Study On Polymer Solar Cells With MoO₃as Anode Buffer Layer

MoO3as an efficient anode buffer layer (ABL) is widely used in polymer solar cells (PSCs). This paper mainly focus on these aspects:different preparation methods, appropriate modification, composite anode buffer layer of MoO3with other materials, and the influence on the performance of polymer photovoltaic devices. The main results are as follow:1. MoO3and CuPc as the composite ABL in PSCsThe PSCs with a structure of FTO/MoO3/CuPc/P3HT:PCBM/Al have been fabricated using poly(3-hexylthiophene)(P3HT) as the electron donor,[6,6]-phenyl C61butyric acid methyl ester (PCBM) as the electron acceptor, P3HT:PCBM bulk heterojunction (BHJ) as the polymer active layer (PAL), and MoO3deposited by magnetron sputtering and CuPc deposited by thermal evaporation as composite ABL. MoO3layer was found to be critical to the device performance, effectively extracting holes to prevent the exciton quenching and reducing the interfacial resistance because of alignment of energy levels. The introduction of CuPc buffer layer was observed to be ameliorative for device performance, further enlarging the visible absorption spectra range of the devices. The effect of the MoO3and CuPc layer thickness on device performance was studied. The optimized thickness was achieved when MoO3layer was12nm and CuPc layer was6nm, resulting in optimized power conversion efficiency (PCE) of3.76%under AM1.5G100mW/cm2illumination.2. MoO3treated by UV-ozone as the ABL in PSCsThe PSCs with a structure of FTO/MoO3/P3HT:ICBA/LiF/Al have been fabricated using P3HT as the electron donor, indene-C6o bisadduct (ICBA) as the electron acceptor, P3HT:ICBA BHJ as the PAL, MoO3deposited by magnetron sputtering and treated by UV-ozone (UVO) as the ABL, and LiF as the cathode buffer layer (CBL). LiF is observed to be critical for the device performance, significantly enhancing the fill factor (FF) and the efficiency compared to the device without LiF layer. After UVO treatment on MoO3film, its surface morphology, transmittance and film quality can be improved, therefore, it is beneficial to the performance of the PSCs. The optimal thickness of MoO3and UVO treatment time on MoO3was12nm and15min, respectively. Based on these optimal parameters, a PCE of6.43%was obtained under AM1.5G100mW/cm2illumination.3. Solution processed MoO3treated by UV annealing as the ABL in PSCsThe PSCs with a structure of FTO/s-MoO3/P3HT:ICBA/LiF/Al have been fabricated using P3HT as the electron donor, ICBA as the electron acceptor, P3HT:ICBA as the BHJ PAL, Solution processed MoO3(s-MoO3) treated by UV annealing as the ABL, and LiF as the CBL. A facile and cost-effective preparation method was used to obtain the MoO3aqueous solution and the S-MoO3thin film by thermal decomposition of (NH4)6Mo7O24·4H2O. The s-MoO3ultra-thin film was treated by three annealing mode for comparison:no annealing,100℃thermal annealing and UV annealing. By UV annealing treatment, the transmittance, surface morphology and film quality of s-MoO3film can be enhanced which is favorable to the performance of devices. So, the device based on s-MoO3by UV annealing can get a better performance than that by other two annealing mode and obtain comparable or even a little better performance than that based on PEDOT:PSS. On the other hand, the device stability based on s-MoO3by UV annealing is a little better than that based s-MoO3by no annealing or thermal annealing and much better than that bassed PEDOT:PSS.4. MoO3/Au/MoO3as the composite ABL in PSCsThe PSCs with a structure of FTO/MoO3/Au/MoO3/P3HT:PCBM/LiF/Al have been fabricated using P3HT as the electron donor, PCBM as the electron acceptor, P3HT:PCBM as the BHJ PAL, MoO3/Au/MoO3as the composite ABL, and LiF as the CBL. MoO3itself is an effective ABL. The introduction of an ultra-thin Au film can make full use of its high work function, high conductivity, good chemical stability, and high transmittance so as to improve the performance of the composite ABL, eventually enhance the PCE and stability of PSCs.5. MoO3as the ABL in novel polymer system solar cellsThe PSCs with a structure of FTO/MoO3/PBDTTT-C-T:PC71BM:DIO/LiF/Al have been fabricated using PBDTTT-C-T as the electron donor, PC71BM as the electron acceptor, PBDTTT-C-T:PC71BM as the BHJ PAL, MoO3as the ABL, and LiF as the CBL. MoO3was used instead of PEDOT:PSS in the references for the novel polymer system solar cells in order to try obtaining the comparable PCE than that of PEDOT:PSS. The optimum PCE is discussed by changing the thickness of the MoO3film layer. The result is that the best PCE is6.13%when the optimal thickness of the MoO3film layer is10nm.