Solar Panels
Perovskite solar cells show tremendous promise in propelling solar power into the marketplace. The latest research helps reduce the cost of manufacture of these while increasing the efficiency.REUTERS

Scientists have made a very efficient perovskite solar cell that reduces the cost of manufacture and increases energy conversion efficiency of the wonder material which holds tremendous promise in propelling solar power into the marketplace.

The photovoltaic cell achieved energy conversion efficiency of 12.8% and was stable for over 1000 hours under full sunlight.

Publishing in Science, a team of scientists in China, led by Professor Hongwei Han in cooperation with Professor Michael Grätzel at EPFL, have developed a perovskite solar cell that does away with the need for a hole-transporting layer. Besides the above-mentioned attributes, the resulting perovskite crystals also showed strikingly high stability.

These solar cells have been strong contenders for thin-film photovoltaics due to their large absorption coefficient, high charge carrier mobility and long diffusion length. However, they are also costly because of the hole-transportation layer, which demands high purity materials and complicated fabrication procedures.

Solar cell manufacturers face a tricky trade-off between performance and cost. Most commercial solar cells rely on slabs of crystalline silicon that are more than 150 micrometers thick and take a lot of energy to produce. Despite the high efficiency of conventional crystalline silicon solar cells (around 20%), high production and installation costs decrease their economic feasibility and widespread use.

Thin-film solar cells have lower material costs, but they are also less efficient. Cells using crystalline gallium arsenide, on the other hand, can reach 30%, but the materials involved are too costly for utility-scale solar power.

The challenge to find a cheaper alternative led to the development of perovskite-based solar cells, as organic–inorganic metal trihalide perovskites have both abundant and cheap starting materials. The rapid rise of perovskites is unprecedented in solar photovoltaic research, where efficiencies usually inch upward over decades.

Researchers are convinced that there is still plenty of room for improvement, predicting that perovskite cells will surpass 20% efficiency by the end of the year.

At a Materials Research Society meeting in April, materials scientist Yang Yang at the University of California, Los Angeles, had developed a 19.3%-efficient perovskite cell — good enough to rival some commercial crystalline silicon solar cells with 17-23% efficiency.

Already exhibiting conversion efficiencies of over 16%, organic-inorganic lead halide perovskite solar cells are one of the most promising emerging contenders in the drive to provide a cheap and clean source of energy. But the presence of lead has led to environmental concerns. The most likely substitute is tin.