综述:大面积钙钛矿太阳能电池研究进展

通过组分、钙钛矿薄膜生长控制和钙钛矿/传输层界面工程的方式,钙钛矿太阳能电池的光电转换效率在10余年间已超过25%。但是,目前高性能钙钛矿太阳能电池均是基于小面积制备(一般小于0.1 cm2)。从商业应用的角度来说,制备大面积器件是钙钛矿太阳能电池商业化发展的必要途径。

近期,中国科学院半导体研究所游经碧研究员领导的团队对大面积钙钛矿太阳能电池的研究进展进行了综述(图1)。重点总结了在制备高性能大面积钙钛矿太阳电池方面的关键技术,即通过优化大面积器件的制备方法、生长高质量的钙钛矿薄膜以及选择适当的电荷传输层以获得高性能器件,其有助于大面积钙钛矿太阳能电池的商业化发展。该综述发表在Photonics Research 2020年第7期上(Yang Zhao, Fei Ma, Feng Gao, Zhigang Yin, Xingwang Zhang, Jingbi You. Research progress in large-area perovskite solar cells [J]. Photonics Research, 2020, 8(7): 070000A1),并被选为Perovskite Photonics专题封面文章。

图1. 文章内容总结

目前,高效小面积钙钛矿太阳能电池一般利用旋涂法制备,大面积钙钛矿太阳能电池的光电转换效率与之相比仍存在差距。此外,利用旋涂法很难得到高质量的钙钛矿薄膜(面积>1 cm2)。因此,要制备高效大面积钙钛矿太阳能电池,制备方法、钙钛矿以及载流子传输层的制备条件都需要做进一步改进。

大面积钙钛矿太阳能电池制备方法

为得到均匀且高质量的钙钛矿薄膜,大面积薄膜制备方法被应用到钙钛矿太阳能电池制备中,例如刮涂法、狭缝法、喷涂法、喷墨印刷和卷对卷法等(图2)。通过对大面积制备方法细节的优化来提高大面积钙钛矿太阳能电池的性能,例如衬底加热以及n2流辅助成膜等。

图2. 大面积钙钛矿太阳能电池制备方法。图a-f分别是旋涂法、刮涂法、狭缝法、喷涂法、喷墨印刷和卷对卷法.

高质量钙钛矿薄膜生长

制备高效小面积钙钛矿太阳能电池的方法也可以应用到大面积器件制备中。钙钛矿吸光层决定整个器件的性能,通过对钙钛矿前驱体溶液的调控可以制备高质量钙钛矿薄膜,进而提升大面积钙钛矿太阳能电池的性能。例如通过对溶解钙钛矿溶剂的优化、组成钙钛矿组分的调控以及添加剂的辅助成膜等方式来制备均匀且高质量钙钛矿吸光层(图3)。

图3. 调控钙钛矿前驱体制备高质量钙钛矿薄膜. (a, b)溶剂;c 组分;d添加剂。

载流子传输层制备

载流子传输层在钙钛矿太阳能电池中的作用是对载流子进行抽取和输运。在大面积钙钛矿太阳能电池中,需要选择合适的载流子传输层。

目前已有众多关于载流子传输层优化的研究报道(图4)。 以Spiro-OMeTAD为例,它是高效钙钛矿太阳能电池的首选,但是由于其较快的结晶性导致其在大面积器件制备应用中器件性能衰减。Cheng等通过对Spiro-OMeTAD的改性,利用 Bifluo-OMeTAD作为器件的空穴传输层,抑制了空穴传输层在Slot-die工艺印刷过程中的快速结晶,进而提升了利用器件的性能。该工作为选择合适的载流子传输层提供了新的思路。

图4. (a、b)器件结构和器件J-V曲线; (c、d) Bifluo-OMeTAD和Spiro-OMeTAD结构以及器件的J-V曲线;(e、f) 使用P3HT作为HTL的器件结构和I-V曲线; (g、h) GO和Cl-GO的DFT模拟以及不同薄膜的PL光谱和TRPL光谱。

总结和展望

大面积钙钛矿太阳能电池效率远落后于小面积钙钛矿太阳能电池,通过对制备方法优化、组分调控以及载流子传输层优化选择的方式可以得到高性能大面积钙钛矿太阳能电池。

和传统太阳能电池相比,钙钛矿太阳能电池稳定性较差,对于大面积太阳能电池其稳定性也需进一步提升。

Research progress in large-area perovskite solar cells

The record power conversion efficiency of perovskite solar cells (PSCs) has impressively exceeded 25% in 10 years due to composition engineering, perovskite film growth control and perovskite/transport layer interface modification. However, the high efficiency PSCs are usually small-area (<0.1 cm2). For commercial application, the preparation of large-area devices is the necessary step for the development of PSCs.

