Perovskite solar cells achieve 22.3% power conversion efficiency with salt use
Researchers have revealed that a type of salt can improve the efficiency of perovskite solar cells. Called guanidinium thiocyanate, the salt boosts perovskite solar cells’ power conversion efficiency and their stability.
The approach could make solar power cheaper and more powerful.
Researchers at the University College London revealed that guanidinium thiocyanate can slow and control the way perovskite crystals form during fabrication, creating smoother and more uniform layers.
This helps reduce the tiny flaws in the material that can hinder performance and shorten a cell’s lifespan.
Effective way to enhance perovskite quality
“Our approach provides a straightforward, effective way to enhance perovskite quality during manufacturing, delivering solar cells that are both higher performing and more stable, key requirements for commercial success,” said corresponding author Dr Tom Macdonald (UCL Electronic & Electrical Engineering).
The research team revealed that during experiments, the material achieved an efficiency of 22.3%, close to the best reported for mixed tin-lead perovskites.
For comparison, the best silicon solar cells in the lab have reached around 27% efficiency, while most commercial panels installed on rooftops today deliver about 22%. All-perovskite tandem devices (that is, using more than one layer of perovskite cell) have already surpassed 30% in the lab, highlighting their potential to achieve a step-change in solar power generation, according to a press release.
Using salt for the bottom layer of tandem cells
The team stressed that using salt for the bottom layer of tandem cells – either guanidinium thiocyanate or potentially another agent – would likely increase this world-record efficiency further.
“This work gave us valuable insight into the crystal formation process. By modulating it in a controlled way, we were able to create much higher-quality films – a change that directly translates into more efficient and longer-lasting devices,” said first author Yueyao Dong (UCL Electronic & Electrical Engineering).
The research team highlighted that the method opens the door to fine-tuning the structure of perovskites for high-performance tandem solar cells, with the potential to significantly push the limits of efficiency.
Optoelectronic properties of various perovskite compositions enhanced
The incorporation of guanidinium (Gua) cations has significantly enhanced the optoelectronic properties of various perovskite compositions. When combined with other A-site cations in perovskite solar cells (PSCs), Gua cations not only enhance the power conversion efficiency of the solar cells but also often improve their overall stability.
While most studies examining the impact of Gua focus on PSCs with the n-i-p (conventional) structure, fewer have investigated its effects on the mechanism and performance of the p-i-n (inverted) structure.
“We investigate how partially substituting A-site cations with Gua affects the performance of PSCs and the associated charge carrier dynamics. Enhanced performance is observed in Gua-substituted inverted PSCs, primarily due to improved short-circuit current density and fill factor values,” described researchers in the study published in ACS Energy Letters.