Solar Energy, Vol.201, 489-498, 2020
Highly thermally stable all-polymer solar cells enabled by photo-crosslinkable bromine-functionalized polymer donors
Here, high performance polymers bearing photo-crosslinkable function are developed for all-PSCs to achieve both high efficiency and stability. Then, a series of novel -(D-A)(a)-(D-D-1)(b)-type photo-crosslinkable bromine (Br)-functionalized polymer donors PBDT(T)FTAZ-B-X were synthesized, in which typical benzodithiophene (BDT) derivative was as first component (D), thiophene-difluro-benzotriazole (FTAZ) derivative was as second component (A), new simple BDT-based functionality appended Br-unit synthesized in this study was as third component (D1). The effects of Br-functionalized component on the photoelectric properties of the polymers were investigated. Moreover, UV-mediated photo-crosslinking effects on performance and thermal stability were thoroughly explored. All-PSCs based on these photo-crosslinkable polymers and N2200, but without photocrosslinking, displayed a highest PCE of 7.21%, which was achieved by an optimized PBDT(T)FTAZ-B-5-based device. As results, photo-crosslinked PBDT(T)FTAZ-B-5 + UV5min-based devices afford extraordinarily excellent thermal stability, in which high retention rate of 91.8% of the maximum PCEavg and the intrinsic performance (PCEmax: 6.12%) are maintained even after 72 h 150 degrees C annealing. For comparison, reference PBDT(T)FTAZbased devices only display PCEmax value of 5.13% and retain 84.2% of their maximum PCEavg under same aging. This contrasting result indicates that developing photo-crosslinkable Br-functionalized polymers is an effective strategy to further advance in both stability and efficiency of all-PSCs.