AI Article Synopsis
- The study compares organic solar cells with a specific structure, showing that thermal annealing after aluminum deposition leads to better performance than before.
- Ultrafast spectroscopy reveals that postannealing enhances charge transfer and decreases recombination of excited carriers, resulting in improved solar cell efficiency.
- Longer lifetimes of excited carriers in postannealed devices suggest they are more likely to contribute to photocurrent, explaining the performance boost.
Article Abstract
The organic solar cells of heterojunction system, ITO/PEDOT:PSS/P3HT:PCBM/Al, with a thermal annealing after deposition of Al exhibit better performance than those with an annealing process before deposition of Al. In this study, ultrafast time-resolved spectroscopy is employed to reveal the underlying mechanism of annealing effects on the performance of P3HT:PCBM solar cell devices. The analyses of all decomposed relaxation processes show that the postannealed devices exhibit an increase in charge transfer, in the number of separated polarons and a reduction in the amount of recombination between excited carriers. Moreover, the longer lifetime for the excited carriers in postannealed devices indicates it is more likely to be dissociated into photocarriers and result in a larger value for photocurrent, which demonstrates the physical mechanism for increased device performance.
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