前进行额外表面处理（UVO或PLASMA处理）来解决。因此，在感光层从湿润状态转变为固态薄膜的过程中，控制早期材料聚集和相分离行为对其形貌演变非常重要。然而，选择一个特定的印刷参数来确定不同印刷/涂布方法之间的内在关系是不切实际的。Chen等[15]报道了通过计算冲量积累并采用旋涂工艺和狭缝挤出印刷方法制备富勒烯和非富勒烯受体体系OSCs光敏层形貌演变机制的研究工作。通过形貌、分子构象测试以及粗粒化分子动力学模拟，他们发现了基于剪切冲量累积量的不同沉积方式下光敏层形貌和相分离之间的明显关系。他们进一步研究了不同印刷方式下的光敏层形貌一致性，验证了旋涂和狭缝挤出印刷之间剪切冲量的定量转换系数，发现该系数可适用于各种OSCs体系。

3.1 半月板刮涂

半月板刮涂是制备高效OSCs的有效方法，可初步替代旋涂技术（图3）[13-16,83,92]。半月板涂覆工艺是利用半月板的水平位移将油墨涂覆在刚性或柔性衬底上，从而得到纳米或微米厚度的薄膜。有机薄膜的印刷质量可以通过控制半月板与印刷衬底的距离、衬底的表面能和半月板的位移率来实现。其中，半月板与印刷衬底的距离对薄膜厚度有直观的影响，半月板液面的连续存在也可以保证印刷过程的顺利进行。衬底的表面能会调节衬底材料上油墨的润湿性，这不仅对薄膜厚度有影响，而且对薄膜质量有巨大影响。半月板涂布速度（）对薄膜厚度（）的影响是复杂的，它们之间的主要关系遵循两种模型。第一个是蒸发模型，它要求半月板涂层速度小于4 mm/s，log()与log()的斜率约为−0.97。在该模型中，半月板离开油墨表面后，印刷油墨会迅速变干，半月板与衬底之间的溶剂蒸发决定了光敏层溶液的沉积质量。当半月板刮涂速度大于20 mm/s时，涂布过程遵循Landau‒Levich模型。在这种模式下，log()与log()的斜率约为0.65，由于半月板刮涂速度非常快，印刷油墨并未完全变干（图3d）。因此，需要一个额外的处理来确保薄膜质量[162]。除了设备参数需要调整外，油墨的表面张力、黏度等流变性能对最终成膜质量也有明显影响。干燥后的薄膜最终厚度可以通过下式计算。

图2 OSCs当前主流的印刷制备方法

(1)

式中：为薄膜厚度；为半月板与衬底之间的距离；为印刷油墨的浓度；为干燥薄膜的密度。

2008年，Mens等[163]首次报道了采用MDMO– PPV:PC61BM体系的光敏层通过半月板刮涂工艺制备OSCs。在相同的油墨条件下，半月板涂层薄膜中的PC61BM显示出比旋涂薄膜中更高的结晶度，这与固态核磁共振表征结果相一致。这一结果表明，由于溶剂的快速蒸发过程，与半月板涂层薄膜相比，旋涂薄膜可能不完全适用于热力学平衡规律。利用这一特殊现象，Ma等[83]通过半月板刮涂制备OSCs，证实光敏层内给体和受体材料的平衡结晶性。结合三元共混策略，基于PBDB–T：PTB7–Th：FOIC的光电器件PCE值达到12.02%。2018年，Hou等[43]通过半月板涂覆工艺，用环保溶剂（四氢呋喃/异丙醇和邻二甲苯/1–苯基萘）制备了高效的OSCs，基于PBTA–TF:IT–M体系可以获得11.7%的优异PCE。同时，当器件尺寸增加到1 cm2时，基于半月板刮涂的THF/IPA主溶剂的OSCs获得了10.6%的PCE。此外，他们通过共聚聚合物合成了一种效率超过15%的给体材料。因为该共聚物最优化的溶解度，基于环境友好型溶液（THF）的半月板刮涂的光电器件达到了令人印象深刻的13.1%的PCE。他们还为OSCs设计了阴极缓冲层材料（NDI–N和NDI–Br），采用NDI–N作为缓冲层，用半月板刮涂工艺制备的1 cm2大面积OSCs器件实现了13.2%的PCE[92]。最近，Min等[13]报道了几项关于通过半月板刮涂工艺制备的具有双层结构的平面异质结高效OSCs的研究工作。他们提出，由于复杂的形貌控制规律，本体异质结结构不适合大面积的OSCs批量制备。相比之下，双层结构具有许多独特的特点，包括可控的“p-i-n”形态、良好的电荷传输和提取性能以及良好的普适性。结合半月板刮涂工艺，基于PM6∶Y6系统的逐层OSCs的最佳PCE达到16.35%。更重要的是，他们制备了11.52 cm2的OSMs，其几何填充因子约为90%，最佳PCE值为11.86%（图3a）。最近，Li等[148]报告了通过非卤化溶剂连续沉积的分级体异质结策略来制造高质量的OSCs。通过这种方式，空气环境中半月板刮涂的OSCs实现了16.77%的高PCE。

