Performance Optimization Of Polymer Solar Cells And Synthesis&Properties Of Benzothiadiazole Derivatives With A D-A-D Structure Used As Photovoltaic Materials

Organic/polymeric solar cells have received much attention due to their low productioncost, flexible cell, and relatively high power conversion efficiency. In this dissertation, theoperating principle and development of organic solar cells (OSCs) and polymeric solar cells(PSCs) were introduced in details. In order to overcome these problems, such as lowefficiency and lifetimes for OSCs and PSCs, both the performance optimization of the PSCsused poly side-chain benzodithiophene-alt-thiophene derivatives of PBDT-TDPP as donormaterial and synthesis&properties of the benzothiadiazole derivatives with a D-A-D struc-ture used as organic photovoltaic materials were systematically investigated by device pro-cessing and molecular design. The main research results are listed below.(1) The performance optimization of the PSCs used poly side-chain benzodithiophene-alt-thiophene derivatives of PBDT-TDPP as donor material was firstly studied. A series ofphotovoltaic devices using the side-chain D-A-based PBDT-TDPP as donor and the fullerenederivatives as acceptor were fabricated with a conventional structure of ITO/PEDOT:PSS/Active Layer/Interface Modification Layer/Al. The device performance was optimized bychanging acceptors, the ratios between donor and acceptor, solvents, active layer thickness,organic surface layer, annealing time and temperature. The high-performance polymer solarcell with power conversion efficiency (PCE) up to6.98%was obtained by device optimi-zation under the simulated sunlight illumination AM1.5(100mW/cm~2).(2) The synthesis and properties of the benzothiadiazole derivatives with a D-A-D struc-ture used as organic photovoltaic materials were also investigated at the same time. A seriesof the donor-π-acceptor-π-donor (D-π-A-π-D)-based benzothiadiazole derivatives were syn-thesized used as organic photovoltaic donor materials, in which benzothiadiazole (BT), fluo-rene and thiophene were used as acceptor, donor and π bridged units, respectively. All ofthese D-A-D-based organic small molecules were confirmed by1HNMR and MALDI massspectrometry (MS). Their optical and thermal properties, as well as their liquid crystalline,electrochemistry and mobility properties were measured. Used these (D-π-A-π-D)-basedbenzothiadiazole derivatives as donor and PC61BM as acceptor, some bulk heterojunctionOSCs were made by solution processing. The influence of liquid crystal and alkyl chain ofthese donor molecules on photovoltaic performance were discussed. While (C8Fl-Th)2BT wasused as donor, the device exhibited a highest PCE of0.96%. While the PC61BM was placed byPC71BM, the device displayed an increased PCE of1.92%and a high open-circuit voltage (Voc)of0.92V under the simulated sunlight illumination AM1.5(100mW/cm~2). Interestingly, the (C8Fl-Th)2BT with liquid crystal exhibited not only good thermostability and hole mobility,but also best photovoltaic performance in these BHJ-OSCs.