Dramatically Boosted Efficiency of Small Molecule Solar Cells by Synergistically Optimizing Molecular Aggregation and Crystallinity

For the given organic donor and acceptor materials, optimizing molecular aggregation and crystallinity for appropriate phase separation plays a crucial role in achieving high performance solar cells. In this study, the power conversion efficiency (PCE) of DR3TSBDT:PC₇₁BM based small molecule solar cells (SMSCs) was markedly raised from 7.25% to 9.48% for active layers processed with 0.2 vol % 1,8-diiodooctane (DIO), resulting from the improved fill factor (FF) and short circuit current density (<i>J</i>_SC). The performance improvement may be attributed to an appropriate DR3TSBDT molecular aggregation and crystallinity, as well as the optimized phase separation. The influence of DIO concentrations on DR3TSBDT molecular aggregation can be confirmed from the red-shifted absorption and photoluminescence peaks of films along with increase of DIO concentrations. Meanwhile, the ratio of hole/electron mobility approached 1.06 in the optimized SMSCs well according with the highest FF of the corresponding SMSCs. The morphology characterizations indicate that DR3TSBDT molecular aggregation and crystallinity could be finely adjusted by doping appropriate DIO additive

Improved Performance of Photomultiplication Polymer Photodetectors by Adjustment of P3HT Molecular Arrangement

A series of photomultiplication (PM)-type polymer photodetectors (PPDs) were fabricated with polymer poly­(3-hexylthiophene)–[6,6]-phenyl-C₇₁-butyric acid methyl ester (P3HT–PC₇₁BM) (100:1, w/w) as the active layers, the only difference being the self-assembly time of the active layers for adjusting the P3HT molecular arrangement. The grazing incidence X-ray diffraction (GIXRD) results exhibit that P3HT molecular arrangement can be adjusted between face-on and edge-on structures by controlling the self-assembly time. The champion EQE value of PPDs, based on the active layers without the self-assembly process, arrives at 6380% under 610 nm light illumination at −10 V bias, corresponding to the face-on molecular arrangement of P3HT in the active layers. The EQE values of PPDs were markedly decreased to 1600%, along with the self-assembly time up to 12 min, which should be attributed to the variation of absorption and hole transport ability of the active layers induced by the change of P3HT molecular arrangement. This finding provides an effective strategy for improving the performance of PM-type PPDs by adjusting the molecular arrangement, in addition to the enhanced trap-assisted charge-carrier tunneling injection

Simultaneously Enhanced Efficiency and Stability of Polymer Solar Cells by Employing Solvent Additive and Upside-down Drying Method

The morphology of active layer plays an important role in determining the power conversion efficiency (PCE) and stability of polymer solar cells (PSCs), which strongly depend on the dynamic drying process of active layer. In this work, an efficient and universal method was developed to let active layer undergo upside-down drying process in a covered glass Petri dish. For the PSCs based on PTB7-Th:PC₇₁BM, the champion PCEs were improved from 8.58% to 9.64% by mixing 3 vol % 1,8-di-iodooctane and further to 10.30% by employing upside-down drying method. The enhanced PCEs of PSCs with active layers undergoing upside-down drying process are mainly attributed to the optimized vertical phase separation, the more ordered and tightly packed π–π stacking of polymer molecules. Meanwhile, PC₇₁BM molecules can be frozen in more ordered and tightly packed π–π stacking polymer network, which lead to the enhanced stability of PSCs. The universality of upside-down drying method can be solidly confirmed from PSCs with PTB7:PC₇₁BM, PffBT4T-2OD:PC₇₁BM, or PBDT-TS1:PC₇₁BM as active layers, respectively. The molecular packing and phase separation of blend films with different solvent additives and drying methods were investigated by grazing incidence X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy

Improved Efficiency of Bulk Heterojunction Polymer Solar Cells by Doping Low-Bandgap Small Molecules

We present performance improved ternary bulk heterojunction polymer solar cells by doping a small molecule, 2,4-bis­[4-(<i>N,N</i>-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIB-SQ), into the common binary blend of poly­(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). The optimized power conversion efficiency (PCE) of P3HT:PC₇₁BM-based cells was improved from 3.05% to 3.72% by doping 1.2 wt % DIB-SQ as the second electron donor, which corresponds to ∼22% PCE enhancement. The main contributions of doping DIB-SQ material on the improved performance of PSCs can be summarized as (i) harvesting more photons in the low-energy range, (ii) increased exciton dissociation, energy transfer, and charge carrier transport in the ternary blend films. The energy transfer process from P3HT to DIB-SQ is demonstrated by time-resolved transient photoluminescence spectra through monitoring the lifetime of 700 nm emission from neat P3HT, DIB-SQ and blended P3HT:DIB-SQ solutions. The lifetime of 700 nm emission is increased from 0.9 ns for neat P3HT solution, to 4.9 ns for neat DIB-SQ solution, to 6.2 ns for P3HT:DIB-SQ blend solution

Ternary Nonfullerene Polymer Solar Cells with a Power Conversion Efficiency of 11.6% by Inheriting the Advantages of Binary Cells

