Upscaling of polymer solar cells

This report investigates the potential and challenges for all-polymer solar cells to be produced using scalable coating processes. Three systems are studied, two all-polymer blends (J52:N2200 and J71:PNDI-T10) and a novel polymer non-fullerene acceptor (NFA) system (PTQ10:ITIC-Br). The effect of increasing cell area from 0.045 cm² to 1.0 cm² for active layers prepared via spin-coating is first investigated. Decreases in efficiency are seen which are attributed to increased series resistance. Smaller cells are also found to benefit from “edge-effects” where carriers generated outside the nominal active area are collected. For spin-coated cells, efficiencies of ~6% for J52:N2200 cells, ~5% for J71:PNDI-T10 cells and ~ 9% for PTQ10:ITIC-Br cells are achieved. J52:N2200 and PTQ10:ITIC-Br cells produced by blade-coating, a scalable coating process, are described. For the J52:N2200 system a ~5% power conversion efficiency is achieved for 1.0 cm2 blade coated cells while an efficiency of ~9% could be maintained for 1.0 cm² blade-coated PTQ10:ITIC-Br cells. For all-polymer solar cells, leakage current was found to decrease with active area for spin-coated cells, but increased with active area for blade-coated cells. For the polymer/NFA system studied leakage current was found to increase with active area for both spin-coated and blade-coated cells. Our findings demonstrate the potential for these systems to be coated at scale. Strategies to mitigate series resistance and improve the uniformity of blade-coated layers will help boost the efficiency of large area, scalably coated cells.