Development of Polymer Blend Solar Cells Composed of Conjugated Donor and Acceptor Polymers

Abstract

All-polymer solar cells are expected as one of next generation photovoltaics. This paper presents two kinds of polymer/polymer blend solar cells to exemplify the potential advantages compared with conventional organic solar cells. The large difference in the HOMO/LUMO levels of donor/acceptor polymers results in a high voltage, and the large absorptivity up to near-infrared wavelengths allows to increase the photocurrent density. These characteristics are brought by development of a variety of low bandgap polymers. For the further improvement of conversion efficiency, it is a crucial issue to control the phase-separation structure on a nanometer scale.

Morphology‐Limited Free Carrier Generation in Donor/Acceptor Polymer Blend Solar Cells Composed of Poly(3‐hexylthiophene) and Fluorene‐Based Copolymer

“…As expected, much higher V OC of 1.26 V was yielded when compared to P3HT/PCBM devices, which typically yield values of only about 0.6 V. [9][10][11] In addition, thermal annealing improved both the J SC and the FF, resulting in a PCE of 2.7%. [ 10,11 ] However, the maximum external quantum effi ciency (EQE) of the P3HT/PF12TBT BHJ solar cells was just 30%, far below the 70-80% values reported for P3HT/PCBM devices. [ 2 ] This means that the high V OC of this The charge generation and recombination dynamics in polymer/polymer blend solar cells composed of poly(3-hexylthiophene) (P3HT, electron donor) and poly[2,7-(9,9-didodecylfl uorene)-alt -5,5-(4′,7′-bis(2-thienyl)-2′,1′,3′-benzothiadiazole)] (PF12TBT, electron acceptor) are studied by transient absorption measurements.…”

“…Recently, we reported a polymer/ polymer BHJ solar cell containing poly(3-hexylthiophene) (P3HT) as the donor and poly[2,7-(9,9-didodecylfl uorene)-alt -5,5-(4′,7′-bis(2-thienyl)-2′,1′,3′-benzothiadiazole)] (PF12TBT) as the acceptor ( Figure 1 a). [9][10][11] This system gave an energy difference of more than 1 eV between the highest occupied molecular orbital (HOMO) of the donor and the LUMO of the acceptor, retaining the 0.8 eV offset in the HOMO-HOMO and the LUMO-LUMO levels needed for effi cient charge transfer ( Figure 1 ). As expected, much higher V OC of 1.26 V was yielded when compared to P3HT/PCBM devices, which typically yield values of only about 0.6 V. [9][10][11] In addition, thermal annealing improved both the J SC and the FF, resulting in a PCE of 2.7%.…”

“…[9][10][11] This system gave an energy difference of more than 1 eV between the highest occupied molecular orbital (HOMO) of the donor and the LUMO of the acceptor, retaining the 0.8 eV offset in the HOMO-HOMO and the LUMO-LUMO levels needed for effi cient charge transfer ( Figure 1 ). As expected, much higher V OC of 1.26 V was yielded when compared to P3HT/PCBM devices, which typically yield values of only about 0.6 V. [9][10][11] In addition, thermal annealing improved both the J SC and the FF, resulting in a PCE of 2.7%. [ 10,11 ] However, the maximum external quantum effi ciency (EQE) of the P3HT/PF12TBT BHJ solar cells was just 30%, far below the 70-80% values reported for P3HT/PCBM devices.…”

“…[ 4,5 ] Owing to considerable efforts in synthesizing polymer acceptors and optimizing the blend morphology, the PCEs of polymer/polymer BHJ solar cells have been improved up to more than 5% in the last few years. [ 7 ] Fluorene and benzothiadiazole-based copolymers are among the most promising of these acceptor alternatives [8][9][10][11] because of their large absorption coeffi cients in the visible region and higher energy levels for the lowest unoccupied molecular orbital (LUMO); these features in turn increase light absorption and V OC , respectively. Recently, we reported a polymer/ polymer BHJ solar cell containing poly(3-hexylthiophene) (P3HT) as the donor and poly[2,7-(9,9-didodecylfl uorene)-alt -5,5-(4′,7′-bis(2-thienyl)-2′,1′,3′-benzothiadiazole)] (PF12TBT) as the acceptor ( Figure 1 a).…”

Advances in Non‐Fullerene Acceptor Based Ternary Organic Solar Cells

“…Near‐IR dye molecules have also been used as the third components in non‐fullerene OSCs for further improvement of PCE. Lee et al introduced a silicon naphthalocyanine (SiNc) derivative as a NIR sensitizer into P3HT/N2200 all‐polymer blends to improve light absorptivity. For the P3HT/SiNc/N2200 ternary cells, the J sc was improved significantly in comparison to that of the original binary cells.…”