ZnO nanoparticles modified with biomaterial GHK-Cu as electron transport layer to fabricate highly efficient inverted polymer solar cells

Abstract

The interfacial modification with biomaterials is an effective and environmental protection way to improve the efficiency of inverted polymer solar cells (IPSCs) by reducing the defects and interface recombination of ZnO electron transport layer (ETL). In this paper, ZnO surface is successfully modified via Gly-His-Lys-Cu (GHK-Cu), a nontoxic biomaterial, to fabricate novel ZnO&GHK-Cu composite film. The modification of ZnO surface by GHK-Cu makes the Zn-O-Cu bond formed on the surface of ZnO, which provides a channel for the electron transfer from electron-rich functional groups (such as carboxyl, amino and carbonyl) to Zn2+, the electron defects caused by the oxygen vacancies in the ZnO lattice are passivated, which is beneficial to the transfer and extraction of charges in IPSCs. Moreover, the modification of GHK-Cu decreases the chemisorbed oxygen of the surface of ZnO, the height of the Schottky barrier between the ZnO crystal grains is reduced, resulting in an increase in the conductivity of ZnO. The novel ZnO&GHK-Cu composite film has excellent photoelectric properties and IPSCs with new ZnO&GHK-Cu as ETL are fabricated for the first time. As the result, the IPSCs based on PBDB-T:ITIC with ZnO&GHK-Cu as ETL show an optimal power conversion efficiency (PCE) of 11.93%, increases by 15.6% in comparison with ZnO ETL-based IPSCs with a PCE of 10.32%. Meanwhile, the PCE of IPSCs based on PM6:Y6 increases from 14.66% to 16.46%. More interesting, the physical mechanism of improving the performance of IPSCs by modifying of ZnO surface with biomaterial has been deeply analyzed. The work provides an effective method for modification of ZnO surface, also shows that biomaterial GHK-Cu has application prospect in photovoltaic devices.