Preparation On Carbon Back Electrode For Perovskite Solar Cells

In conventional Perovskite solar cells (PSCs), organic p-type semiconductors are usually used to extract holes, then being collected by Au or Ag thin film cathode that can be fabricated by thermal evaporation deposition. Presently, the widely used organic material for hole-transport layer is spiro-MeOTAD, which is not only expensive but also shows inferior stability. On the other hand, high-vacuum techniques are usually needed for fabrication of Au or Ag cathode for PSCs, also unsuitable for commercial and large-scale manufacture. Hence, it is ungently desired to seek suitable cathode materials to ensure both photovoltaic performance and enhancement in PSCs stability, enabling them for future large-scale production.In this thesis, with the aim at reducing the production cost of PSCs and enhancing their stability, we focus our researches on developing carbon back electrodes for PSCs, for example, research on the influence of material type, structure and fabrication method on the photovoltaic performance of PSCs. Meanwhile, we give analysis to some important findings, details are listed as follows:(1) We researched on fabrication of carbon paste that was suitable for printing. Results showed that the as-obtained carbon paste had very poor conductivity, unsuitable for serving as back electrode for PSCs. We carried our research that showed that, when adding large-sized needle-coke, the conductivity of the carbon back electrode could be enhanced and the power conversion efficiency (PCE) is 0.53%. After analysis, we found that the difficulty in film thickness control, as well as the poor interfacial contact finally resulted in inferior photovoltaic performance of PSCs.(2) We researched on replacing doctor-balding with spray for fabrication of carbon back electrode for PSCs, by which the photovoltaic performance was enhanced obviously and the highest efficiency is 3.9%. To improve the contact between carbon black nanoparticles, we used mechanic pressure treatment to enhance the conductivity and the cell performance. Besides, we researched the fabrication of composite as carbon back electrode for PSCs. Results showed that using CNTs alone as back electrode gave poor performance. When composited with carbon black, the cell performance was enhanced obviously and the PCE is 6.57%.(3)We researched on using needle-coke as source for fabrication of carbon back electrode for PSCs. Temperatures of thermal treating needle-coke samples were optimized, we found that the one treated at 1500℃ had the smallest resistance, suitable for fabrication of carbon back electrode for PSCs. In addition, we found that, due to moisture, perovskite could be easily damaged when using spray in air. The stability test to PSCs was conducted, after 8 days, no decrease on cell PCE was found.(4) We researched the effect of thermal treating of PSCs on the device stability and found that the highest PCE can reach 8.57% after thermal treating. By some characterizations, we conclude that the needle-coke-based electrode might protect perovskite from being etched by external unfriendly atmosphere, meanwhile, by which the crystallinity of perovskite could be improved. Our analysis could be used to interpret why the absorption property and the cell performance were improved after thermal treating. Our research offers new strategy for improving the photovoltaic performance of PSCs.