A bis(diketopyrrolopyrrole) dimer-containing ligand in platinum(ii) polyyne oligomers exhibiting ultrafast photoinduced electron transfer with PCBM and solar cell properties. Issue 7 (17th January 2020)

• Record Type: Journal Article
• Authors: Nos, Mélodie; Marineau-Plante, Gabriel; Gao, Di; Durandetti, Muriel; Hardouin, Julie; Karsenti, Paul-Ludovic; Gupta, Gaurav; Sharma, Ganesh D.; Harvey, Pierre D.; Lemouchi, Cyprien; Le Pluart, Loïc
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 7(2020)
• Page Start: 2363
• Page End: 2380
• Publication Date: 2020-01-17
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc03487k
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : We report the synthesis and characterization of a bis(diketopyrrolopyrrole) dimer-containing ligand in platinum(ii ) polyyne oligomer P4 with very good photovoltaic performance, PCE = 9.54% (P4 ; J sc = 16.24 mA cm −2, V oc = 0.89 V, FF = 0.66). Abstract : Two polyyne oligomers using the thiophene–(diketopyrrolopyrrole)–thiophene unit, T–DPP–T, and the organometallic synthon trans -Pt(PBu3 )2 (CC)2, [Pt], ([L1]–[Pt]) m (P1 ), here used for comparison purposes, and ([L4]–[Pt]) m (P4 ), where L1 and L4 are T–DPP–T and (T–DPP–T)2, respectively, were synthesized by CuI-catalyzed dehydrohalogenation and fully characterized. The optical and electrochemical properties were investigated by UV-visible absorption and cyclic voltammetry, and P4 was found to exhibit a very low band gap. DFT (density functional theory) and TD-DFT (time-dependent DFT) computations were undertaken to address the polymers' geometry, their electronic structures and calculated HOMO and LUMO energies. The S1 level is best described as a ππ* excited state. P1 and P4 exhibit fluorescence lifetime in ps timescale and the fs-TAS data indicate an ultrafast electron transfer to PC61 BM (( 1 P x * + PC61 BM → P x + ˙ + (PC61 BM) − ˙; time scale < 113–128 fs) evidenced by an increased formation of the triplet state upon back electron transfer (P x + ˙ + (PC61 BM) − ˙) → 1, 3 P x * + PC61 BM; x = 1, 4). The timescale of recombination for P4 (P4 + ˙ + (PC61 BM) − ˙ → 3 P4 * + PCBM) is found to be ∼3 ps. The photovoltaic performance of P x was investigated by fabricating the photovoltaic solar cells (PSCs) with conventional device structure ITO/PEDOT:PSS/(P1 or P4 ):PC71 BM/PFN/Al. After solvent vapour annealing with THF, the power conversion efficiencies, PCEs, are 7.36% (P1 ; J sc = 12.94 mA cm −2, V oc = 0.92 V, FF = 0.62) and 9.54% (P4 ; J sc = 16.24 mA cm −2, V oc = 0.89 V, FF = 0.66). The higher PCE of P4 may be related to the faster extraction and longer charge carrier lifetime for P4 based PSCs as compared to P1 .