At present, a series of research progress in large-area PSCs was summarized by the research team led by Prof. Jingbi You from Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China This paper summarizes the key technologies in the preparation of high-performance large-area PSCs. By optimizing the preparation method of large-area modules, growing high-quality perovskite films, reducing carrier recombination centers, and selecting appropriate charge transport layer to obtain high-performance devices, which will help the commercial development of large-area PSCs (Fig. 1). It was published in Photonics Research, Vol. 8, Issue 7, 2020 (Yang Zhao, Fei Ma, Feng Gao, Zhigang Yin, Xingwang Zhang, Jingbi You. Research progress in large-area perovskite solar cells[J]. Photonics Research, 2020, 8(7): 070000A1)and was chose as On the Cover of Special Issue on Perovskite Photonics.

Fig. 1. Summary of the article content

At present, high-efficiency small-area PSCs are generally prepared by spin-coating. There is still a gap in the photoelectric conversion efficiency (PCE) between small-area PSCs and large-area PSCs. It is difficult to obtain high-quality perovskite films by spin-coating (>1 cm2). In order to prepare a high-efficiency large-area PSCs, the preparation method,the preparation conditions of the perovskite and carrier transport layer need to be further improved.

1. Deposition Methods of Large-area PSCs

In order to obtain a uniform and high-quality perovskite film, large-area film preparation methods, such as Blade coating, Slot-Die coating, Spray coating, Inkjet printing and Roll-to-Roll, are applied to the preparation of PSCs (Fig. 2).

The performance of the large-area PSCs could be further improved by optimizing the preparation details of the large-area preparation methods, for example, substrate heating and n2 flow assisted film formation.

Fig. 2. Deposition methods of large-area PSCs. a-f are Spin-coating, Blade coating, Slot-Die Coating, Spray Coating, Inkjet Printing and Roll to Roll, respectively.

2. Growth of High-quality Large-area PSCs

The method for preparing high-efficiency small-area PSCs can also be applied to the preparation of large-area devices. The perovskite light-absorbing layer determines the performance of the devices, and high-quality perovskite films can be prepared by adjusting the perovskite precursor solution, thereby improving the performance of large-area PSCs. For example, through the optimization of the solvent for dissolving the perovskite, the adjustment of the composition of the perovskite components, and the auxiliary film formation of additives, a uniform and high-quality perovskite light-absorbing layer can be prepared (Fig. 3).

Fig. 3. Different methods of preparing highly perovskite films, a-d are the Solvent engineering, Composition engineering and additives engineering, respectively.

3. Fabrication of Large-area Charge Transport Layers

The carrier transport layer plays a role in the extraction and transport of carriers in the PSCs. In large-area PSCs, a suitable carrier transport layer needs to be selected.

In many research reports, the carrier transport layer has been optimized (Fig. 4). Taking Spiro-OMeTAD as an example, Spiro-OMeTAD is the first choice for high-efficiency PSCs, but the performance of its devices in the preparation of large-area devices is affected due to its faster crystallinity. Cheng et al. modified Spiro-OMeTAD and used Bifluo-OMeTAD as the hole transport layer of the device, which suppressed the rapid crystallization of the hole transport layer during the slot-die printing process, thereby improving the performance of the device. This work provides a new idea for the selection of the appropriate carrier transport layer.

Fig. 4. (a, b) Structure and J-V curve of the device with the doped charge carrier extraction layers. (c, d) Comparison of the Bifluo-OMeTAD and Spiro-OMeTAD and J-V curve of devices. (e, f) Device structure and I-V curve of using P3HT as the HTL. (g, h) The DFT simulation of GO and Cl-GO and PL spectra and TRPL spectra for different films.

4. Outlook and summary

(1) The efficiency of large-area PSCs is far behind that of small-area PSCs. By optimizing the preparation method, adjusting the composition, and optimizing the selection of the carrier transport layer, high-performance large-area PSCs can be obtained.

(2) Compared with traditional solar cells, the stability of PSCs is poor, and the stability of large-area PSCs needs to be further improved.