Search

None-fullerene solar cells with ternary architecture have attracted much attention because it is an effective approach for boosting the device power conversion efficiency. Here, the crystalline polymer N2200 as the third component is integrated into J71: ITIC bulk heterojunction. A series of characterizations indicate that N2200 could increase photo-harvesting, balanced hole and electron mobilities, enhanced exciton dissociation, and suppressed charge recombination, which result in the comprehensive improvement of open circuit voltage, short circuit current and fill factor in the device. Moreover, after introduction of N2200, the morphology of the ternary active layer is optimized, and the film crystallinity is improved. This work demonstrates that adding a small quantity of high crystallization acceptor into non-fullerene donor: acceptor mixture is a promising strategy toward developing high-performance organic solar cells. Funding Agencies|National Science Foundation of China [11604099, 21875067, 51873138, 51811530011]; Shanghai Rising -Star [19QA1403100]; Shanghai Science and Technology Innovation Action Plan [17JC1402500]; National Key Project for Basic Research of China [2017YFA0303403]; Swedish Research Council [2016-05498]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; STINT grant [CH2017-7163]

Interfacial compatibility between the electrode and organic semiconductor plays a critical role in controlling the charge transport and hence efficiency of organic solar cell. Here, we introduce a novel small-molecule zwitterionic electrolyte (S1) combined with ZnO as electron transporting interlayer employed for the inverted PTB7:PC71BM bulk heterojunction solar cell. The resulting device with the S1/ZnO stacked interlayer achieves a high PCE of 8.59%, obtaining a 16.2% improvement over the control device performance of 7.4% without the S1 attributed to the significant increased short-circuit current density and fill factor. The interfacial properties are investigated. It is found that the S1/ZnO interlayer possess an ultralow work function of 3.6 eV, which originates from the interfacial double dipole step induced by the zwitterionic side chain electrostatic realignment at interface. The S1/ZnO interlayer exhibits the excellent charge extraction ability, suppresses the charge recombination loss and decreases the series resistance at the active layer/electrode contact.

Morphology optimization of donor–acceptor bulk heterojunctions at microscopic scale is critical for improving performance of organic photovoltaic devices. Here, effects of thermal annealing on phase separation processes in small-molecular bulk heterojunctions with different geometrical structures (i.e., PTCDA, TiOPc, CuPc and C60) are investigated with ultraviolet and X-ray photoemission spectroscopies. It was identified that post-annealing treatment caused the different degrees of vertical diffusions at the bulk heterojunctions, leading to non-uniform composition distributions. Variations in phase separations are mainly due to the differences in surface energy of the involved materials, which play a crucial role in the intermolecular interactions and the molecular diffusion. Low-surface-energy materials were found to segregate preferentially on the surface for minimizing total energy of the systems.

High performance inverted polymer solar cell is demonstrated by introducing a nanostructured backscattering rear electrode, which is fabricated by embedding silver nanoparticle (NP) arrays into the MoO3 hole extraction layer. As verified by characterizing and simulating the electrical and optical properties, such a nanostructured rear electrode can achieve an improved cell performance by maintaining simultaneously high open-circuit voltage and fill factor values, while providing excellent short-circuit current enhancement through efficient backscattering-induced light trapping. A careful optimization of the nanostructured rear electrode can result in polymer solar cells with an enhanced power conversion efficiency of 7.21%, as compared to 6.26% of the reference cell with a flat electrode. It is noteworthy that the method described here offers a convenient and scalable way for inexpensive and high-performance polymer solar cell designs.

An efficient inverted polymer solar cell (PSC) is reported by integrating a small molecular electron collection layer (ECL) between indium tin oxide (ITO) cathode and the photoactive layer of blended poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM). The ECL is composed of a cesium carbonate-doped tris(8-hydroxyquinolinato) aluminum (Cs2CO3:Alq3) layer. As determined by photoelectron spectroscopy and electrical measurements, the Cs2CO3 doping induces suitable energy level alignment at the ITO/Cs2CO3:Alq3/PCBM interface and the increase in bulk conductivity of organic ECL, which are favorable to electron extraction through Cs2CO3:Alq3 to ITO cathode. In addition, optical simulation indicates that the Cs2CO3:Alq3 layer can act as an optical spacer to modulate the region of highest incident light intensity within the photoactive layer, where absorption and charge dissociation are efficient. The inverted PSC with an optimized Cs2CO3:Alq3 ECL exhibits a power conversion efficiency of 4.83%. The method reported here provides a facile approach to achieve high-performance inverted PSCs at low processing temperature.

An efficient inverted polymer solar cell is enabled by incorporating an n-type doped wide-gap organic electron transporting layer (ETL) between the indium tin oxide cathode and the photoactive layer for electron extraction. The ETL is formed by a thermal-deposited cesium carbonate-doped 4,7-diphenyl-1,10-phenanthroline (Cs 2 CO 3 :BPhen) layer. The cell response parameters critically depended on the doping concentration and film thickness of the Cs 2 CO 3 :BPhen ETL. Inverted polymer solar cell with an optimized Cs 2 CO 3 :BPhen ETL exhibits a power conversion efficiency of 4.12% as compared to 1.34% for the device with a pristine BPhen ETL. The enhanced performance in the inverted device is associated with the favorable energy level alignment between Cs 2 CO 3 :BPhen and the electron-acceptor material, as well as increased conductivity in the doped organic ETL for electron extraction. The method reported here provides a facile approach to optimize the performance of inverted polymer solar cells in terms of easy control of film morphology, chemical composition, conductivity at low processing temperature, as well as compatibility with fabrication on flexible substrates.

An efficient inverted polymer solar cell (PSC) is reported by employing an atomic layer deposited (ALD) cadmium sulfide (CdS) film between the indium tin oxide (ITO) cathode and the photoactive layer as the electron collection layer (ECL), on which a active layer is composed of a blended poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) bulk heterojunction. As determined by photoelectron spectroscopy, the sulfur vacancy induces an n-type semiconducting property in the ALD-grown CdS films, and suitable energy level alignment at the ITO/CdS/PCBM interface is favorable to electron extraction through CdS to the ITO electrode. With the optimized CdS film thickness, the power conversion efficiency increases to 3.33%, with short-circuit current of 8.94 mA/cm2, open-circuit voltage of 0.61 V, and fill factor of 61.1% under AM1.5G 100 mW/cm2 irradiation.