A new type of pyranthrene-based copolymer as a promising hole-transport material for perovskite solar cells†

Perovskite solar cells (PSCs) with an n–i–p configuration have demonstrated rapid progress in the past few years, though the most efficient devices were made using a doped small molecular hole-transport material, spiro-OMeTAD, which deteriorates their long-term stability. To address this problem, dopant-free hole transport materials should be developed. Herein, we present the synthesis and characterization of poly(4-(5′-(16-(3,4′-bis(2-ethylhexyl)-[2,2′-bithiophen]-5-yl)pyranthrene-8-yl)-3′,4-bis(2-ethylhexyl)-[2,2′-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole) (PATTBTT), which is considered as a promising hole-transport material for PSCs. The designed copolymer PATTBTT delivered a power conversion efficiency of 17.6% in PSCs, which was higher than those obtained for reference devices fabricated using dopant-free polytriarylamine-based hole-transport materials. These results demonstrate that pyranthrene-based conjugated polymers represent a promising new family of materials for high-efficiency perovskite solar cells.