From lab to fab: how must the polymer solar cell materials design change? – an industrial perspective

Abstract

Organic photovoltaic (OPV) devices, in particular polymer solar cells, made by solution processed organic materials have shown great promise as a disruptive technology for affordable electricity. Even though recent advances look impressive on paper, until now the commercialization of OPV has been hampered by the difficulty of converting lab produced "champion" cell figures into reliable industrial-scale product performances. A key factor to achieve this condition is to develop OPV materials (polymer donors, acceptors, buffer materials, electrodes materials and encapsulants) exhibiting the required technical and economic characteristics to be conveniently used in an industrial environment. The well established strategies for the design of materials for efficient lab-scale OPV devices are not sufficient when largearea printed panels are concerned. A number of additional requirements, normally not addressed in the laboratory context, must be met: the materials must be easily accessible as pure compounds in few synthetic steps from cheap starting compounds, need to be stable and soluble enough to afford ink formulations processable with roll-to-roll compatible equipment; solvent and solvent additives should be easily removable after printing, and possibly should be environmentally friendly compounds; the layers should achieve a stable morphology under mild conditions (low temperatures and short times); the above mentioned materials can be screened on glass substrates, but should be finally tested on plastic films, protected through a scalable encapsulation technique. The more researchers adhere to these guidelines, the greater the possibility for OPV to demonstrate at last its enormous potential on the industrial scale. Broader contextThe global electric energy demand in 2010 was about 21 400 TW h (source: IEA). Renewable energies accounted for almost one-h of the total energy production. While solar energy was only around 1% of this portion, over the past ve years it has averaged an annual growth rate of over 50%. Growth has been mostly concentrated in a few countries, where PV generates today a few percent of total yearly electricity production. High cost, along with the intermittency of the solar radiation, is one of the main limiting factors, therefore much effort must be spent to overcome these problems. Polymer-based organic solar cells have the potential to be cost-effective and lightweight solar energy converters, with a promising energy balance. Their function is based on the photoinduced electron transfer from a polymeric donor to an acceptor, generally a fullerene derivative. In principle, they can be fabricated by low temperature printing or coating processes from solvent-based inks, which are compatible with exible plastic substrates. Fair power conversion efficiencies ($10%), comparable with amorphous silicon, have been recently achieved in the laboratory, by the combination of improved materials engineering, ne control of the photoactive layer morphology and use of more sophisticated device archit...

Bulk Heterojunction Solar Cells — Opportunities and Challenges

“…Therefore, in real practice the encapsulation of the device is mandatory to guarantee the long-term stability of the device. The water and oxygen transmission properties of the encapsulant materials are thus essential to ensure the stability of the OPV module [29]. The growing concerns over the stability issue on OPV technology and fulfillment of the promise of OPV as a renewable energy technology has initiated the "International Summits on Organic Photovoltaic Stability" (ISOS) [140] to stimulate the research effort to address these issues.…”

“…have ventured into the OPV technology related business, and are struggling to survive in the market. A number of articles have addressed the economic potential of OPV technology to estimate the cost of the OPV electricity [4,[27][28][29][149][150]. One key factor that dominates the cost is definitely the power conversion efficiency.…”

“…Finally we will end up our discussion with a summary and perspective on the future research. There have been many excellent summary works dealing with various aspects of OPV technology, such as the working mechanism and physics of the OPV device [6][7][8][9], design principles and synthesis of new light absorbing materials [9][10][11][12][13][14][15][16][17][18][19], thin film morphology control and characterization [20][21], new device architecture development [22][23][24], interface engineering [25], quantum chemical calculations [26], economical aspects [27][28][29] and many insightful overviews and perspectives [30][31][32][33][34][35][36][37][38][39][40][41][42]. There are also a series of Photovoltaics Literature Survey papers by Santosh Shrestha [43] in Progress in Photovoltaics: Research and Applications which are useful for readers to catch up current research progress in various aspects regarding PV technology.…”

Silver Nanowire Networks as a Transparent Printable Electrode for Organic Photovoltaic Cells

“…[1][2][3][4] Transparent conductive electrodes are an essential element for the OPV cells, and indium tin oxide (ITO) films have been so far dominantly used because of their high transparency toward the solar light and low sheet resistance less than 20 ³ sq…”

Integrated Flexible Conversion Circuit between a Flexible Photovoltaic and Supercapacitors for Powering Wearable Sensors

“…In the flexible electronics literature, multiple publications demonstrated novel energy materials and devices, such as thin-film flexible photovoltaics (PVs) [1][2][3][4][5][6][7][8][9][10] and carbon-based supercapacitors (SCs) [11][12][13][14][15][16][17][18] that are roll-to-roll (R2R) compatible. A few publications have further integrated a PV material with SCs to form an energy device capable of solar energy harvest and storage.…”