Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener Design of novel thiazolothiazole-containing conjugated polymers for organic solar cells and modules Alexander V. Akkuratov a, ⁎ , Sergey L. Nikitenko a , Andrey S. Kozlov a , Petr M. Kuznetsov a , Ilya V. Martynov a , Nikita V. Tukachev a , Andriy Zhugayevych b , Iris Visoly-Fisher c,d , Eugene A. Katz c,d , Pavel A. Troshin a,b a Institute for Problems of Chemical Physics of the Russian Academy of Sciences (IPCP RAS), Academician Semenov avenue 1, Chernogolovka, Moscow Region 142432, Russian Federation b Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld.1, Moscow 121205, Russian Federation c Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion 8499000, Israel d Ilse Katz Institute for Nanoscale Science & Technology, Ben-Gurion University of the Negev, Be’er Sheva 8410501, Israel ARTICLE INFO Keywords: Thiazolothiazole Conjugated polymers Organic solar cells Photovoltaic modules Slot-die coating ABSTRACT One of the major challenges in the field of organic photovoltaics is associated with high-throughput manu- facturing of efficient and stable organic solar cells. Practical realization of technologies for production of large- area organic solar cells requires the development of novel materials with a defined combination of properties ensuring sufficient reliability and scalability of the process in addition to good efficiency and operation stability of the devices. In this work, we designed two novel polymers comprising thiazolothiazole units and investigated their performance as absorber materials for organic solar cells and modules. Optimized small-area solar cells based on P1/[70]PCBM ([6,6]-phenyl-C 71 -butyric acid methyl ester) blends exhibited promising power con- version efficiency (PCE) of 7.5%, while larger area modules fabricated using slot die coating showed encouraging PCE of 4.2%. Additionally, the fabricated devices showed promising outdoor stability maintaining 60–70% of the initial efficiency after 20 sun days being exposed to natural sunlight at the Negev desert. The obtained results feature the designed polymer P1 as a promising absorber material for a large-scale production of organic solar cells under ambient conditions. 1. Introduction Organic solar cells (OSCs) are recognized as a promising renewable energy technology (Dong et al., 2019; Wang et al., 2018; Fan et al., 2019). Advanced properties of OSCs such as light weight, flexibility, low cost, and solution processability have attracted a considerable at- tention from academia and industry. Particularly, OSCs can be used as promising energy sources for low-power indoor electronic devices (You et al., 2019). State-of-the-art OSCs demonstrate commercially compe- titive power conversion efficiencies (PCEs) of > 17% (Meng et al., 2018). However, this superior performance was achieved for small-area devices (0.05–0.1 cm 2 ) while using laboratory spin-coating technique. Unfortunately, the performance of organic solar cells drops dramati- cally when going to larger-area devices fabricated using roll-to-roll compatible coating and printing techniques such as slot-die coating, doctor blading, inkjet printing, screen printing, etc. (Gu et al., 2017; Krebs, 2009). Severe efficiency roll-offs are mainly attributed to the unsuitable film formation properties, poor charge mobilities in thicker films required for scalable production, optical losses, and high series resistance of electrodes (Zhang et al., 2018; Mao et al., 2017; Lucera et al., 2017). The majority of reported efficiencies of OSCs or modules with an active area of 10–20 cm 2 range from 5% to 7.5%. Average PCEs of 3–4% were reached for solar cells with an active area of 20–50 cm 2 (Huang et al., 2019). Few papers reported large-area modules (> 100 cm 2 ) demonstrating reasonable efficiencies of 4.5–5.6% (Mao et al., 2017; Lucera et al., 2017; Berny et al., 2016). In this work, we report the synthesis of two novel conjugated polymers P1 and P2 comprising thiazolo[5,4-d]thiazole (Tz), benzo [1,2,5-c]thiadiazole (B), and thiophene (T) units and the fabrication of large-area photovoltaic cells and modules based on these polymers using slot-die coating as a roll-to-roll compatible and industry-relevant film deposition technique (Fig. 1). https://doi.org/10.1016/j.solener.2020.01.087 Received 29 October 2019; Received in revised form 5 January 2020; Accepted 31 January 2020 ⁎ Corresponding author. E-mail address: akkuratow@yandex.ru (A.V. Akkuratov). Solar Energy 198 (2020) 605–611 0038-092X/ © 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. T