Hybrid organic–inorganic methylammonium lead halide perovskites have attracted intense attention for thin-film photovoltaics, due to their large absorption coefficient, high charge carrier mobility and long diffusion length. However, these cells are also costly because of the hole-transportation layer, which demands high purity materials and complicated fabrication procedures.
A team of scientists at the Michael Grätzel Center for Mesoscopic Cells of Huazhong University in China in cooperation with the Laboratory for Photonics and Interfaces at EPFL directed by Michael Grätzel have successfully manufactured a perovskite solar cell that does not need a hole-transportation layer. The solar cell shows comparative energy conversion efficiency (12.8%) and was shown to be stable for over 1000 hours in direct sun exposure.
The scientists fabricated the new solar cell by drop-casting a solution of lead iodide, methylammonium iodide, and 5-ammoniumvaleric acid iodide through a porous carbon film. The solar cell’s scaffolding was made using a double layer of titanium dioxide and zirconium dioxide covered by a porous carbon film and amino acid templating agent was used to promote the pervoskite nucleation and crystal growth within the pores . The resulting perovskite crystals showed much higher electrical charge generation and collection efficiency than conventional hole conductor free perovskite cells. The use of organic-hole conductor free triple layer also resulted in strikingly high stability.
Perovskite solar cells are ideally placed to meet the increasing demands for renewable energy in the future. This breakthrough innovation addresses one of their major limiting factors, and paves the way for a new, cost-effective branch of development in this type of solar cell.
This work represents a collaboration between EPFL’s Laboratory of Photonics And Interfaces and the Michael Grätzel Center for Mesoscopic Cells of Huazhong University of Science and Technology (China).
Image credit: EPFL