Performance Analysis of Printed Bulk Heterojunction Solar Cells

• Published in: Advanced functional materials 2006-09, Vol.16 (13), p.1669-1672
• Main Authors: Schilinsky, P., Waldauf, C., Brabec, C. J.
• Format: Article
• Language: English
• Subjects: Fullerenes; Heterojunctions; Polythiophenes; Solar cells
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200500581

In this paper we report on printed bulk heterojunction solar cells from poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) with power efficiencies of over 4 %. Devices have been produced by doctor blading, which is a reel‐to‐reel compatible large‐area coating technique. Devices exhibit a short‐circuit current of over 11.5 mA cm–2, a fill factor of 58 %, and an open‐circuit voltage of 615 mV, resulting in an AM1.5 power efficiency of over 4.0 % at 25 °C and under 100 mW cm–2. The mismatch factor of the solar simulator is cross‐calibrated by determining the spectral quantum efficiency of organic devices as well as of a calibrated Si device, and by the combination of outdoor tests; these efficiencies are precise within less than 3 % relative variation. Although the devices are regarded as fairly optimized, analysis in terms of a one‐diode equivalent circuit reveals residual losses and loss mechanisms. Most interestingly, the analysis points out the different properties of spin‐coated versus bladed devices. Based on this analysis, the future efficiency potential of P3HT–PCBM solar cells is analyzed. Printed bulk heterojunction solar cells from poly(3‐hexylthiophene) and a methanofullerene with power efficiencies of over 4 % are reported (see figure). Though these devices appear fairly optimized, analysis on the basis of a one‐diode equivalent circuit reveals residual open‐circuit voltage losses as well as fill‐factor losses. Imperfections in the bulk distribution of the nanometer‐scaled donor–acceptor heterojunctions are suggested as the origin for the residual losses.