Large-Area Polymer Solar Cells with High thermal stability and Performance

Xiaoniu Yang1*, Xiaoli Zhao1, Tong Zhang1, Zelin Li1,2, Dalei Yang1,2 and Zidong Li1,2

1State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Str. 5625, Changchun 130022, P. R. China
2University of Chinese Academy of Sciences, Beijing 100049, P.R. China

Polymer solar cells (PSCs) have attracted more and more attentions, due to the features of light-weight, flexibility, low cost and the power conversion efficiency (PCE) has been boosted up to be over 13%.[1] Nevertheless, the long-term stability of PSCs still remains to be a great challenge for fullerene and non-fullerene PSCs. We systemically investigated the relationship between the molecular structure and thermal stability in fullerene system. The results showed that with the increase of conjugated side chain length, the polymer bearing thieno[3,2-b]thiophene as side chains (P3) showed outstanding thermal stability and could preserve 90% of their initial efficiencies after thermal annealing at 100 ℃ for one month.[2] After finely modifying the molecular structure of P3,[3] the resulted polymer PBTIBDTT afforded an enhanced efficiency of over 9.4% with an active layer thickness over 200 nm and high thermal stability, which fulfills the prerequisite of solution printing technology and practical application. More interesting, when this polymer was paired with the typical non-fullerene small acceptor (ITIC-F), the device without any additive or post-treatment delivered an efficiency over 11% with active layer thickness over 200 nm, which indicates the potential application of non-fullerene PSCs in future mass production technology. By optimizing the ink formulations and spray-coating parameters, large area PSC modules with active layer over >38.5 cm2 were achieved and the efficiency could retain ca. 80% of the corresponding small area device made by spin-coating method. Furthermore, “Layer-Filter Threshold” technique for near-infrared laser was developed to realize over 90% of geometric fill factor for the first time, which was beneficial for further improving the efficiency of PSC module.[4]

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[2] Z. D. Li, W. Fan, H. Y. Lv, D. L. Yang, Z. B. Chen, X. L. Zhao,  X. N. Yang,  Adv. Mater. 27, 6999 (2015)
[3] Z. L. Li, D. L. Yang, X. L. Zhao, T. Zhang, J. D. Zhang, X. N. Yang,  Adv. Funct. Mater. 28, 1705257 (2018)
[4] F. Ye, Z. B. Chen, X. L. Zhao, J. Y. Chen, X. N. Yang,  Adv. Funct. Mater. 25, 4453 (2015)