Ternary polymer solar cells (PSCs) were commonly fabricated with two donors or two acceptors; the third component has complementary absorption spectra with a host system to improve photon harvesting. In this work, a series of nonfullerene PSCs were fabricated with J71 as the donor and IT-M and/or ITIC with an almost identical band gap as acceptors. Although IT-M and ITIC have almost identical band gaps, the two optimized binary PSCs exhibit different photovoltaic parameters. The short current density (<i>J</i>_sc) and open-circuit voltage (<i>V</i>_oc) of J71:IT-M based PSCs are larger than those of J71:ITIC based PSCs; the other key parameter, the fill factor (FF), is just the opposite. The power conversion efficiency (PCE) of optimized ternary PSCs arrives at 11.60% by inheriting the advantages of binary PSCs. This work may provide a new strategy for preparing efficient nonfullerene ternary PSCs by selecting binary PSCs with complementary photovoltaic parameters

Simultaneous Improvement in Short Circuit Current, Open Circuit Voltage, and Fill Factor of Polymer Solar Cells through Ternary Strategy

We present a smart strategy to simultaneously increase the short circuit current (<i>J</i>_sc), the open circuit voltage (<i>V</i>_oc), and the fill factor (FF) of polymer solar cells (PSCs). A two-dimensional conjugated small molecule photovoltaic material (SMPV1), as the second electron donor, was doped into the blend system of poly­(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C71-butyric acid methyl (PC₇₁BM) to form ternary PSCs. The ternary PSCs with 5 wt % SMPV1 doping ratio in donors achieve 4.06% champion power conversion efficiency (PCE), corresponding to about 21.2% enhancement compared with the 3.35% PCE of P3HT:PC₇₁BM-based PSCs. The underlying mechanism on performance improvement of ternary PSCs can be summarized as (i) harvesting more photons in the longer wavelength region to increase <i>J</i>_sc; (ii) obtaining the lower mixed highest occupied molecular orbital (HOMO) energy level by incorporating SMPV1 to increase <i>V</i>_oc; (iii) forming the better charge carrier transport channels through the cascade energy level structure and optimizing phase separation of donor/acceptor materials to increase <i>J</i>_sc and FF

CCI surgery decreases NAD and increases NAM in the spinal cord.

<p>CCI surgery decreases (A) NAD and increases (B) NAM as compared with sham surgery. (C) The ratio of NAD/NAM is decreased in CCI mice as compared with that in sham group. (D) NAM and NAD fractions are collected according to HPLC method. The arrows show the retention time of NAM and NAD, which is at around 21 min and 48 min, respectively. The NAM peaks are mixed with those of other impurities. (E) Spectrograms of NAD with MALDI-MS are representative results from a sham-treated (left) and a CCI-treated (right) mouse. The position of NAD and ¹⁸O NAD are indicated. (F) Spectrograms of NAM with ESI-MS are representative results from a sham-treated (left) and a CCI-treated (right) mouse. The position of NAM is indicated. <i>n</i> = 6 at each time point in each group; ^*<i>P</i><0.05, ^**<i>P</i><0.01 <i>vs.</i> sham group at each time point. NAM, nicotinamide; NAD, nicotinamide adenine dinucleotide; CCI, chronic constriction injury; MALDI-MS, matrix-assisted laser desorption ionization-mass spectroscopy; ESI-MS, electrospray ionization-mass spectrometry.</p

EX-527 inhibits the anti-nociceptive effect of resveratrol.

<p>Intrathecal injection of 5 µl EX-527 (1.2 mM) 1 h before resveratrol administration effectively reverses the effect of resveratrol (45 mM) delaying the onset of (A) thermal hyperalgesia and (B) mechanical allodynia produced by CCI surgery. (C) EX-527 inhibits the effect of resveratrol attenuating CCI-induced elevation of H4-K16Ac 1 day after CCI surgery. (D) Quantification of the immunoblots shows that EX-527 inhibits the effects of resveratrol on H4-K16Ac. An arrow indicates a resveratrol injection and a dotted arrow indicates an EX-527 injection. <i>n</i> = 10 in each group for behavior test and <i>n</i> = 6 in each group for H4-K16Ac analysis; ^*<i>P</i><0.05, ^**<i>P</i><0.01 <i>vs.</i> DMSO-DMSO-treated CCI group; ^#<i>P</i><0.05, ^##<i>P</i><0.01 <i>vs.</i> resveratrol-DMSO-treated CCI group. CCI, chronic constriction injury; H4-k16Ac, H4-k16 acetylation; DMSO, dimethyl sulfoxide.</p

CCI surgery decreases spinal SIRT1 content and this is associated with an increase in pain-related behaviors.

<p>(A) Spinal SIRT1 content is decreased 1, 3, 7, 14 and 21 days after CCI surgery as compared with that after sham surgery. (B) Quantification of the immunoblots shows that SIRT1 levels are decreased after CCI surgery. CCI surgery induces (C) thermal hyperalgesia and (D) mechanical allodynia in ipsolateral hind paw. <i>n</i> = 12 in each group for behavioral test and <i>n</i> = 6 at each time point in each group for SIRT1 analysis; ^*<i>P</i><0.05, ^**<i>P</i><0.01 <i>vs.</i> sham group at each time point. CCI, chronic constriction injury; SIRT1, silent information regulator 1.</p

CCI surgery increases acetylation of H4-k16.

<p>(A) The levels of H4-k16Ac, but not total H4, are increased 1, 3, 7, 14 and 21 days after CCI surgery as compared with those after sham surgery. (B) Quantification of the immunoblots shows that H4-k16Ac is increased after CCI surgery. <i>n</i> = 6 at each time point in each group; ^*<i>P</i><0.05, ^**<i>P</i><0.01 <i>vs.</i> sham group at each time point. CCI, chronic constriction injury; SIRT1, silent information regulator 1; H4-k16Ac, H4-k16 acetylation.</p