Corrigendum: Impact of Polymer Backbone Fluorination on the Charge Generation/Recombination Patterns and Vertical Phase Segregation in Bulk Heterojunction Organic Solar Cells

Highly Efficient Large Area Organic Photovoltaic Module with 350 nm Thick Active Layer using Random Terpolymer Donor

摘要： Random terpolymers are developed by incorporating small portions of benzodithiophene into a highly crystalline copolymer of terthiophene and difluorobenzothiadiazole, BDT-Th0. The bulk-heterojunction (BHJ) of the copolymer BDT-Th0 is formed by process of rapid solid-liquid phase demixing of polymer crystallites, which results in irregular and unclear phase separation with large polymer aggregation. By contrast, the random terpolymer BDT-Th10 which was prepared using 10% feed molar ratio of a benzodithiophene moiety shows slower and gradual formation of the polymer packing structures without substantial agglomeration from loosely packed pseudo-crystallites in precursor solution. This results in optimal BHJ morphology with appropriate phase separation and improved domain purity. BDT-Th10 achieves high solar cell efficiency of 7.74% by successfully reproducing the optimized BHJ morphology of small cells into 58.5 cm2 sized modules with 350 nm film thickness, whereas the copolymer shows irreproducible property with much decreased efficiency of 4.37%. This result is among the highest efficiency of high-performance large area PSC modules with such a thick active film.

Photovoltaic Properties of a Conjugated Copolymer Blending with Flame-Made ZnO Nanoparticles

摘要： The synthesis, characterizations, and photovoltaic studies of copolymer based on 4,4-dodecylpentaleno[1,2-b]dithiophene (PC12PDT) and 5-octyl-5H-thieno[3,4-c]pyrrole-4,6-dione (TPD) were described. The PC12PDTTPD copolymer achieved a high open circuit voltage (Voc) of ~ 0.8?0.9 V. Bulk-heterojunction (BHJ) solar cells were fabricated by using chlorobenzene with 1% chloronapthalene as the solvent additive. The ZnO nanoparticles, produced by flame spray pyrolysis (FSP), were dispersed in 1-butanol. After that, it was loaded into the devices along with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) used as the electron acceptor. From the results, it was found that the ZnO nanoparticles with different amount had the effect on the power conversion efficiency (PCE) of the solar cells. The PCE obtained in this study (3.33%) was found in the 5.45 wt% ZnO loaded device. This was an improvement as compared to that of the standard device (2.45%).

Interfacial and Bulk Nanostructures Control Loss of Charges in Organic Solar Cells

摘要： Organic solar cells (OSCs) have emerged as one promising sustainable energy resource since the introduction of state-of-the-art bulk heterojunction (BHJ) device structure in early 1990s. Impressively developed molecular design methodologies in the past decade have led researchers toward utilizing more suitable pairs of low (p-type) and high (n-type) electron affinity organic semiconducting materials. Among other attributes, versatile absorption capabilities of these versatile organic materials may lead to explicit interfaces, phase distributions, and crystalline nanostructures. Structural characterization techniques involving soft and hard X-rays have enabled us to measure these morphology parameters quantitatively including their strong correlation with photovoltaic (PV) parameters. Favorable processing techniques have been adopted to realize auspicious interfacial areas and charge percolations in bulk toward efficient short circuit current (JSC) and fill factor (FF) values. Collaborative efforts in the fields of chemical structure design of materials, device characterization, and engineering have pushed the power conversion efficiencies (PCEs) of OSCs to 16%. However, the single layer BHJ structure still requires further optimizations for the extension of their PCEs toward the theoretical limit.

Performance enhancement of bulk heterojunction organic solar cells using photon upconverter

摘要： In this article, we show that significant performance enhancement can be obtained by incorporating a photo upconverter layer in bulk heterojunction organic solar cells (BHJ OSCs). We systematically optimize the photon upconversion process for P3HT:PCBM, PSBTBT:PCBM, PBDTTT-C:PCBM and PTB7-Th:PCBM based BHJ OSCs using a simple numerical model followed by optoelectronic simulations. After verifying the integrated model of upconversion with experimental reports, we analyze each type of BHJ OSC incorporating photon upconversion layer having optimized spectral characteristics and estimate efficiency enhancement of ~30.8% (4.55% → 5.95%), ~24.3% (5.02% → 6.24%), ~28.9% (6.35% → 8.19%) and ~16.9% (10.55% → 12.34%) for P3HT:PCBM, PSBTBT:PCBM, PBDTTT-C:PCBM and PTB7-Th:PCBM based OSCs, respectively. We then show that effect of photon upconversion and localized surface plasmon resonance on the best performing OSC material considered in this work i.e. PTB7-Th:PCBM, is non-linear and predict a performance boost of mere ~2.3% (12.32% → 12.62%) from additional effort (due to plasmon resonance). Finally, we discuss possibility of extending the efficiency of PTB7-Th:PCBM based BHJ OSC beyond 16% using concentrated sunlight and a practically realizable upconverter layer.