a 基于逐层（LbL）的大面积太阳组件的工艺流程 b 有效面积为11.52 cm2的太阳组件图像[13] c 带DIO的BHJ、无DIO的G-BHJ和带DIO时G-BHJ在整个薄膜中聚合物重量含量的变化[148] d 使用叶片涂层NDI-N作为缓冲层的器件J-V和外部量子效率（EQE）曲线[92] e 薄膜厚度与半月板刮涂速度的关系 f 墨滴在疏水衬底上干燥时收缩和表面活性剂钉扎效应[162]

与旋涂器件相比，除了OSCs相对乐观的效率外，半月板刮涂还有一个最突出的优势，那就是节省原材料。一般来说，旋涂OSCs需要40～55 μL的光敏层溶液来满足器件的制备，而半月板涂层只需要7～9 μL。对于未来商业化生产的OSCs来说，降低材料损耗是非常重要的。值得注意的是，半月板刮涂中的溶剂蒸发率也远低于旋涂处理中的溶剂蒸发率。这种缓慢的成膜过程可能会导致光敏层中给体和受体过度聚集或结晶[164]。因此，调节并合理适当利用这一现象很有必要（图3d）。

3.2 狭缝挤出印刷

狭缝挤出印刷也是一种印刷高效大面积OSCs的有效方法，它被认为是有机光电器件R2R生产最具前景的方法（图4）[165-171]。通过精密控制，狭缝挤出设备可连续印刷多层图纹的刚性或柔性OSCs，这就减少了多次刻蚀过程，简化了制备步骤，因此非常适合大面积OSCs的生产。在印刷过程中，油墨通过压力槽或输液泵被挤入槽头，在此进行图案化和预成型阶段。因此，适当控制进料速度、槽间距、图案精度和印刷定位精度非常重要。与半月板刮涂工艺类似，狭缝挤出印刷也需要注意模头与衬底之间的距离以及模头或衬底的移动速度。只要上述参数能被严格控制，狭缝挤出印刷将是一项具有高度自动化的优秀技术。狭缝挤出印刷工艺的原理图和实物照片如图4a所示，模头是槽模设备中最重要的部件，它需要具备耐腐蚀、抗氧化、精度高等特点。膜厚控制也是值得进一步探讨的问题，它会在模头中受到印刷油墨预成膜的影响。预成膜与槽距（0.2～100 mm）和油墨黏度（1～20 Pa·s）有关，因此油墨流变性与设备参数的协调控制成为生产高质量薄膜的关键[4,62,165]。同时，狭缝挤出印刷为薄膜提供了一个缓慢的干燥过程，对其内部结构的形态和相分离调节处理是必不可免的。狭缝挤出印刷制备的干膜厚度可由下式计算。

(2)

