| In the last few years,the great success of nonfullerene acceptors（NFAs）has revived organic solar cells（OSCs）,and the highest power conversion efficiency（PCE）of OSCs has soared up to over 18%.This great breakthrough is based on the unique advantages of NFAs,such as low cost,broad and strong light absorption,tunable and suitable energy levels,and morphological stability.As far as we known,the highly efficient nonfullerene OSCs always employ wide-or medium-bandgap donor materials and low-bandgap NFAs for the complementary optical absorption.Therefore,development of low-bandgap NFAs have attracted extensive attention.1.A low-bandgap nonfullerene acceptors TIT-2FIC based on thieno[3,2-b]indole-thiophenes core had been developed.Compared with the similar NFAs DTC（4Ph）-4FIC with carbazole core,TIT-2FIC exhibited remarkable red-shifted absorption,and up-shifted HOMO energy levels as expected.In addition,TIT-2FIC showed great universal miscibility with nonfluorinated PBDB-T or Non-fluorinated PM6,therefore the corresponding OSCs both achieved promising PCEs of 11.80% or 13.00%,with higher photovoltage and photocurrent than those of the counterpart IT-4F-based cells.Furthermore,PM6:TIT-2FIC:Y6 based ternary solar cell pronounces a decent PCE of 17.22%,being significantly improved from that of 16.04% for the binary cell based on PM6:Y6.Similarly,this significant improvement also occur to ternary PM6:TIT-2FIC:IT-4F cell（14.46% vs13.41%）.These results indicated that TIT-2FIC possess good universality with nonfluorinated or fluorinated polymer donor materials in both binary and ternary cells.2.A new low-bandgap SMA TITT-2FIC based on thieno[2’,3’:4,5]thieno[3,2-b]indole was successfully synthesized.TITT-2FIC possessed the transitional chemical structure between ITIC series and the Y6 series NFAs.TITT-2FIC exhibited stronger intermolecular stacking and suitable energy levels.Furthermore,PM6:TITT-2FIC based binary solar cell pronounces a decent PCE of 12.26%.These results indicated that TIT-2FIC has great potential for OSCs. |