A symmetric benzoselenadiazole based D–A–D small molecule for solution processed bulk-heterojunction organic solar cells

摘要： Benzoselenadiazole as the central acceptor unit with terminal donor unit of n-hexylbithiophene was chosen to design the symmetric donor-acceptor-donor (D–A–D) configuration based small organic chromophore, 4,7-bis(50-hexyl-[2,20-bithiophen]-5-yl)benzo[c][1,2,5]selenadiazole, RTh-BSe-ThR, for the fabrication of solution-processed bulk-heterojunction organic solar cells (BHJ-OSCs). RTh-BSe-ThR chromophore showed assuring solubility in common organic solvents and exhibited wider absorption in the visible region with an optical band gap (Eg opt) of ~1.87 eV. Benzoselenadiazole unit with two n-hexylbithiophene units exhibited an excellent electrochemical behavior with the highest occupied molecular orbital (HOMO) of ~5.38 eV and the lowest unoccupied molecular orbital (LUMO) of ~3.51 eV. The fabricated BHJ-OSCs with RTh-BSe-ThR:PC61BM (1:3, w/w) blend thin film displayed a power conversion efficiency (PCE) of ~3.46% and a high value of short circuit current density (JSC) of ~11.20 mA/cm2. The enhancement in the photovoltaic parameters might be attributed to the significant improvements in the interfacial area of bulk heterojunction which might enhance the light harvesting property and the shunt resistance of the blend thin films.

Graphene oxide-doped PEDOT:PSS as hole transport layer in inverted bulk heterojunction solar cell

摘要： Transparent poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) is widely used hole conducting material in optoelectronic devices. Secondary doping of PEDOT:PSS enables the tunability of its electronic properties. In this work, graphene oxide (GO) was used as a secondary dopant for PEDOT:PSS and the doped materials (composites) were tested for their efficiency as hole transport material in inverted bulk heterojunction (BHJ) solar cell. The composites were studied to unveil the effects of Coulombic interaction between GO and PEDOT:PSS where we note some segregation of PEDOT phase. We found that the GO majorly interacts with PSS through oxygeneous functional groups which promote the detachment of PEDOT from PSS and segregation of PEDOT. Electrochemical properties with and without illumination revealed some photo-induced changes to surface of the samples. Device performances showed about 2.2% efficiency enhancement when GO doping level was 0.25 (v:v) when compared to that of pristine PEDOT:PSS.

Influence of active layer thickness on photovoltaic performance of PTB7:PC70BM bulk heterojunction solar cell

摘要： In this paper, we studied the effect of active layer thickness on the photovoltaic performance of inverted bulk heterojunction (BHJ) organic solar cell (OSC). The capacitance-voltage (C–V), dark current-voltage (I–V) and impedance spectroscopy (IS) analysis were carried out to explain the active layer thickness dependence on the photovoltaic performance. The OSC with an active layer thickness of 150 nm achieved the best power conversion efficiency (PCE) of 5.87%, while the OSC of 200 nm active layer thickness yielded the worst PCE. Reduction in the fill factor (FF) was the main reason for the reduction in the PCE at large active layer thickness. The dark I–V analysis revealed large defect density for the OSC with active layer thickness of 200 nm, which raised the charge recombination and leakage current and consequently reduced the FF. IS analysis predicted that the charge transport became the serious limitations for the OSC with 200 nm thick active layer, which can be attributed to the weakening of electric field as well as creation of field-free regions. It mainly caused a drastic drop in the fill factor by reducing the charge collection efficiency, consequently deteriorated the photovoltaic performance.

5H-Fluoreno [3,2- b:6,7- b’] Dithiophene Based Non-fullerene Small Molecular Acceptors for Polymer Solar Cell Application

摘要： Two novel non-fullerene small molecule acceptors were prepared with the conjugated backbone of 5H- fluoreno[3, 2- b:6, 7- b’] dithiophene carrying the electron deficient unit of dicyanomethylene indanone (DICTFDT) and rhodanine (TFDTBR), respectively. The two acceptors exhibited excellent thermal stability and strong absorption in the visible region. The LUMO level is estimated to be at -3.89 eV for DICTFDT and -3.77 eV for TFDTBR. When utilized as the acceptor in bulk heterojunction polymer solar cells with the polymer donor of PBT7-Th, the optimized maximum power conversion efficiency of 5.12% and 3.95% was obtained for the device with DICTFDT and TFDTBR, respectively. The research demonstrates that 5H- fluoreno[3, 2- b:6, 7- b’] dithiophene can be an appealing candidate for constructing small molecular electron acceptor towards efficient polymer:non-fullerene bulk heterojunction solar cells.

Simultaneous enhanced efficiency and thermal stability in organic solar cells from a polymer acceptor additive

摘要： The thermal stability of organic solar cells is critical for practical applications of this emerging technology. Thus, effective approaches and strategies need to be found to alleviate their inherent thermal instability. Here, we show a polymer acceptor-doping general strategy and report a thermally stable bulk heterojunction photovoltaic system, which exhibits an improved power conversion efficiency of 15.10%. Supported by statistical analyses of device degradation data, and morphological characteristics and physical mechanisms study, this polymer-doping blend shows a longer lifetime, nearly keeping its efficiency (t = 800 h) under accelerated aging tests at 150 oC. Further analysis of the degradation behaviors indicates a bright future of this system in outer space applications. Notably, the use of polymer acceptor as a dual function additive in the other four photovoltaic systems was also confirmed, demonstrating the good generality of this polymer-doping strategy.