式中：为干膜厚度；为进料速度；为胶带速度；为衬底宽度；为印刷油墨中的固体含量；为干膜密度。

2011年，Zimmermann等[167]通过狭缝挤出印刷技术制备了基于P3HT：PCBM系统的柔性OSCs，其PCE为0.64%。后来，Tan等[166]结合狭缝挤出印刷技术，在PV2000和PCBM系统上实现了全溶液和环境可加工有机光伏组件的PCE为7.56%。2017年，Bao等[85]证明了一种光敏层设计，该光敏层包括大面积、利用给体和受体之间具有合适的相分离结构的溶液处理的全聚合物OSCs。通过使用不同结晶度的光敏层材料（给体和受体），他们验证了给体和受体的微相分离域的尺寸与共轭聚合物的结晶度成反比。由于这一特殊现象，通过狭缝挤出印刷工艺制备了大面积（10 cm2）的全聚合物OSCs，并实现了5%的PCE。Russell等[168]报道了一种高效的狭缝挤出印刷全聚合物OSCs，其活性层为PTzBI∶N2200系统，PCE高达9.1%，这是狭缝挤出印刷全聚合物OSCs的最佳效率。此外，Vak等[169]开发了一种用于OSCs的温控狭缝挤出印刷技术，并研究了衬底和溶液温度对器件性能、薄膜形态、分子结构和载流子输运的影响。当使用温度为120 ℃和90 ℃的热衬底和溶液，他们制备了刚性和柔性OSCs，PCE分别为10.0%和7.0%。2019年，Min等[170]使用PBDB-T-SF∶IT-4F体系作为狭缝挤出印刷的OSCs的光敏层，并在刚性衬底上实现了12.9%的PCE，与旋涂或半月板刮涂工艺相比，其PCE更高。同时，通过狭缝挤出印刷技术制造的基于柔性衬底的OSCs和OSMs效率分别达到12%和9%以上，这表明该大面积生产技术的可行性。最近，为了探索在不同模具温度和衬底温度下的聚集和结晶演化，Ma等[171]在狭缝挤出印刷过程中对PM7∶IT4F系统进行了原位测量。由于改善了激子解离、电荷传输和抑制了非辐射电荷重组，在60 ℃模具温度和60 ℃衬底温度下，OSCs获得13.2%的PCE值。

虽然狭缝挤出印刷可能是最适合OSCs商业化生产的印刷技术，但在实际应用过程中仍有许多问题有待解决。首先是制备重现性性，目前对于高质量薄膜的大规模生产，狭缝挤出印刷仍有困难，大部分的研究报告显示，可通过在印刷薄膜上选择高质量的区域来制备光电器件，但连续且一致的高效制备技术还没有实现。因此，加深对薄膜形貌和相分离调控的理解是必要的，这对柔性OSCs的商业化发展至关重要。其次是对新的制备技术的探索，在以前的报道中，一些成熟的技术如热印刷和闪蒸干燥以及新颖的器件结构如双层印刷工艺是非常实用的，因此，应该尝试更多优秀的方法来制备基于狭缝挤出印刷工艺的OSCs，这对于发展完美的狭缝挤出印刷技术也是非常重要的。

3.3 模组化OSCs的R2R印刷技术

R2R印刷技术一种特殊的印刷技术，已广泛应用于工业用品、塑料、玻璃、金属片、陶瓷片、电子板等的制备。印刷油墨的高效率和高质量成膜特性使R2R印刷能够连续制备有机薄膜。一般来说，一个完整的R2R印刷技术由多个部件组成，包括放卷区、放卷区、表面处理区、印模区、纠偏区、超声波清洗区、退火区、电晕区、风淋区、防静电区等。在印刷过程中，柔性塑料衬底被支撑在R2R放卷区和收卷区并做协调运动，从而实现塑料衬底的定向运动。在具体的制备过程中，首先是塑料衬底的清洗过程，一般采用醇类溶剂（乙醇、异丙醇等）多次超声波处理，并低温退火处理。然后，印刷模头（通常是槽模头）以设定的速度在衬底上涂抹油墨。为保证印刷质量，在R2R印刷中加入电晕处理工艺，这将提高衬底的表面能，从而优化油墨的渗透。结合与油墨成膜条件相匹配的退火工艺，可以得到具有条形图案的干膜。对于OSCs的模组化条状定位设计，衬底的定位偏差可以通过纠偏区域实现，因此，合理改进R2R印刷技术实际上可以完成除金属背电极以外的所有OSCs结构的制备，从而实现完整的印刷器件流程。由于低温溶液制备的技术特点，OSCs的印刷工艺与R2R印刷技术完美兼容（图5），对此的进一步研究也是实现有机器件商业化的关键。

a 模块制备的总体程序 [167] b 具有独立控制参数的槽模涂层的概念图 c 槽模涂层装备的照片和实现的带有ZnO层的高质量BHJ薄膜 [170] d 热槽模具涂层示意图 e R2R热槽模具涂层的实验装备 f 槽模涂层OSCs的J–V特性[169] g 用于监测成膜过程中形态演变的原位印刷技术示意图[171]

