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Effect of Molecular Orientation of Donor Polymers on Charge Generation and Photovoltaic Properties in Bulk Heterojunction All‐Polymer Solar Cells
Author(s) -
Jo Jea Woong,
Jung Jae Woong,
Ahn Hyungju,
Ko Min Jae,
Jen Alex K.Y.,
Son Hae Jung
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.201601365
Subject(s) - materials science , polymer solar cell , acceptor , polymer , electron donor , crystallinity , electron acceptor , solar cell , photochemistry , chemical engineering , optoelectronics , organic chemistry , chemistry , composite material , physics , engineering , condensed matter physics , catalysis
All‐polymer solar cells (all‐PSCs) utilizing p ‐type polymers as electron‐donors and n ‐typepolymers as electron‐acceptors have attracted a great deal of attention, and their efficiencies have been improved considerably. Here, five polymer donors with different molecular orientations are synthesized by random copolymerization of 5‐fluoro‐2,1,3‐benzothiadiazole with different relative amounts of 2,2′‐bithiophene (2T) and dithieno[3,2‐ b ;2′,3′‐ d ]thiophene (DTT). Solar cells are prepared by blending the polymer donors with a naphthalene diimide‐based polymer acceptor (PNDI) or a [6,6]‐phenyl C 71 ‐butyric acid methyl ester (PC 71 BM) acceptor and their morphologies and crystallinity as well as optoelectronic, charge‐transport and photovoltaic properties are studied. Interestingly, charge generation in the solar cells is found to show higher dependence on the crystal orientation of the donor polymer for the PNDI‐based all‐PSCs than for the conventional PC 71 BM‐based PSCs. As the population of face‐on‐oriented crystallites of the donor increased in PNDI‐based PSC, the short‐circuit current density ( J SC ) and external quantum efficiency of the devices are found to significantly improve. Consequently, device efficiency was enhanced of all‐PSC from 3.11% to 6.01%. The study reveals that producing the same crystal orientation between the polymer donor and acceptor (face‐on/face‐on) is important in all‐PSCs because they provide efficient charge transfer at the donor/acceptor interface.