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Efficiency Exceeding 11% in Tandem Polymer Solar Cells Employing High Open‐Circuit Voltage Wide‐Bandgap π‐Conjugated Polymers
Author(s) -
Song Seyeong,
Kranthiraja Kakaraparthi,
Heo Jungwoo,
Kim Taehyo,
Walker Bright,
Jin SungHo,
Kim Jin Young
Publication year - 2017
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201700782
Subject(s) - materials science , tandem , polymer , photocurrent , conjugated system , band gap , optoelectronics , open circuit voltage , polymer solar cell , energy conversion efficiency , photovoltaic system , absorption (acoustics) , voltage , electrical engineering , composite material , engineering
Abstract 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 ( V oc ) 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 V oc '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.