The Investigation Of Buffer Layer In Organic Solar Cells And Perovskite Solar Cells

With the rapid development of the economy and the shortage of fossil fuels, the need for the development and utilization of new energy sources has become more urgent, solar cells based on photovoltaic technology emerged. On the consideration of market applications for solar cells, studies on solar cells at the targets of low cost, high efficiency and simple preparation process. Organic solar cells (OSCs) attract more attention for the advantages of light weight, low power for preparation and good flexibility. Perovskite solar cells become the new concerns in solar cells field for its low cost and high efficience. The working mechanism of solar cells is mainly composed of light absorption, excitons generation and dissociation, charge collection. In order to improve the efficiency of solar cells, methods of the structural design, control at the interface and surface morphology modification are mainly used. In this paper, buffer layers were introduced in organic solar cells and perovskite solar cells to get high pewer conversion efficience and simple preparation process. Details are as follows:(1) A new concept of strong electron acceptor molecule as a hole extraction layer (HEL) in organic solar cells (OSCs) is reported upon. The use of a dipyrazino[2,3-f:2’,3’-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) as a HEL between Al anode and the polymer active layer leads to highly efficient and stable OSCs. Different from the traditionally used p-type materials, the HAT-CN based HEL provides an efficient recombination zone for electrons injected from Al anode and holes extracted from the donor materials because of the suitable energy level alignment. An efficiency of 6.2% is realized for an inverted structure OSC with a blended poly(3-hexylthiophene) and indene-C60 bisadduct (P3HT:ICBA) active layer, which is comparable to the devices with a commonly used molybdenum trioxide (MoO3) HEL. As small molecule organic material, HAT-CN hole collection layer can be prepared at low temperature.(2) We constructed an effective electron extraction layer (EEL) used for polymer solar cells by integrating one new kind of organic material of 4,4-(1,4-phenylene) bis(2-phenyl-6-p-tolylnicotinonitrile) (p-PPtNT) and cesium carbonate (Cs2CO3) used as a compound EEL (CEEL). The CEEL based device exhibits an ideal PCE of 4.15%, corresponding to an enhancement 220% in contrast to that of control device without EEL, which is also comparable to that of ZnO based device. Our analyses indicated that the remarkably improved PCE for CEEL based device is mainly ascribed to the Ohmic contact and the negligible electron extraction barrier at cathode/active layer by inserting CEEL.(3) Buffer layers used in planar heterojunction perovskite solar cell were studied. The experiment introduce PEDOT:PSS material as HEL and PCBM material as EEL to replace spiro-OMeTAD and TiO2, respectively, which were used in conventional perovskite solar cells widely. We fabricate the planar heterojunction perovskite solar cell device with the structure of ITO/PEDOT:PSS/CH3NH3PbI3-xClx/PCBM/Ag. An efficiency of 11.02% is realized by optimizing the introduced interfacial buffer layer and the perovskite layer. By introducing PEDOT:PSS used as HEL and PCBM used as EEL, the planar heterojunction perovskite solar cell device can be fabricated with full-solution preparation process, which is more sample and cheap.