Binary and Ternary Polymer Solar Cells Based on a Wide Bandgap D-A Copolymer Donor and Two Nonfullerene Acceptors with Complementary Absorption Spectral.

Abstract

A new wide-bandgap conjugated D-A polymer denoted as P106 with a medium acceptor dithieno [2,3-e;3'2'-g]isoindole-7,9 (8H) (DTID) unit and strong 2-dodecylbenzo[1,2-b:3,4-b':6,5-b"]trithiophene (3TB) donor units shows an optical bandgap of 2.04 and highest occupied molecular orbital energy level of -5.56 eV. P106 is used as the donor and two nonfullerene acceptors-medium bandgap DBTBT-IC and narrow band Y18-DMO-are used as acceptors for the construction of binary and ternary bulk heterojunction polymer solar cells. The optimized polymer solar cells based on P106 : DBTBT-IC and P106 : Y18-DMO exhibit power conversion efficiencies of 11.76 % and 14.07 %, respectively. The short-circuit current density (22.78 mA cm-2 ) for the P106 : Y18-DMO device is higher than that for P106 : DBTBT-IC (18.56 mA cm-2 ) one, which could be attributed to the more photon harvesting efficiency of the P106 : Y18-DMO active layer. In light of the high short-circuit current densities and fill factors for the Y18-DMO based device and the high value of open circuit voltage of the DBTBT-IC based device, ternary polymer solar cells are fabricated by using ternary active layer (P106 : DBTBT-IC : Y18-DMO) and achieve a power conversion efficiency of 16.49 % with low energy loss of 0.47 eV.