Although the current photovoltaic market (PV) is dominated mainly by crystalline silicon devices which control 85% of the PV market, there has been a new wave of technologies entering the market which include organic photovoltaics (OPV). Photovoltaic devices based on organic polymers and small molecules are an emerging technology and have great potential for low cost and scalable renewable energy harvesting. The global organic solar cell market was worth $25 million in 2013. However measured in terms of efficiency and cost in dollars/watt, they still underperform and are overpriced. Thus far, the most successful organic photovoltaic is in the form of polymer/fullerene bulk heterojunctions with up to ~7% power conversion efficiency. Charge recombination and the low carrier mobility of polymer limits overall power conversion efficiency thus making it commercially less viable. With the market of OPV expected to reach $97 million in 2020, growing at a CAGR of 21.2% from 2014 to 2020, there is substantial opportunity to develop OPV to become a competitive player in the renewable energy business landscape.
Efficient photocurrent generation with carbon nanotube/ P3HT hybrid structure for next generation organic photovoltaics.
A generic organic photovoltaic device consists of a donor-acceptor system, enabling exciton dissociation and charge separation at the heterojunction. The interpenetrated donor-acceptor network within a bulk heterojunction photovoltaic maximizes the exciton dissociation efficiency but they also slow down the charge extraction resulting in low photocurrent essentially due to low carrier mobility. As a solution, single-walled carbon nanotubes (SWNTs) are among the top candidates with orders of magnitude higher carrier mobilities than conducting polymers. Researchers at University of Michigan have developed a new technology for efficient photocurrent generation in single-walled carbon nanotubes (SWNTs)/poly [3-hexylthiophene-2,5-diyl] (P3HT) hybrid photovoltaics. Photocurrent measurement at individual SWNT/P3HT heterojunctions have revealed that both semiconducting (s-) and metallic (m-) SWNTs function as excellent hole acceptors. Electrical transport and gate voltage dependent photocurrent studies confirm that P3HT p-dopes both s-SWNT and m-SWNT, and exciton dissociation is driven by a built-in voltage at the heterojunction leading to 90% internal quantum efficiency. These key features of the invention will lead to carbon nanomaterial based low cost high efficiency hybrid photovoltaics.
- Solar cell
- Renewable energy
- Flexible and light-weight leading to wide variety of use
- Low cost manufacturing