In an attempt to increase the efficiency of organic solar cells, a team of Stanford researchers has recently discovered how “tuning” quantum dot solar cells (also recently invented) with an organic layer can triple its efficiency.
While studying quantum dot solar cells, chemical engineering Professor Stacey Bent and associate Professor Michael McGehee of the department of Materials Science and Engineering coated a titanium dioxide semiconductor in their quantum dot solar cell with a very thin single layer of self-assembling organic molecules.
Solar cells use the energy from the sun to excite electrons, who jump from a lower energy level to a higher one, leaving behind a “hole” where the electron used to be. A semiconductor is used to pull an electron in one direction, and another material to pull the hole in the other direction. This flow of electron and hole in different directions leads to an electric current.
Bent theorized that once the sun’s light, through photons, creates an electron and a hole, the thin organic layer helps keep them apart, preventing them from recombining and being wasted. She and her team experimented with the newly-developed cell prototype and concluded that the nanometer-thick organic material is not important in itself, but rather its molecule sizes. “We were surprised, we thought it would be very sensitive to what we put down,” said Bent.
They still have to optimize the solar cells, having currently achieved an efficiency of only 0.4 percent – at most – in their preliminary tests. Results have been published in ACS Nano, in the Feb. 7 issue.
Prof. Bent had been involved in the research of artificial eye implants in 2003.