Two-photon Excited Fluorescence of Bithiophene Derivatives

Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit strong single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) with the emission peaks around ~560 nm and with the lifetime of ~1ns.

Revisiting the Bithiophene Imide-Based Polymer Donors: Molecular Aggregation and Orientation Control Enabling New Polymer Donors for High-Performance All-Polymer Solar Cells

Bithiophene imide (BTI)-based polymers have been promising photovoltaic materials due to their high mobility and tunable energy levels. However, BTI polymers have rarely been revisited since organic solar cells (OSCs) entered the era of non-fullerene electron acceptors (NFEA) likely owing to their incompatibility with NFEAs. Herein, fine-tuning the aggregation and orientation of BTI-based donor-π-acceptor (D-π-A) polymer donors was achieved by incorporating the linear n-octyl group into thiophene π-bridge. The resulting polymer donor G15 shows excellent compatibility with NFEA L15 (polymer acceptor). The G15-based all-polymer OSCs achieve high power conversion efficiency of 15.17%. This is significantly higher than that (< 5%) of its analogue with isomerized branched alkyl chains and also among the highest values for all-polymer OSCs. The results highlight that well-tailored BTI polymer donors are attractive photovoltaic materials for further exploration in non-fullerene organic solar cells.

Enhancement the photovoltaic performance of conjugated polymer based on simple head-to-head alkylthio side chains engineered bithiophene

In this article,three novel and simple molecular structure with donor-acceptor(D-A) type copolymers via only head-to-head alkoxy(OR) and/or alkylthio(SR) side chains onto the bithiophene(BT) as donor units and fluorinated benzotriazole(FBTA) as acceptor unit,namely,PBTOR-FBTA,PBTOSR-FBTA and PBTSRFBTA,were successfully designed and synthesized.The impacts of sulfur-oxygen(S…O) or sulfur-sulfur(S-S) noncovalent interactions on their physicochemical properties,molecular stacking,carrier mobility,morphologies of blend films,as well as their photovoltaic performance were deeply and systematically studied.The introduction of SR side-chains suddenly lowered the highest occupied molecular orbital(HOMO) energy levels,blue-shifted absorption,enhanced π-π stacking,as well as improved morphology of the photoactive layer blends in comparison with the re ference polymer without SR side-chain.Polymer solar cells(PSCs) were fabricated to estimate their photovoltaic performance of the polymers.Under an optimized blend ratio of PBTSR-FBTA:PC71BM(1:0.8,w/w),the PBTSR-FBTAbased device exhibits a higher power conversion efficiency(PCE) of 6.25%,which is about 3.34 and 1.87 folds than that of the PBTOR-FBTA and PBTOSR-FBTA-based devices,respectively.Our research results demonstrate that the modification of the simple and low-cost SR side chains is an effective strategy to improve the photovoltaic performance of the polymers.