| Solar cells are presently considered as an important source of renewable and green energy to solve the energy and environment crisis. Organic solar cells have multiple advantages such as low-manufacturing cost, compatibility with flexible substrates, easiness of fabrication and large-area fabrication. The power conversion efficiency of perovskite solar cell exhibits a a significant improvement from 3.8% to 22.1% in the past six years. The perovskite solar cell showed a big potentiality for commercial applications, attracted increasing attention in the field of photovoltaic kingdom. The article was separated from two aspects as follow:1. We present the thickness-dependence of the performance of planar heterojunction organic solar cells(OSCs) with 1,4,5,8-napthalene-tetracarboxylic-dianhydride(NTCDA) as interlayer between rubrene/C70. The S-shaped current-voltage(J-V) characteristic is observed in the optimization process of NTCDA thickness. With the increase of NTCDA thickness, device performance first increase then decrease, with the optimum thickness of 15 nm, and the highest PCE of 1.03% is obtained for the device. The observed thickness-dependence of S-kink is totally different from previous reports of BCP based OSCs. The anomalous J-V characteristics were investigated by using the impedance-potential technique. We find that larger impedance occurred in the device with thinner NTCDA interlayer, and the mechanism could be described by charge distribution between the interface of C70 and Al cathode. Finally, we propose an effective approach to eliminate the S-kink in J-V curves by post annealing processes.2. The devices with the structure of FTO/TiO2/perovskite/HTMs/Mo O3/Ag were fabricated. The performance of devices with different dopant-free polymer hole transporting layers were also investigated. The HOMO level and interface contact of polymeric layers mainly affected the performance of device. We find that PTh4 provides the highest efficiency(13.19%) among the polymeric HTMs examined, with higher FF and Voc values than devices based on other polymers. |
