Abstract
The object of this thesis is to enhancement of the device performances of tandem polymer and perovskite solar cells, and the contents are divided into three topics. In the first two sections, we study on the film formation quality of aqueous hole-transport interlayer on hydrophobic active layer in the inverted tandem polymer solar cells, leading to significantly elevated performance for the large area devices. In the last section, we obtain high performance of perovskite solar cell by solvent annealing of the PbI2 film, and realize the growth mechanism of perovskite with dipping in various concentrations of CH3NH3I (MAI). In chapter 5, we propose the deposition of ultra-thin silver or gold layer (in subnano-scale) between bottom subcell and the hole-transport sublayer in the interlayer (IL), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), in the inverted tandem polymer solar cell (t-PSC) for improving the wettability of aqueous hole-transport interlayer on hydrophobic active layer. The ultra-thin sliver layer can improve device performance, but the ultra-thin gold layer induces a significant decrease of ionized potential from 4.54 eV to 4.14 eV leading to an accumulation of holes at (regioregular poly(3-hexylthiophene) (P3HT) side in the interface of P3HT/PEDOT:PSS, which decreases the device performance. In the inverted t-PSCs (small-area, 0.02 cm2) composed of the bottom subcell P3HT: indene-C60-bisadduct (ICBA)), the top subcell (thieno[3,4-b]thiophene/benzodithiophene (PTB7) with [6,6]-phenyl C71-butyric acid methyl ester (PC71BM)) and the IL, PEDOT:PSS/ZnO nanoparticles, the power conversion efficiency (PCE) is improved from 7.06 % (without any ultra-thin metal layer) to 7.81 % with 0.5 nm Ag layer but decreases to 6.4 % with 1nm Au layer. As enlarging the active area to 1 cm2, the PCE of 0.5 nm Ag device is still over 6 % (6.11 %) much higher than that without Ag layer (2.19 %) by a factor of 2.78. In chapter 6, we treat the active layer (P3HT:ICBA) surface by alcohols for hydrophiles leading to high-quality film of the next spin-coated PEDOT:PSS layer. For the small-area (0.02 cm2) inverted t-PSC, the PCE can be enhanced from 7.06 % to 8.10 % by 1-hexanol treatment. As enlarging the active area to about 1 cm2, the device with 1-hexanol treatment still performs 7.00 % high PCE, which is much better than that without any treatment (2.19 %). In addition, the main advancement of this work is the use of low cost material (1-hexanol) and low cost fabrication process (spin coating) as compared to depositing 0.5 nm Ag layer on active layer, in which the high cost material (silver) and high cost deposition process (vacuum thermal deposition) are used. In chapter 7, we demonstrate that treatment of the PbI2 films with solvent annealing can change the surface morphology with large and deeper porous due to increasing PbI2 crystallinity. For PbI2 film dipped into 10 mg/mL CH3NH3I (MAI) solution, crystals of CH3NH3PbI3 are quickly formed on the surface of PbI2 and inhibit MAI to further penetrate into the PbI2 film. Therefore, PbI2 film with large and deep porous surface can form more crystals of CH3NHPbI3. The PCE of the device with solvent annealing treatment for over 5 min is enhanced from 1.08 % to 16.07 %. For PbI2 film dipped into low concentration 6 mg/mL CH3NH3I (MAI) solution, crystals of CH3NH3PbI3 form slowly on PbI2 surface, which provide the MAI enough time going through surface to inside PbI2 film. Thus, the PCE of solvent annealed treatment device (14.3 %) is similar to that without treatment (13.37 %), demonstrating that the factor of the PbI2 morphology can be minimized.