Tin halide perovskite solar cell based on new precursor additive achieves 12.22% efficiency

A group of researchers led by the Chung-Ang University in South Korea has designed a tin halide perovskite (Sn-HP) solar cell that utilizes an additive known as 4-Phenylthiosemicarbazide (4PTSC) to reduce imperfections in the perovskite layer.

“The use of wide bandgap tin halide perovskites (Sn-HP) offers an eco-friendly option for multi-junction Sn-HP photovoltaics,” research co-author, Padmini Pandey, told pv magazine. “However, rapid crystallization often results in poor film morphology and substantial defect states, hampering device efficiency. Our investigation introduces a novel multifunctional additive to tackle these issues.”

According to the research team, 4PTSC enhances solution stability and delays perovskite crystallization through Lewis acid-base adduct formation, yielding defect-free films with preferential crystal growth. “We chose a multifunctional molecule that acts as both a coordination complex and a reducing agent, passivates defect formation, and improves stability,” Pandey added.

The 4PTSC additive is reportedly able to curb the insurgence of defect states through chemical interactions with uncoordinated Sn ions. This, in turn, is said to halt Sn oxidation and reduce non-radiative recombination, thus also enhancing carrier lifetime and extraction.

The academics designed the cell with an indium tin oxide (ITO) substrate, a hole transport layer made of PEDOT:PSS, the perovskite absorber, an electron acceptor made of phenyl-C61-butyric acid methyl ester (PCBM), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.

Tested under standard illumination conditions, the cell achieved a maximum power conversion efficiency of 12.22% and a certified efficiency of 11.70%.

“The additive significantly boosts the open-circuit voltage to 0.94V and realizes a record highest efficiency for the champion device, low open-circuit voltage loss, and negligible hysteresis in the wide-bandgap Sn perovskite solar cell,” Pandey stated. “Additionally, 4PTSC-1.0 devices show exceptional stability over 1,200 hours in ambient without encapsulation.”

According to the group, chemical coordination between 4PTSC and SnI2 shields the perovskite surface, and passivates uncoordinated Sn2+ and halide ions, suppressing deep trap state formation. “NH2 nucleophilic sites in 4PTSC hinder SnI2 oxidation and ion migration, while its π-conjugated phenyl ring promotes crystal growth orientation and stability,” Pandey further explained. “These multifunctional attributes collectively enhance device efficiency by suppressing non-radiative defect formation.”

The scientists presented their findings in the paper “4-Phenylthiosemicarbazide Molecular Additive Engineering for Wide-Bandgap Sn Halide Perovskite Solar Cells with a Record Efficiency Over 12.2%,” published in Advanced Energy Materials.