Holon Physics Seminar

 

The greatest challenge facing the development of low-cost, solution processed photovoltaic (PV) devices, namely organic- and perovskite- based solar cells, is combining high efficiency, processability and stability. While inorganic solar cells exhibit operational lifetimes in the range of 25 years, the operational lifetime of organic devices only recently reached a few years, and is yet to be determined for perovskite solar cells. Concentrated natural sunlight was suggested for accelerated studies of lifetime and light-induced degradation.

 

We demonstrated an experimental methodology with independent control of sunlight intensity, the sample temperature and environment during the exposure. P3HT:PCBM films revealed stability for the equivalent of 1.5 years, a result obtained within merely two measurements days. PTB7:PCBM showed solvent-dependent structure and degradation. Studies of perovskite PV materials showed a strong dependence of the stability on the materials composition, correlated with chemical bond strength and crystalline structures.

 

The stability of pure MAPbI3 and MAPbBr3 films was found to be superior to that of mixed halide compositions MAPb(I1-xBrx)3, possibly due to internal strain in the deformed crystal of the solid solution. The results of accelerated stability testing of these materials were correlated with stability testing under regular operation conditions, i.e., 1-sun exposure. Accelerated testing using concentrated sunlight is therefore a powerful tool for material and device screening and advanced PV development.