All-plastic solar cells with a high photovoltaic dynamic range† Yinhua Zhou, Talha M. Khan, Jae Won Shim, Amir Dindar, Canek Fuentes-Hernandez and Bernard Kippelen * We report on semitransparent air-processed all-plastic solar cells, fabricated from vacuum-free processes, comprising two polymer electrodes, a polymeric work-function modification layer and a polymer:fullerene photoactive layer. The active layer and the top PEDOT:PSS electrode were prepared by sequential film- transfer lamination on polyethylenimine-modified PEDOT:PSS bottom electrodes. The transferring of films offers ease of layer patterning and the misalignment of defects in the different layers resulting from the additive film transfer lamination process yields high shunt resistance values of 10 8 ohm cm 2 . Consequently, all-plastic solar cells fabricated with this process exhibit very low reverse bias dark current and can operate in the photovoltaic quadrant with light irradiance varying over five orders of magnitude. The analysis of the values of the open-circuit voltage as a function of light irradiance over that wide dynamic range points toward an ideality factor of n ¼ 1.82 and a reverse saturation current density of 6.2  10 11 A cm 2 for solar cells with an active layer comprised of a blend of poly(3-hexylthiophene) and an indene fullerene bis-adduct. Organic solar cells are attractive because of their potential for low cost fabrication, light weight, and excellent mechanical exibility. 1–10 Currently, most common organic solar cells are fabricated on indium tin oxide (ITO) coated glass substrates with vacuum-deposited evaporated metals used as the top electrodes. To realize the full potential for low cost, ITO-free organic solar cells should preferably be fabricated using vacuum-free processes in ambient air. 11–13 Recently, we reported all-plastic solar cells comprising polymer electrodes: poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and active layer: poly(3-hexylthiophene) (P3HT):indene-C 60 bis- adduct (ICBA). 1 These all-plastic solar cells were fully processed in air from solutions of orthogonal solvents using spin coating. In these devices, the solvent used to process the active layer, typically chlorobenzene or dichlorobenzene, allows for water- based solutions of the conducting polymer PEDOT:PSS to be deposited on top with minimum damage of the layer under- neath but wetting issues can be a challenge. Film-transfer lamination is a method of lm preparation wherein a lm is rst deposited on a carrier substrate (typically crosslinked polydimethylsiloxane, PDMS), and is then lami- nated onto the target substrate with the carrier substrate. The carrier is nally peeled away to nish the lm transfer. Transfer lamination is a dry process and avoids wetting issues and lm damage arising from the use of non-orthogonal solvents during spin coating, ink-jet printing or any other additive wet-deposi- tion method. The lm-transfer lamination technology has been used to prepare top metal electrodes, 14 PEDOT:PSS 15,16 and active layers 17,18 in organic light-emitting diodes and organic solar cells. Because of the solvent-free dry process used during the transfer lamination, this technique was used to construct multi-layer organic lms as the active layer. 19–21 It was also used to modulate the vertical phase segregation in P3HT:ICBA to study its effect on solar cell performance. 22,23 Another important advantage of the lm-transfer lamination technique is the ease in patterning the top PEDOT:PSS electrode as compared to the spin coating technique. In this work, we report on the rst demonstration of semi- transparent all-plastic solar cells fabricated in ambient air by sequential dry lm-transfer lamination of a P3HT:ICBA photo- active layer and a PEDOT:PSS (high conductivity formulation, PH1000) top electrode. Fig. 1a shows the device structure of the solar cells. The bottom electrode is comprised of a patterned PH1000 lm, modied by a thin layer of polyethylenimine (PEI). PEI modication has been proven to improve the electron collection and performance of various types of solar cells by signicantly reducing the work function of the underlying conductor. 1,24–30 The P3HT:ICBA and PH1000 lms are respec- tively used as the active layer and the top electrode, and are prepared by lm-transfer lamination. These layers are hereby referred to as P3HT:ICBA-L and PH1000-L. Fig. 1b illustrates the procedure for fabrication of the all-plastic solar cells. This Center for Organic Photonics and Electronics (COPE), School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. E-mail: kippelen@ece.gatech.edu † Electronic supplementary information (ESI) available. See DOI: 10.1039/c3ta15073a Cite this: J. Mater. Chem. A, 2014, 2, 3492 Received 6th December 2013 Accepted 17th January 2014 DOI: 10.1039/c3ta15073a www.rsc.org/MaterialsA 3492 | J. Mater. Chem. A, 2014, 2, 3492–3497 This journal is © The Royal Society of Chemistry 2014 Journal of Materials Chemistry A PAPER