Preparation And Performances Of Modified Carbon Aerogel Counter Electrodes And Polymer Photovoltaic Devices

In this dissertation, the basic structure, working principle and the latest researchprogress of the dye-sensitised solar cells (DSSCs) and polymer solar cells (PSCs)were briefly introduced. Recently, our study results indicated that the low-cost carbonaerogel electrode was an excellent substitute for Pt counter electrode of DSSC. In thisdissertation, carbon aerogels (CAs) with different pore structure were prepared byusing KOH as activation agent and introducing tripolycyanamide during the synthesisof organic aerogel precursors, and the effects of the pore structure of CAs on thephotovoltaic properties of DSSCs were studied. Synchronously, titanium (IV)isopropoxide (TTIP) was used as cathode interface layer of PSCs, and the invertedPSCs with the device structure of ITO/TTIP/P3HT：PCBM/MoO3/Al were firstlyprepared. The effects of TTIP layer on the photovoltaic properties of the PSCs werestudied. The main study results are shown as follows:1. CA3and CA4carbon aerogels were prepared by using acetyl trimethylammonium bromide as surfactant with different content. The DSSC based on CA4CEshows an approximate PCE value compared with the DSSC based on Pt CE under thesame experimental conditions. Activated carbon aerogels (ACAs) based on CA4wereprepared by using KOH as activation agent with different concentrations. Accordingto the results of N2adsorption measurement, the content of micropore and the specificsurface area of activated CA4have been largely improved. It was found that the PCEsof DSSCs based on the ACAs CE are all inferior to that of the DSSCs based on theCA4CE. The results of the electrochemical impedance spectroscopy indicate that theserials electric resistance (RS) and the charge transport resistance (RCT) of ACA CEsare larger than that of CA4CE, which indicates the electrocatalytic activity of theformer is lower than that of the later. The study results indicated that the content ofmicropore and the specific surface area caused by the micropore do not be in favor ofthe electrocatalytic activity of CE. In our opinion, the activation of CA4could lead tothe increase of the functional groups on the surface of ACAs, such as hydroxyl groupand carboxy group, which leads to the decrease of the adsorption capacity of I3-ionson the surface of ACAs and the conductivity. Therefore, the DSSCs based on ACACEs show poor photovoltaic performance.2. Nitrogen-doped carbon aerogels (NCAs) were prepared by introducing tripolycyanamide during the synthesis of organic aerogel precursors. The study resultsindicated that with the increase of nitrogen-doped concentration, the pore size ofNCAs decreases, and the mesoporous volume fraction increases, which lead to lowercharge-transfer resistance and better electrocatalytic activity. The NCA CE based onpolyvinylidene fluoride as binder shows a greater electrocatalytic activity than thatbased on polytetrafluorethylene because its higher polarity leads to better bondingcapacity. Under optimized experimental conditions, the DSSC based on flexibleNCA8CE achieved a photoelectric conversion efficiency (PCE) of8.83%, which is102.6%of that based on platinum CE (8.61%) under the same experimentalconditions (AM1.5,100mW/cm2).3. A solution processible TTIP was used as cathode interface layer in the invertedPSCs based on P3HT/PCBM. After optimized by the concentration, coating speed andannealing temperature of TTIP layer, the PCE of the inverted PSCs achieved3.54%,which is increased by51.3%in comparison with that (2.34%) of the conventionaldevice under the same experimental conditions (AM1.5,100mW/cm2). When theTTIP film is annealed in atmosphere surrounding or under high temperature, thetransmittance of TTIP film is reduces, the chemical structure of TTIP is changed, andthe LUMO energy level is raised, which lead to a decreased photovoltaicperformance.