Research On Solvent And Additive Used In Polymer Bulk-heterojunction Solar Cells

Solar cells are part of the renewable energy. Since the1950s, many types of solarcells are being studied. And now the primary commercial silicon solar cells havedisadvantages of complex manufacturing process, high production costs andcumbersome, while not being large-scale used. Polymer-based bulk heterojunction solarcells have the potential of flexible, lightweight, easy to mass production and low powergeneration cost, while are being extensively studied.In this thesis, the classification criterions of based on the photosensitive layermaterial, based on the interface energy level and based on the structure were reviewed.The novel host solvent, ternary solvents were investigated in polymer-fullerene solarcells. Novel donor polymers were optimized. Solvent additives were used in thepolymer-quantum dot hybrid solar cells to enhanced the performance.In P3HT-PCBM system, unconventional solvent bromobenzene (BrB) wasemployed to replace conventional chlorinated solvent chlorobenzene (CB), jointadditive diiodooctane (DIO), the efficiency increased from2.79%to3.14%. Comparingto CB/DIO, BrB/DIO cast blend film shows more optimized phase separation, thus canget more ideal diode characteristics and higher efficiency. And this method is also usedin several novel polymer-PCBM system which also get better results relative toconventional CB/DIO.Ternary solvents CF/o-DCB/DIO were used to fabricate novel polymer-fullerenethin film solar cells. It was found that if the polymer solubility in CF and o-DCB aresimilar, CF/DIO and o-DCB/DIO solution need higher and lower optimization rotate speed separately, and when mixed CF/o-DCB solvents were used, optimization speedapproaches average, however, when the polymer solubility difference in CF and DCB isobvious, the DCB solution usually is very viscous, which also need high rotate speed toget uniform film, then it’s needless to adjust the spin speed again when ternary solventswere used.Two series of novel polymer donors were optimized by solvent selection andadditives, the device efficiency of two systems reached5.1%and2.6%respectively.Mobility and morphology characterization measurements explain the impact of thedevice fabrication methods on the performance of the devices.Oleic acid-capped quantum dots have different dissolution properties compare tofullerene derivatives. The efficiency increased from0.4%to1.5%when additiveschlorooctane and dichlorooctane were added into the P3HT-PbS QDs solution. Analysisshowed that additives can facilitate the crystallization of P3HT, improve the absorptionof light and increase the hole mobility, while the electron mobility is constant, thepolymer-QD phase separation becomes small. And when thermal annealing were alsoadopted, these parameters can be further optimized and device efficiency improved upto2.7%.