Jiao Zhao

The Effects of Improved Photoelectric Properties of PEDOT:PSS by Two-Step Treatments on the Performance of Polymer Solar Cells Based on PTB7-Th:PC71BM

UNLABELLED In this paper, we present a smart two-step treated method to simultaneously improve the work function, conductivity, and transmittance of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PEDOT PSS). With the two-step treated PEDOT PSS, the short-circuit current density of polymer solar cells (PSCs) based on PTB7-Th:PC71BM increases from 13.41 to 22.10 mA/cm(2), and the power conversion efficiency increases from 7.35% to 9.82% with 33% improvement. The underlying mechanisms on performance improvement of PSCs can be summarized as follows: (1) two-step treated PEDOT PSS with the improved work function and the conductivity, which contributes significantly to the charge collection of PSCs; and (2) two-step treated PEDOT PSS with higher transmittance, which is of benefit to the light absorption of the active layer in PSCs.

Improving charge transport by the ultrathin QDs interlayer in polymer solar cells

Lead sulfide (PbS) quantum dots (QDs) have been incorporated into PTB7:PC71BM BHJ active layers to fabricate polymer solar cells (PSCs) and gather on the top surface of active layers to form an ultrathin interlayer. The PbS QDs ultrathin interlayer with an appropriate thickness increases the carrier transport capacity, exciton dissociation and reduces the carrier recombination, which leads to a higher short circuit current (Jsc) and fill factor (FF). Finally, the power conversion efficiency (PCE) improves from 7.03% (control devices) to 7.87% with an ultrathin interlayer by doping 5% PbS QDs, while the current density (Jsc) and fill factor (FF) enhances from 13.83 mA cm−2 to 14.81 mA cm−2 and from 68.70% to 70.85%, respectively.

An additive dripping technique using diphenyl ether for tuning perovskite crystallization for high-efficiency solar cells

Controlling the morphology of the MAPbI3−xClx active layer has remained a challenge towards advancing perovskite solar cells (PvSCs). Here, we demonstrate that a low temperature additive dripping (AD) treatment step, using diphenyl ether (DPE), can significantly improve the power conversion efficiency (PCE), compared to the control device using chlorobenzene (CB), by 15% up to 16.64%, with a high current density (JSC) of 22.67 mA/cm2. We chose DPE for its small and appropriate dipole moment to adjust the solubility of the MAPbI3−xClx precursor during the formation of the intermediate phase and the MAPbI3−xClx phase. The low DPE vapor pressure provides a longer processing window for the removal of residual dimethylformamide (DMF), during the annealing process, for improved perovskite formation. Imaging and X-ray analysis both reveal that the MAPbI3−xClx film exhibits enlarged grains with increased crystallinity. Together, these improvements result in reduced carrier recombination and hole trap-state density in the MAPbI3−xClx film, while minimizing the hysteresis problem typical of PvSCs. These results show thatthe AD approach is a promising technique for improving PvSCs.

Improving the Charge Carrier Transport and Suppressing Recombination of Soluble Squaraine-Based Solar Cells via Parallel-Like Structure

Small molecule organic solar cells (SMOSCs) have attracted extensive attention in recent years. Squaraine (SQ) is a kind of small molecule material for potential use in high-efficiency devices, because of its high extinction coefficient and low-cost synthesis. However, the charge carrier mobility of SQ-based film is much lower than other effective materials, which leads to the pretty low fill factor (FF). In this study, we improve the performance of SQ derivative-based solar cells by incorporating PCDTBT into LQ-51/PC71BM host binary blend film. The incorporation of PCDTBT can not only increase the photon harvesting, but also provide an additional hole transport pathway. Through the charge carrier mobility and transient photovoltage measurement, we find that the hole mobility and charge carrier lifetime increase in the ternary system. Also, we carefully demonstrate that the charge carrier transport follows a parallel-like behavior.

PEOz-PEDOT:PSS Composite Layer: A Route to Suppressed Hysteresis and Enhanced Open-Circuit Voltage in a Planar Perovskite Solar Cell

The successful commercialization of perovskite solar cells (Pvs-SCs) calls for the need to find low-temperature processable interlayers with outstanding charge-transport features. In this work, we strategically blend poly(2-ethyl-2-oxazoline) (PEOz) with PEDOT:PSS as the modified hole transport layer (HTL) to achieve high-efficiency P-I-N CH3NH3PbI3 Pvs-SCs. The PEOz-PEDOT:PSS HTL exhibits enhanced features over the conventional layer including the following: (1) promoting perovskite with enlarged grain sizes to decrease the perovskite layers recombination, (2) increasing the work function of the HTL, and (3) decreasing the noncapacitive current in Pvs-SCs. Remarkably, we demonstrate a 17.39% power conversion efficiency with very low hysteresis and high Voc values of 1.075 V for Pvs-SCs with PEOz-PEDOT:PSS.

Highly Efficient and Operational Stability Polymer Solar Cells Employing Nonhalogenated Solvents and Additives

The power conversion efficiencies (PCEs) of potential polymer solar cells have been shown to rapidly exceed 15%. However, these high-performance devices are based on halogenated solvents that pose a significant hazard to the atmospheric environment and human beings. The use of nonhalogenated solvents makes the device less efficient because of its solubility issues. In this work, we report high-efficiency devices utilizing PffBT4T-2OD and [6,6]-phenyl C71 butyric acid methyl ester system from nonhalogenated solvents such as o-xylene ( o-XY) and 1-methylnaphthalene (Me) hydrocarbon solvent. When Me was used as the additive, the PCE of prepared devices improved from 1.83 to 10.13%, which is rather higher than that of the devices processed with traditional solvents combined with chlorobenzene and 1,8-diiodooctane (8.18%). Both atomic force microscopy and transmission electron microscopy confirmed that after nonhalogen solvents are treated, a more finely phase-separated dense morphology of active layers than after halogen solvents. At the same time, grazing incident wide-angle X-ray scattering patterns show that the combination of nonhalogenated solvents o-XY and Me ingeniously formed an ordered crystal and π-π stacking. Also, the stability of devices prepared from nonhalogenated solvents was significantly better than that of halogenated solvents under continuous illumination in the air without encapsulation.