| The research status of polymers solar cells(PSCs) and small molecular organic solar cells(SMs-OSCs) were summarized in this dissertation. In order to solve some key problems about SMs donor materials, such as narrow absorption spectra, low power conversion efficiency(PCE) and poor stability, three series of novel donor-acceptor(D-A) types small molecules(SMs) used as photovoltaic donor materials were designed and synthesized with anthracene and its derivatives(An), and diketopyrropyrroles(DPP). Their chemical structures were characterized by 1H NMR, time of flight mass spectrometry and elemental analysis, respectively. Furthermore, their thermal stabilities, as well as photophysical and electrochemical properties were systematically investigated. Using these SMs as donor and PC71 BM as acceptor, the bulk hetero-junction(BHJ) SMs-OSCs were made and their photovoltaic performances were further studied. The main research contents of this thesis are listed bleow.1. Two novel A-D-A type SMs of DPP2An(9,10) and DPP2An(2,6) were synthesized, in which two DPP were used as terminal acceptor(A) unit and 9,10- or 2,6- subsititued anthracene [An(9,10) or An(2,6)] were employed as central donor(D) unit, respectively. The effect of 9,10- and 2,6-subsititued positions of anthracene on photophysics, electrochemistry,crystallinity, hole mobility and photovoltaic performances were investigated. It is found that the SM of DPP2An(2,6) with 2,6-subsititued anthracene presented better properties. The DPP2An(2,6)/PC71BM(w/w,1:1) based SMs-OSCs by solution-processing displayed remarkably increased power conversion efficiency(PCE) of 5.44% with a short-circuit current density(Jsc) of 11.90 mA/cm2 and filled factor(FF) of 55.40 % under 1% 1,8-diiodooctane additive. The PCE and Jsc values here were 3.7 and 2.9 times of those corresponding values in the DPP2An(9,10)-based cells, respectively. And the highest hole mobility of 4.02×10-4cm2 v-1 s-1 was obtained in the hole-only DPP2An(2,6) based devices, which is two orders of magnitudes higher than that in the hole-only DPP2An(9,10) based one.2. Three novel D’-A-D-A-D’ type SMs of TDPP2 An, n-C8TDPP2 An and i-C8TDPP2 An were designed and synthesized, in which the terminal donor(D’) units of thiophene and alkylthrophene were appending into the end-group of the DPP2An(2,6), respectively. The effect of terminal D’ units on photophysics, electrochemistry, crystallinity, hole mobility and photovoltaic performances was investigated. It is shown that three D’-A-D-A-D’ type SMs showed narrowed optical gaps(1.65 eV to 1.69 eV). The terminal D’ units can extend the absorption spectra and decrease band-gap for their D’-A-D-A-D’ type SMs. Both SMs ofn-C8TDPP2 An and i-C8TDPP2 An with two terminal alkylthrophenes exhibited better photovoltaic performance with a PCE over 4.19% in their BHJ SM-OSCs.3. A class of one-dimensional(1-D) and two-dimensional(2-D) A-D-A type SMs of DPP2 AnOT, DPP2 AnAT and DPP2 AnST was synthesized, in which alkoxy, alkylthiophene and(alkthio)thiophene were attached into the 9,10-positions of DPP2An(2,6). And another class of 1-D and 2D Ar-A-D-A-Ar type SMs of P-DPP2 AnOT, P-DPP2 AnAT and P-DPP2 AnST was further prepared while phenanthrene(P) was appending into the terminals of DPP2 AnOT, DPP2 AnAT and DPP2 AnST, respectively. Their photophysics, electrochemistry, crystallinity, hole mobility and photovoltaic performances were investigated. It is demonstrates that six SMs here exhibited excellent carrier mobility. The DPP2 AnOT and DPP2AnAT-based SM-OSCs displayed better photovoltaic properties with a PCE over 3.83%.However, P-DPP2 AnOT, P-DPP2 AnAT and P-DPP2 AnST haven’t exhibited satisfactory photovoltaic properties with the maximum PCE of 2.38% due to their poor solubility and bad film morphology of the blend films... |
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