A variety of solar energy conversion systems have emerged as attractive candidates to establish fossil fuel-free energy networks.[1-3] Among these, organic solar cells offer the promise of lightweight, flexible, large-area, and cost-effective photovoltaic technology. Traditionally, organic photovoltaic devices (OPVs) have been fabricated with thermal evaporation or solution-based techniques, but these two methods are suitable for only low molecular weight or soluble materials. In order to apply high molecular weight and insoluble polymers to OPVs, we explore the use of oxidative vapor deposition (oCVD) for the polymer deposition.
As shown in Figure 1, oCVD is a solvent-free conformal vacuum-based technique to enable thin-film fabrication of insoluble polymers at moderate vacuum (~ 0.1 Torr) and low temperature (25 – 150 °C). Moreover, oCVD carries the well-cited processing benefits of vacuum processing, such as parallel and sequential deposition, well-defined thickness control, large-area uniformity, and inline integration with other standard vacuum processes (e.g. vacuum thermal evaporation).[1,4,6]
Based on the abovementioned technical advantages from oCVD, various insoluble polymers are successfully applied to OPVs. First, polyselenophene donor layers are integrated into OPVs for the first time with 0.4 % of power conversion efficiency (Figure 2). Second, ternary OPVs employing polythiophene donor layers has been realized to increase the power conversion efficiency up to 2.4% (Figure 3). Third, a new concept of neutral hole transporting layers (HTLs) is achieved by integrating patterned Cl− doped poly(3,4-dimethoxy-thiophene) (PDMT) HTLs into OPVs via oCVD. Due to this novel polymer’s neutrality, high transparency, good conductivity, and appropriate energy levels, the power conversion efficiency and lifetime of OPVs are remarkably boosted compared to those of OPVs depending on the commercial hole transporting polymer, acidic PEDOT:PSS [poly(3,4-ethylenedioxy-thiophene):polystyrene sulfonate] (Figure 4). Finally, we are currently studying hyper-conductive PEDOT for printable and flexible electronics by using a vacuum-based polymer vapor printing technique – oxidative chemical vapor deposition (oCVD) combined with in-situ shadow masking.
 W. J. Jo, D. C. Borrelli, V. Bulovi?, K. K. Gleason, Org. Electron. 2015, 26, 55.
 W. J. Jo, J.-W. Jang, K. Kong, H. J. Kang, J. Y. Kim, H. Jun, K. P. S. Parmar, J. S. Lee, Angew. Chem. Int. Ed. 2012, 51, 3147.
 W. J. Jo, H. J. kang, K. Kong, Y. S. Lee, H. Park, Y. Lee, T. Buonassisi, K. K. Gleason, J. S. Lee, Proc. Natl. Acad. Sci. U.S.A. 2015, 112, 13774.
 A. M. Coclite, R. M. Howden, D. C. Borrelli, C. D. Petruczok, R. Yang, J. L. Yagüe, A. Ugur, N. Chen, S. Lee, W. J. Jo, A. Liu, X. Wang, K. K.Gleason, Adv. Mater. 2013, 25, 5392.
 W. J. Jo, D. C. Borrelli, V. Bulovi?, K. K. Gleason, to be submitted.
 W. J. Jo, J. T. Nelson, V. Bulovi?, M. S. Strano, K. K. Gleason, Adv. Mater. under minor revision.
 W. J. Jo, K. K. Gleason, in preparation.
|Category||Short file description||File description||File Size|
|Manuskript||Figure 1||oCVD reactor scheme||64 KB||Download|
|Manuskript||Figure 2||Polyselenophene solar cells' architecture||43 KB||Download|
|Manuskript||Figure 3||Energy level alignment of polythiophene, DBP, C60||21 KB||Download|