Krebs等[62]早期就对R2R印刷制备OSCs作出了代表性的研究工作。他们通过狭缝挤出印刷在ITO/PET衬底上沉积ZnO、P3HT∶PCBM和PEDOT∶PSS油墨，然后通过丝网印刷覆盖顶部金属银电极。通过这种方法，他们制备了一个全印刷的倒置OSCs（具体配置为PET/ITO/ZnO/P3HT∶PCBM/PEDOT∶PSS/Ag），其性能可与实验室小面积旋转涂器件的PCE相媲美。此外，全印刷器件在潮湿的环境中表现出优异的稳定性，这优于普通器件，但它很容易被氧气影响。与旋涂器件类似，R2R印刷技术中也存在各种优化思路和薄膜改善方案。在印刷参数方面，可以通过调整卷绕张力、基材移动速度、送墨速度、模头与衬底间距、槽模头间距等来实现均匀成膜和厚度控制。此外，也可以应用一些常见的后处理工艺，如溶剂退火、溶剂添加剂、给体/受体配置、溶剂退火和纳米级相分离调节等，其处理效果比旋涂技术更显著。与旋涂工艺相比，R2R印刷参数的控制比旋涂速度和加速度的确定更简单，材料损耗也少很多。既能降低生产成本，又能减少环境污染，这对商业转型至关重要。更重要的是，R2R印刷技术提供了更具体、更精确的变量控制，这对于印刷工艺的标准化很重要，这也是旋涂工艺的最大劣势。例如，对于旋涂工艺，为了获得准确的给体/受体比例，需要10多种不同的给体/受体比例，这需要消耗大约100 mg的聚合物材料和60 min。相比之下，对于R2R印刷，至少需要200种不同的给体/受体比例，但仅需要使用60 mg聚合物材料和35 s。这充分展示了R2R印刷技术的先进性[174]。

狭缝挤出印刷和半月板刮涂在OSCs的光电性能方面也存在明显的缺陷，特别是FF损耗。印刷有机器件的测试结果通常呈现“S”型曲线，这与正常器件的“J”型曲线不同。这种现象可能是由于光敏层或界面处的能级势垒引起的载流子传输或提取的损失造成的。光浸泡处理可以缓解这一问题，它可以逐渐将“S”形曲线转变为“J”形曲线，从而实现FF的恢复。不幸的是，这种FF损失会在几天后再次出现，需要进一步重复光浸泡处理[175]。这一动态降解过程可能与光电导率的变化、ZnO电子传输层中杂质的降解或封装器件中残留氧气的影响有关。光浸泡处理通常会带来大量的能量损失，增加生产成本，并使有机器件的生产过程复杂化。同时，这不适合大面积OSCs的连续制备，因此需要开发或寻找新技术来解决这一缺陷，这也是R2R印刷有机器件商业化生产的最大障碍。总的来说，虽然R2R印刷有明显的缺陷，但它仍然是实现OSCs商业化生产的最佳技术。特别是柔性器件，下一阶段将围绕有机器件中这一技术的研究和设备开发。

a 用PDTTDABT生产R2R的照片以及成品模块的叠层和在太阳模拟器下测试单个模块的照片[172] b R2R印刷设备的照片[15] c OSCs模块及其作为LED条纹和儿童夹克保暖口袋的能源供给者[173] d R2R涂层的PET–ITO卷轴和样品条[173]

Krebs等[176]定义了大面积印刷OSCs的完整制备工艺，旨在实现有机器件从实验室的小面积制备到工业界的大面积生产转移。但在生产成本方面，他们的研究没有考虑到人工成本、材料消耗以及相关的水电费用。报告的主要研究内容是通过印刷一种新型的透明电极来取代ITO电极，这样可避免OSCs每,层的图案化过程。基于这种通过R2R印刷技术实现的无ITO透明电极设计，结合含铜的Kapton箔和钛金属背电极，全印刷的有机器件得到0.061%的低PCE，sc为42.57 mA，oc为0.178 V和填充因子（FF）为25%。虽然这种方法为有机器件的印刷制备提供了指导和参数规范，但由于光电转换效率低，不值得进一步研究。Bundgaard等[172]展示了通过空气中的全溶液处理和狭缝挤出印刷技术，结合印刷的金属网格背电极制备的半透明柔性OSCs。这进一步扩大了印刷技术在连续大面积制造OSCs中的应用潜力。Wei等[177]在ITO/PET衬底上沉积了电子传输层和光敏层，制备了2节或4节串联的OSCs和OSMs。对于单结电池、双结串联电池和四结串联电池，有机器件的光电效率分别达到5.75%、5.82%和5.18%。在校准后的太阳模拟器下照射强度为100 mW/cm2的AM 1.5G照明下，四节串联OSCs可正常工作。这些结果初步证明，目前商业化的R2R印刷技术可以实现全印刷OSCs的制备，这是其他印刷技术所不具备的优势，因此，进一步的印刷探索和设备升级应该是首要任务。Chen等[15]报道了一种将狭缝挤出R2R印刷设备制备的柔性有机光伏器件升级到模块规模（15 cm2）而没有明显效率损失的一般方法。首先应用涂布/印刷过程中的剪切冲力来调整富勒烯和非富勒烯受体系统的BHJ活性层的形态演变，并得到狭缝挤出印刷和旋涂之间剪切冲量的定量转换系数。基于1.04 cm2通过狭缝挤出印刷的柔性OSCs的PCE在PTB7-Th∶PC71BM和PBDB-T∶ITIC系统中达到9.10%和9.77%。对于15 cm2的柔性模块，其有效效率也达到了7.58%和8.90%，并具备令人满意的机械力学稳定性和制备重现性。

