Ultra-flexible high-efficiency organic solar cells based on polyimide electrodes and all-polymer blends

Ultra-flexible all-polymer solar cells (all-PSCs) are increasingly attracting attention as a complementary technology to traditional solar cells. This study developed mechanically durable ultra-flexible transparent conducting electrodes (TCEs) made of polyimide (PI)/silver nanowire (AgNW), which were integrated into all-PSCs. Tensile and bending tests showed that the PI/AgNW TCE displayed higher flexibility and stability than the commercial polyethylene terephthalate (PET)/indium tin oxide (ITO) with R₀/R₃₀₀₀₀ of 1.0, Young modulus of 176.7 MPa, and elongation at break of 12.8%. When combined with the non-fullerene polymer acceptor, the all-polymer 9′-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9,9′′-diphenyl-9H,9′H,9′′H-3,3′:6′,3′′-tercarbazole (PM6):regio-regular polymer acceptor (PYF-T-o) device exhibited highly improved flexibility, maintaining a power conversion efficiency of 12.42% by 99.3% after 800 bending cycles. This performance far surpassed that of small molecule non-fullerene acceptor PM6: 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]-thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (Y6) devices using PET/ITO and PI/AgNW TCEs. The toughening mechanisms of TCEs and devices were further analyzed through finite element simulations, highlighting the importance of optimizing the mechanical properties of both the TCE and the active layer. This study underscores the significant potential of PI/AgNW-based all-PSCs in the field of ultra-flexible solar cells.