Browsing by Author "Meng, Lei"

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Efficient Tandem Organic Photovoltaics with Tunable Rear Sub-cells
(2019-02-20)
Cheng, Pei
;
Liu, Yuqiang
;
Chang, Sheng-Yung
;
Li, Tengfei
;
Sun, Pengyu
A tandem structure was invented to enhance photon utilization efficiency and reduce thermal loss. Considering the unique advantages of non-fullerene acceptors (NFAs), the combination of NFAs and the tandem concept shows great potential for organic photovoltaics (OPVs). Herein, a simple strategy to balance the voltage-current trade-off in tandem OPVs by employing mixed NFAs in rear sub-cells is reported. The V-OC and J(SC) of rear sub-cells can be tuned by using the blend of donor/NFA/NFA. This strategy offers an easy approach to balance the V-OC and J(SC) in tandem OPVs toward higher power conversion efficiency (PCE) without rational and careful synthesis of new materials. Tandem OPVs based on mixed NFAs in rear sub-cells exhibited the best PCE of 13.3% in the lab. Importantly, the tandem devices were certified by the National Renewable Energy Laboratory (NREL) under asymptotic scans, and a PCE of 11.52% was achieved and recognized on the most recent NREL chart.
High-Efficiency Organic Tandem Solar Cells With Effective Transition Metal Chelates Interconnecting Layer
(2017-10-01)
Chang, Sheng-Yung
;
Lin, Yu-Che
;
Sun, Pengyu
;
Hsieh, Yao-Tsung
;
Meng, Lei
Organic tandem solar cells have two sub-cells vertically connected via a tunnel junction (or interconnecting layer, ICL), which the ICL plays a critical role of determining the performance of the tandem cell. In this manuscript, we report a new design of the ICL consisting of zirconium (IV) acetylacetonate (Zr-Acac) as the electron transport layer. The Zr-Acac has a suitable work function to pin the Fermi-level of the ICL and hence, can effectively behave as the charge recombination function for the tandem device. Comparing to the reference device consisting of ZnO ETL layer, the Zr-Acac ICL can effectively enhance the efficiency by 20%, from 8.4 to 10.1% power conversion efficiencies. More importantly, the Zr-Acac ETL layer functions effectively without thermal annealing, which not only simplifies the tandem solar cell processing, but also widens the front sub-cell material selection.