4 research outputs found
Efficient Double- And Triple-Junction Nonfullerene Organic Photovoltaics and Design Guidelines for Optimal Cell Performance
The performance of multijunction devices lags behind single-junction organic photovoltaics (OPVs) mainly because of the lack of suitable subcells. Here, we attempt to address this bottleneck and demonstrate efficient nonfullerene-based multijunction OPVs while at the same time highlighting the remaining challenges. We first demonstrate double-junction OPVs with power conversion efficiency (PCE) of 16.5%. Going a step further, we developed triple-junction OPVs with a PCE of 14.9%, the highest value reported to date for this triple-junction cells. Device simulations suggest that improving the front-cell's carrier mobility to >5 × 10-4 cm2 V-1 s-1 is needed to boost the efficiency of double- and triple-junction OPVs. Analysis of the efficiency limit of triple-junction devices predicts that PCE values of close to 26% are possible. To achieve this, however, the optical absorption and charge transport within the subcells would need to be optimized. The work is an important step toward next-generation multijunction OPVs
Pinning Down the Anomalous Light Soaking Effect toward High-Performance and Fast-Response Perovskite Solar Cells: The Ion-Migration-Induced Charge Accumulation
The
light soaking effect (LSE) is widely known in perovskite solar
cells (PVSCs), but its origin is still elusive. In this study, we
show that in common with hysteresis, the LSE is owed to the ion migration
in PVSCs. Driven by the photovoltage, the mobile ions in the perovskite
materials (MA<sup>+</sup>/I<sup>–</sup>) migrate to the selective
contacts, forming a boosted P-i-N junction resulting in enhanced charge
separation. Besides, the mobile ions (MA<sup>+</sup>) can soften and
suture the PCBM/perovskite interface and thus reduce the trap density,
in keeping with a higher open-circuit voltage. Finally, almost LSE-free
PVSCs can be prepared by using 0.1 wt % MAI-doped PCBM as the electron
transport material, whereas overdoping (1 wt % MAI doping) makes the
LSE even more pronounced due to excess mobile ions that need time
to migrate to reach a new quasi-static state