Thiophene and Naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole Based Alternating Copolymers for Polymer Solar Cells

Abstract

Two planar type photovoltaic polymers based on naphthobisthiadiazole, poly(2,5-bis(2-hexyldecyloxy)phenylene-alt-(5,10-dithiophen-2-yl)naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole) (hPPDTNTz) and poly(2,5-bis(2-decyltetradecyloxy)phenylene-alt-(5,10-dithiophen-2-yl)naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole) (d-PPDTNTz) were synthesized by incorporating intrachain noncovalent Coulombic interactions in the molecular design. To achieve a delicate balance of molecular weight, solubility as well as bulk film morphology, hexyldecyloxy (h-) and decyltetradecyloxy (d-) side-chains were substituted, which played a decisive role in modulating morphology, film packing structure and macroscopic device properties. Both polymers showed a broad light absorption up to ~800 nm and d-PPDTNTz exhibited a deeper HOMO and preferentially face-on orientation in pristine and blended films with PC71BM. The detailed optical, electrochemical, thermal, morphological and the resulting photovoltaic characteristics were studied. The best power conversion efficiency of ~6.7% was measured for d-PPDTNTz:PC 71 BM, suggesting that the careful choice of side-chains is necessary for fully optimize the photovoltaic materials and devices.

Noncovalent conformational locks in organic semiconductors

“…Inspired by this successful strategy of NCLs, Woo and coworkers [53] designed and synthesized another polymer (P16) by replacing 2FBT unit with a doubly fused BT unit, naphtha [1,2- In 2012, we designed and synthesized a new highly planar building block called diethoxy-substituted thienylvinylene (TVT) having intramolecular S•••O conformational locks, which offering opportunities to synthesize alkoxy-functionalized polymeric materials with low HOMO energies and good oxidative stability [18]. Based on this new building block, quite a few high performing conjugated polymers for OFETs and OSCs have been reported [39].…”