Charting degradation modes and de-risking practical development

Schematic chart filtering the candidate low bandgap compositions

The authors* of the paper 'Charting the irreversible degradation modes of low bandgap Pb-Sn perovskite compositions for de-risking practical industrial development', published in Advanced Energy Materials, identify three irreversible degradation processes when considering the question of which absorber materials for solar technology have the most suitable low bandgap lead-tin composition for all-perovskite tandem applications. 

The identified irreversible degradation processes were identified in narrow bandgap Pb-Sn pervoskite absorbers:

  1. Tin (Sn) oxidation upon air exposure;
  2. methylammonium (MA) loss upon heat exposure; and 
  3. formamidinium (FA) and cesium (Cs) segregation leading to impurity phase formation.

From an industrial perspective, the authors propose refocusing attention on FASn0.5Pb0.5I3, which minimises all three effects while maintaining a suitable bandgap for a bottom cell and good performance.  A practical and highly sensitive characterisation method is also to monitor the oxidation, which can be deployed both in laboratory and industrial environments, and provide useful information for the technological development process, including the effectiveness of encapsulation methods and the acceptable time windows for air exposure. 

 

*the team of authors comprises Oxford Photovoltaics Limited, University of Oxford (Physics), Lancaster University (Chemistry) and Oxford Materials.