Investigation On The Small-molecule Organic Photovoltaic Cells

The organic photovoltaic cells (OPV) have gained considerable attention because of theirpotential advantages of flexibility, low cost and light-weight etc. It is expected to be one of the newenergy sources of the new generation. The main focus in OPV study is improving the powerconversion efficiency and stability to realize commercial application and benefit human society.In this work, after introducing the brief history, working principle and characterization of OPVdevices, detail studies focusing on small-molecule based OPV devices have been conducted.(1) Employe small ratio of phosphorescent materials as donor component to fabricate organicphotovoltaic (OPV) cells with structure of MoOx/C60: x%phosphor. Firstly, through fabricatingOPV devices with different ratio of Ir(ppy)3, analyze the relationship between the Ir(ppy)3’sconcentration and the open-circuit voltage as well as the short circuit current. In addition, anoptimal device structure was obtained. Device with5%Ir(ppy)3formed the optimal structure withpower conversion efficiency (η) of1.7%. In order to further improve η, C70with more intensive andwide absorption was used to replace the acceptor component of C60. As a result, dramaticallyimproved η (3.0%) was obtained. Then, Ir(BPPya)3、Ir(CzPPya)3fabricated by our own group wereused in the same structure, good device performance was obtained. All these shows phosphor asdonor component is feasible proposal.(2) Use DBP as donor component to fabricate bulky heterojunction (BHJ) OPV cells withstructure of DBP/DBP: x%C60/C60. Through changing the concentration of C60, an optimalstructure with excellent performance was got. Compared this BHJ device with planar heterojunction(PHJ) device based on DBP and C60, the mechanism of OPV devices was explored. Results shows,BHJ structure has better device performance, and in this structure when the C60’s concentration is20%, an optimum structure was got, and the power conversion efficiency is2.5%. It increased a lotcompared with PHJ structure, about25%.