4 结语

随着科技的飞速发展，可穿戴电子设备逐渐在生活中发挥着越来越重要的作用，因此，柔性连续电源器件作为其核心部件之一，其研究具有科学和实际应用意义，可应用于电动汽车、便携式电子设备和物联网领域。具有优良光电转换性能和环境稳定性的大面积OSCs有望适应未来民用光伏器件的实际应用，特别是柔性OSCs在可穿戴电子领域具有巨大潜力。遗憾的是，尽管在刚性和柔性衬底上，单结OSCs的最大PCE已经超过19%和16%，但现有的制备技术（旋涂等）、功能层材料和器件配置都不适合大面积OSMs的工业制备，因此，即使在选择性能最好的给体/受体材料体系时，印刷技术的合理选择、大面积印刷工艺的巨大性能损失仍然是限制OSCs商业化的瓶颈。

在此，文中总结了柔性OSCs各功能材料的可行性选择，各种印刷技术的优势和挑战，以及OSMs性能的优化思路。文中旨在为读者提供与先进的印刷制备OSCs相关的全面见解和最新进展，通过分析现阶段的技术瓶颈和大面化制备OSCs过程中的效率损失，以获得高性能、可印刷的大面积光伏组件。希望通过这篇综述，为推动下一代柔性光伏清洁能源的商业化提供一站式参考，并突出低温溶液法印刷有机光伏组件的技术优势。同时也相信，只要合理设计光伏材料、设计合理的模组化OSCs结构和合适的印刷技术选择，就能实现低效率损失的柔性有机光伏器件的连续印刷制备，未来有机太阳电池的商业化制造也将近在咫尺。

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Large-area Flexible Organic Solar Cells: Modular Design and Printing Technologies

SHI Lin-feng1, YUAN Hao1, MENG Xiang-chuan1,2, HU Xiao-tian1,2, CHEN Yi-wang1,2,3

(1. Peking University Yangtze Delta Institute of Optoelectronics, Jiangsu Nantong 226010, China; 2. College of Chemistry/Institute of Polymers and Energy Chemistry (IPEC), Nanchang University, Nanchang 330031, China; 3. Institute of Advanced Scientific Research (iASR)/Key Lab of Fluorine and Silicon for Energy Materials and Chemistry of Ministry of Education, Jiangxi Normal University, Nanchang 330022, China)

The work aims to provide investigators with comprehensive insights and recent advances related to OSCs manufacturing technology, analyze existing technical bottlenecks and unsolved scale efficiency losses to obtain scalable and printable large-area photovoltaic modules. This review introduced the selection of functional layer materials, the current status of printing process research and large-scale efficiency loss, and focused on the technical challenges in printing and preparation of flexible and high-efficiency large-area organic photovoltaic devices. This will promote the integrated application of printable organic semiconductor materials in next-generation clean energy, and attract widespread attention in application to wearable electronics, building-integrated photovoltaics, the Internet of Things, etc.

organic photovoltaic, modular design, flexible device, printing technology

TS801.4

A

1001-3563(2022)19-0011-16

10.19554/j.cnki.1001-3563.2022.19.002

2022–07–12

国家自然科学基金（51833004，22005131，52173169，52222312）

施淋枫（1991—），女，中级，主要研究方向为印刷光电器件。

胡笑添（1990—），男，博士，研究员，主要研究方向为印刷光电器件。

责任编辑：曾钰婵