| Over the past two decades,organic/polymer photovoltaic devices have received great attentation due to advantages of low-cost,light-weight,large-area processing etc.With the rapid development of novel conjugated polymers with excellent performance,the power conversion efficiency(PCE)of organic/polymer photovoltaic devices improves quickly and gradually approaches the commercial threshold of organic/polymer photovoltaic devices.Organic/conjugated materials with water/alcohol solubility exhibit a wide range of applications due to their excellent photoelectric properties,unique solubility in polar solvents,excellent electron transport properties etc.This dissertation mainly deals with the development of water/alcohol conjugated polymer with aim to study their doping properties,photoconductivity,electron mobility and photovoltaic properties.In the second chapter,we developed a water/alcohol soluble polymer(PN4N)which can be used as reducing agent and stabilizer to control the growth of Au nanoparticles.The synthesized Au NPs show good uniformity in size and shape and the prepared Au nanoparticles doped PN4 N hybrid composites exhibit high stability.Amine-containing polymers are good electron transport materials(ETMs)in photovoltaic devices and planar heterojunction perovskite solar cells.The performance of the photovoltaic devices with Au NPs doped PN4 N based ETMs are largely improved when compares to devices with pristine PN4 N due to the enhanced charge collecting properties of the doped PN4 N.Furthermore,by incorporating larger Au NPs into PEDOT:PSS to enhance the absorption of the light harvesting layer,PCEs of 6.82% and 13.7% can be achieved for photovoltaic devices with PCDTBT/PC71 BM as the light harvesting materials and CH3NH3 Pb I3-x Clx perovskite layer,respectively.In the third chapter,we designed and synthesized a series of cationic phosphonium conjugated polyelectrolytes(CPCPs)with different counter anions.The CPCPs are soluble in environmentally friendly polar solvents,which can enable the fabrication of multi-layer organic optoelectronic devices.Besides,the CPCPs show better thermal stability than traditional quaternary ammonium salt based conjugated polyelectrolytes.The CPCPs perform efficiently as electrode modifiers to lower the work function of metal electrode and can increase the photovoltaic performance.Significant enhancement in PCE from 6.3% to >9.0% were achieved by employing a thin layer of CPCPs between active layer and Al electrode in polymer solar cells with conventional device structure.Moreover,the CPCPs can be used as dopants to Zn O,and the doped ZnO can improve the interface contact between bottom contacts and active layer in inverted solar cells,resulting in improved photovoltaic performance.In the fourth chapter,we designed and synthesized a series of ion-containing n-type polyelectrolytes using in situ quaternisation polymerisation and ion-exchanging processes.The polyelectrolyte prepared through quaternisation polymerisation is endowed with good water solubility immediately.Moreover,the attached anions of the polyelectrolytes can be easily exchanged into other anions,which induces controllable doping and self-assembly in their deposited film.The results of the optical absorption and electron paramagnetic resonance study show that polyelectrolytes with F-,OH-,and CH3COO-as anions are strongly self-doped,and polyelectrolytes with Cl-,Br-,and I-possess weak self-doping properties.The space-charge limited current study shows that the charge mobilities of these polyelectrolytes correlate with their doping behaviours.Furthermore,the film morphology of these polyelectrolytes can be fine-tuned by the anions.In particular,PPDI-Ac with CH3COO-can self-assemble into nanowires in thin films,which contributes to its higher mobility than that of polyelectrolytes with other anions.These polyelectrolytes can be utilised as thickness-insensitive ETMs to fabricate high-performance photovoltaic devices.When the thickness of these polyelectrolytes is up to 50 nm,the PCEs of photovoltaic devices with the polyelectrolytes can be over 8%,indicating that these polyelectrolytes are promising candidates as ETMs for fabricating largearea photovoltaic devices via roll-to-roll processing.In the fifth chapter,we develop a series of tailor-made n-type water/alcohol soluble conjugated polymers that comprise different conjugated backbones and pendant polar groups and systematically study the relevance of the doping properties and structures of n type water/alcohol soluble conjugated polymers.We find that the doping behaviour and photoconductivity of these polymers correlated significantly with the electron affinities of their backbones and electron-donating strengths of their pendant polar groups.Moreover,the electron-only device study results indicate that counterions with stronger electron-donating abilities could improve the electron mobility of these polymers.Importantly,an n-type backbone with better planarity and a higher affinity would more strongly benefit the self-doping process and higher charge transport properties of n-type water/alcohol soluble conjugated polymers,leading to improved performance in photovoltaic devices.When used as ETMs in photovoltaic devices,these n-type water/alcohol soluble conjugated polymers can yield high power conversion efficiencies exceeding 10% and 9% for photovoltaic devices with 5-to 10 nm and 60-nm n-type water/alcohol soluble conjugated polymers,respectively.In the sixth chapter,we develop a series of tailor-made n-type water/alcohol soluble conjugated polymers with tunable absorption spectra by copolymerizing electron-deficient naphthalimide monomer with thiophene monomers with different electron-donating strength.The absorption of these polymers can be extended to 1300 nm and the absorption in the visable range is much reduced.Thus,the absorption compeletion between the active layer and electron trnaposrt layer is much avoided.These n-type water/alcohol soluble conjugated polymers can be used as a thick ETMs for polymer photovoltaic devices with PCEs of more than 10%. |
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