5 years ago

Efficiency Exceeding 11% in Tandem Polymer Solar Cells Employing High Open-Circuit Voltage Wide-Bandgap π-Conjugated Polymers

Efficiency Exceeding 11% in Tandem Polymer Solar Cells Employing High Open-Circuit Voltage Wide-Bandgap π-Conjugated Polymers
Kakaraparthi Kranthiraja, Jin Young Kim, Bright Walker, Taehyo Kim, Jungwoo Heo, Sung-Ho Jin, Seyeong Song
The emerging field of tandem polymer solar cells (TPSCs) enables a feasible approach to deal with the fundamental losses associated with single-junction polymer solar cells (PSCs) and provides the opportunity to propel their overall performance. Additionally, the rational selection of appropriate subcell photoactive polymers with complementary absorption profiles and optimal thicknesses to achieve balanced photocurrent generation are very important issues which must be addressed in order to realize paramount device performance. Here, two side chain fluorinated wide-bandgap π-conjugated polymers P1 (2F) and P2 (4F) in TPSCs have been used. These π-conjugated polymers have high absorption coefficients and deep highest occupied molecular orbitals which lead to high open-circuit voltages (Voc) of 0.91 and 1.00 V, respectively. Using these π-conjugated polymers, TPSCs have been successfully fabricated by combining P1 or P2 as front cells with PTB7-Th as back cells. The optimized TPSCs deliver outstanding power conversion efficiencies of 11.42 and 10.05%, with high Voc's of 1.64 and 1.72 V, respectively. These results are analyzed by balance of charge mobilities, and optical and electrical modeling is combined to demonstrate simultaneous improvement in all photovoltaic parameters in TPSCs. High performance of tandem polymer solar cells (TPSCs) with power conversion efficiencies (PCEs) up to 11.42 and 10.05% are realized by using fluorine-functionalized polymers. TPSCs with PCEs over 10% achieved open-circuit voltage (Voc) of up to 1.72 V, which is among the highest Voc observed in TPSCs to date. Furthermore, detailed analyses of TPSCs as well as guidelines for bottom cell design are demonstrated.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700782

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