Increasing the efficiency of a multilayer bulk heterojunction solar cell using water-soluble conjugated polymer as an electron injection layer

Abstract

A bulk heterojunction solar cell (BHJ-SC) was fabricated from the conventional active polymer blend P3HT:PCBM by constructing a polymer multilayer structure with novel electron-transporting water-soluble conjugated polymers (WSCPs), poly[9,9′-bis[2-(2-(2-(6′′-(N,N,N-trimethylammonium) ethoxy) ethoxy) ethoxy) ethyl]fluorine, and its copolymer with a phenyl on top of the polymer active layer. In the multilayer structure BHJ-SC, each WSCP coordinated by Na+ ions to the oxygen site on the side chain of the polymer acts as a good electron injection layer for the higher electron collection at the cathode metal. This causes up to 85% increase in the BHJ-SC's power conversion efficiency (PCE) compared to that of the BHJ-SC without WSCPs. This report will discuss the effect of the electron injection layer in the BHJ-SC in terms of the current/voltage characteristics, PCE, electron affinity, and charge mobility of water-soluble polymers.