8.26% efficiency boost in eco-friendly solar cells achieved, advancing commercialization prospects

A research team has developed a technology that can significantly increase the efficiency of eco-friendly solar cells. The solar cells they developed showed increased power conversion efficiency of up to 8.26%, compared with conventional solar cells. This finding is expected to accelerate the commercialization of next-generation eco-friendly solar cells.

The research is published in the journal Advanced Energy Materials.

Silver bismuth sulfide (AgBiS₂) nanocrystals have recently attracted attention as an eco-friendly solar cell material. Existing high-efficiency solar cells contain harmful heavy metals such as lead and cadmium, causing environmental pollution, but silver bismuth sulfide has the advantage of being non-toxic and abundant in raw materials. However, its limitation is that when it exceeds a certain thickness, electricity does not flow well, causing a sharp drop in efficiency.

To solve this problem, the research team developed a thin film with a special mixed structure to allow electricity to flow better. In other words, they mixed materials to create a layer that improves the flow of electricity. The team chemically treated silver bismuth sulfide nanocrystals to give different properties (donor and acceptor) to one layer, allowing electricity to move more efficiently inside.

As a result, when they made a 65 nm (nanometer) light-absorbing layer twice as thick as the conventional ones, its performance was maintained and the efficiency of the solar cell was improved by 8.26%. This is equivalent to charging a smartphone four to five times or keeping an LED light bulb on for over two hours longer.

“This research has greatly increased the charge diffusion length by allowing the donor and acceptor to coexist in the same layer of the AgBiS₂ solar cell, thus maintaining performance even in thicker layers,” said Prof. Choi Jong-min of DGIST’s Department of Energy Science and Engineering. “We expect this eco-friendly technology to be applied to various high-efficiency solar cells in the future.”

This joint research between DGIST Prof. Choi’s team and UNIST Prof. Kwon Oh-hoon’s team was led by DGIST Energy Science and Engineering students Kim Hae-jung and Park Jin-young, and UNIST combined Master’s and doctoral program student Choi Ye-jin.