Design optimization & fabrication of 3″ₓ3″ flexible polymer solar modules

Organic solar cells based on conducting polymers have great potential towards portable electronics owing to their light weight, flexibility, scalability, solution processability, etc. Indium tin oxide (ITO) coated PET substrates act as the base conducting substrate for typically all flexible solar cells, and this accounts for 50-60% of the cost. Therefore, a cheaper ITO-free approach needs to be explored. In this work, we present our in-house fabricated PEDOT based transparent/conductive flexible substrates, which demonstrate transparencies >90% and conductivities > 3000 S/cm. The substrates were characterized using Raman, AFM, XPS, and UV-Vis spectroscopy. The initial results with small cells fabricated using these substrates showed promising results. Therefore, these substrates were used as the base conducting substrates for flexible polymer modules in place of ITO/PET substrates. Large area polymer solar modules have been fabricated with the device structure PET/HC-PEDOT:PSS/Active Layer/Al. The typical modules have 27 devices (each device has ~ 0.1cm² area) in series on a single substrate (3″^ₓ3″), which exhibited ~15V and ~0.3 mA, under 1Sun illumination.