Designing alkoxy-induced based high performance near infrared sensitive small molecule acceptors for organic solar cells

Abstract

Scientist are dedicated to design and synthesize efficient photovoltaic materials to overcome the energy crises. In this regard, herein, we have designed four new small acceptor molecules namely ( A1, A2, A3 and A4 ) for better performance in organic solar cells. These molecules consist Alkoxy-Induced Naphtho-dithiophene core unit flanked with 2,2-ethylidene-5,6-dicyano-3-oxo-2,3-dihydroinden-1-ylidene-malononitrile ( A1 ), methyl-2-cyano-2,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-acetate ( A2 ), 5,2-ethylidene-5,6-difluoro-3-oxo-2,3-dihydroinden-1-ylidene-3-methyl-2-thioxothiazolidin-4-one ( A3 ) and 2,5-ethylidene-6-oxo-5,6-dihydrocyclopenta-thiophen-4-ylidene-malononitrile ( A4 ) end-capped acceptor groups. Their optical, electrical and geometries have been compared with reported molecule R. Frontier molecular orbital diagram reveal excellent charge transfer rate, The electron density is shifted from donor to acceptor unit. Among all, A1 exhibits the highest absorption in the visible region (λ max ) at 798 nm in chloroform solvent. The maximum open circuit voltage (2.08 V) is observed for A3 when blended with PTB7-Th donor polymer. All studied molecules have high charge mobilities due to lower reorganization energy values with respect to model molecule R . A1 has the highest electron mobility among all molecules due to lower value of reorganization energy which is 0.0034. Furthermore, all designed molecules show good Solubilities in organic solvent. A2 exhibit high value of dipole moment which reveal good solubilities in fabrication process. We have designed four ( A1, A2, A3 and A4 ) fused ring electron acceptor for their use in OSCs. These molecules contain Alkoxy-Induced Naphtho-dithiophene core unit attached with different acceptor groups to enhance PCE of OSCs. All newly designed molecule have better performance as compared to R . Additionally, A1 exhibits strong absorption in visible region in both gas phase (λ max = 724.1 nm) and solvent (λ max = 798.4 nm) and exhibit lowest energy band gap (1.92 eV). • A1 shows the highest absorption maximum (λ max ) 798.4 nm in chloroform solvent. • The Designed molecules are blended with well-known donor polymer PTB7-Th. • All designed molecules have lower binding energy as compared to reference molecule R. • All newly designed molecules have excellent opto-electronic properties with respect to R.