TY  - JOUR
A1  - Jiang, Wei
A1  - Tao, Chen
A1  - Stolterfoht, Martin
A1  - Jin, Hui
A1  - Stephen, Meera
A1  - Lin, Qianqian
A1  - Nagiri, Ravi C. R.
A1  - Burn, Paul L.
A1  - Gentle, Ian R.
T1  - Hole-transporting materials for low donor content organic solar cells
BT  - charge transport and device performance
JF  - Organic electronics : physics, materials and applications
N2  - Low donor content solar cells are an intriguing class of photovoltaic device about which there is still considerable discussion with respect to their mode of operation. We have synthesized a series of triphenylamine-based materials for use in low donor content devices with the electron accepting [6,6]-phenyl-C71-butyric acid methyl ester (PC(7)0BM). The triphenylamine-based materials absorb light in the near UV enabling the PC(7)0BM to be be the main light absorbing organic semiconducting material in the solar cell. It was found that the devices did not operate as classical Schottky junctions but rather photocurrent was generated by hole transfer from the photo-excited PC(7)0BM to the triphenylamine-based donors. We found that replacing the methoxy surface groups with methyl groups on the donor material led to a decrease in hole mobility for the neat films, which was due to the methyl substituted materials having the propensity to aggregate. The thermodynamic drive to aggregate was advantageous for the performance of the low donor content (6 wt%) films. It was found that the 6 wt% donor devices generally gave higher performance than devices containing 50 wt% of the donor.
KW  - photoexcited hole transfer
KW  - photocurrent generation
KW  - synthesis
KW  - hole
KW  - mobility
KW  - low donor content
KW  - Schottky junction
Y1  - 2020
U6  - https://doi.org/10.1016/j.orgel.2019.105480
SN  - 1566-1199
SN  - 1878-5530
VL  - 76
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Alqahtani, Obaid
A1  - Babics, Maxime
A1  - Gorenflot, Julien
A1  - Savikhin, Victoria
A1  - Ferron, Thomas
A1  - Balawi, Ahmed H.
A1  - Paulke, Andreas
A1  - Kan, Zhipeng
A1  - Pope, Michael
A1  - Clulow, Andrew J.
A1  - Wolf, Jannic
A1  - Burn, Paul L.
A1  - Gentle, Ian R.
A1  - Neher, Dieter
A1  - Toney, Michael F.
A1  - Laquai, Frederic
A1  - Beaujuge, Pierre M.
A1  - Collins, Brian A.
T1  - Mixed Domains Enhance Charge Generation and Extraction in Bulk-Heterojunction Solar Cells with Small-Molecule Donors
JF  - Advanced energy materials
N2  - The interplay between nanomorphology and efficiency of polymer-fullerene bulk-heterojunction (BHJ) solar cells has been the subject of intense research, but the generality of these concepts for small-molecule (SM) BHJs remains unclear. Here, the relation between performance; charge generation, recombination, and extraction dynamics; and nanomorphology achievable with two SM donors benzo[1,2-b:4,5-b]dithiophene-pyrido[3,4-b]-pyrazine BDT(PPTh2)(2), namely SM1 and SM2, differing by their side-chains, are examined as a function of solution additive composition. The results show that the additive 1,8-diiodooctane acts as a plasticizer in the blends, increases domain size, and promotes ordering/crystallinity. Surprisingly, the system with high domain purity (SM1) exhibits both poor exciton harvesting and severe charge trapping, alleviated only slightly with increased crystallinity. In contrast, the system consisting of mixed domains and lower crystallinity (SM2) shows both excellent exciton harvesting and low charge recombination losses. Importantly, the onset of large, pure crystallites in the latter (SM2) system reduces efficiency, pointing to possible differences in the ideal morphologies for SM-based BHJ solar cells compared with polymer-fullerene devices. In polymer-based systems, tie chains between pure polymer crystals establish a continuous charge transport network, whereas SM-based active layers may in some cases require mixed domains that enable both aggregation and charge percolation to the electrodes.
KW  - charge transport
KW  - domain purity
KW  - microscopy
KW  - mixed domains
KW  - organic solar cells
KW  - photovoltaic devices
KW  - resonant X-ray scattering
KW  - small molecules
KW  - transient spectroscopy
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201702941
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 19
PB  - Wiley-VCH
CY  - Weinheim
ER  -