New semi-crystalline photovoltaic polymers were synthesized and the optimized device exhibited 9.39% efficiency in a ∼300 nm thick single-cell device.

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We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles.

Percolation networks of silver nanowires (AgNWs) are commonly used as transparent conductive electrodes (TCEs) for a variety of optoelectronic applications, but there have been no attempts to precisely control the percolation networks of AgNWs that critically affect the performances of TCEs. Here, we introduce a capillary printing technique to precisely control the NW alignment and the percolation behavior of AgNW networks. Notably, partially aligned AgNW networks exhibit a greatly lower percolation threshold, which leads to the substantial improvement of optical transmittance (96.7%) at a similar sheet resistance (19.5 Ω sq(-1)) as compared to random AgNW networks (92.9%, 20 Ω sq(-1)). Polymer light-emitting diodes (PLEDs) using aligned AgNW electrodes show a 30% enhanced maximum luminance (33068 cd m(-2)) compared to that with random AgNWs and a high luminance efficiency (14.25 cd A(-1)), which is the highest value reported so far using indium-free transparent electrodes for fluorescent PLEDs. In addition, polymer solar cells (PSCs) using aligned AgNW electrodes exhibit a power conversion efficiency (PCE) of 8.57%, the highest value ever reported to date for PSCs using AgNW electrodes.

absorption spectra extending to the NIR region have been designed and applied to the fabrication of OSCs. [6][7][8] A critical challenge arises as one decreases optical bandgaps (E g opt ) with respect to simultaneously achieving a high external quantum efficiency (EQE) and high open-circuit voltage (V OC ). [9] This challenge is due to the counterbalance between the driving force for charge separation, which aids in photocurrent generation, and voltage loss in the cell. [10,11] Finding ways to maximize V OC requires one to reduce the energy loss (E loss = E g opt -eV OC ) that occurs as a result of the multiple states that follow exciton generation. [12] Narrow bandgap (NBG) non-fullerene acceptors (NFAs) have emerged as the next generation of electron acceptors in OSCs. [13][14][15][16][17][18] Tunability of E g opt through molecular design allows one to tailor NIR absorption characteristics. [19,20] Considering that the maximum human photopic sensitivity is 555 nm and the maximum human scotopic sensitivity is 507 nm, [21] transparent photoactive materials should predominantly absorb solar radiation from ≈650 nm into the NIR region for semitransparent solar cell applications. In addition, since ≈50% of solar radiation intensity is in the NIR region, the development of NBG-NFAs with E g opt below ≈1.35 eV is desirable to effectively harvest solar NIR radiation. [1] Another encouraging feature of NFAs is that the energetic offsets that drive charge generation are small (<0.3 eV), [18,[22][23][24] which is beneficial for maintaining low E loss . Despite these desirable features, there has been less consideration for designing NBG-NFAs for transparent/NIR absorbing OSC applications. To address this challenge and expand the design of NIR harvesting acceptor molecules, we demonstrate in this contribution a new molecular design for ultra NBG-NFA materials with strong NIR response and small E loss .The two NBG NFAs described in this contribution are COTIC-4F and SiOTIC-4F (Figure 1a). Their molecular design includes incorporation of a cyclopentadithiophene (CPDT), or dithienosilole (DTS), unit as the central donor (D) fragment, which is flanked by two alkoxythienyl units (D′) to form an electron-rich D′-D-D′ central core. The D′-D-D′ units are end-capped with Two narrow bandgap non-fullerene acceptors (NBG-NFAs), namely, COTIC-4F and SiOTIC-4F, are designed and synthesized for the fabrication of efficient near-infrared organic solar cells (OSCs). The chemical structures of the NBG-NFAs contain a D′-D-D′ electron-rich internal core based on a cyclopentadithiophene (or dithienosilole) (D) and alkoxythienyl (D′) core, end-capped with the highly electron-deficient unit 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (A), ultimately providing a A-D′-D-D′-A molecularconfiguration that enhances the intramolecular charge transfer characteristics of the excited states. One can thereby reduce the optical bandgap (E g opt ) to as low as ≈1.10 eV, one of the smallest values for NFAs reported to date. In bulk-he...

Open‐circuit voltage (VOC) losses in organic photovoltaics (OPVs) inhibit devices from reaching VOC values comparable to the bandgap of the donor–acceptor blend. Specifically, nonradiative recombination losses (∆Vnr) are much greater in OPVs than in silicon or perovskite solar cells, yet the origins of this are not fully understood. To understand what makes a system have high or low loss, an investigation of the nonradiative recombination losses in a total of nine blend systems is carried out. An apparent relationship is observed between the relative domain purity of six blends and the degree of nonradiative recombination loss, where films exhibiting relatively less pure domains show lower ∆Vnr than films with higher domain purity. Additionally, it is shown that when paired with a fullerene acceptor, polymer donors which have bulky backbone units to inhibit close π–π stacking exhibit lower nonradiative recombination losses than in blends where the polymer can pack more closely. This work reports a strategy that ensures ∆Vnr can be measured accurately and reports key observations on the relationship between ∆Vnr and properties of the donor/acceptor interface.

A series of narrow bandgap electron acceptors was designed and synthesized for efficient nearinfrared (NIR) organic solar cells. Extending π-conjugation of donor frameworks led to an intense intramolecular charge transfer, resulting in broad absorption profiles with band edge reaching 950 nm. When blended with an electron donor polymer PTB7-Th, IOTIC-2F exhibits efficient charge transfer even with a small energetic offset, so as to achieve a large photogenerated current over 22 mA cm −2 with small energy losses (~0.49 eV) in solar cell devices. With an intense NIR absorbance, PTB7-Th:IOTIC-2F-based cells achieve a power conversion efficiency (PCE) of 12.1% with good visible transparency (52% transmittance from 370 -740 nm). Analysis of film morphology reveals that processing with solvent additives enhances crystalline features of acceptor components, while keeping an appropriate level of donor:acceptor intermixing in the binary blends. The incorporation of the third component, ITIC-2F, into the PTB7-Th:IOTIC-2F blends increases the device efficiency up to 12.9%. The improvement is assigned to the cascaded energy-level structure and desirable nanoscale phase separation of the ternary blends, which is beneficial to the photocurrent generation. This work provides an efficient molecular design strategy to optimize non-fullerene acceptor properties for efficient NIR organic photovoltaics.

We present an investigation of polymer light-emitting diodes (PLEDs) with a solution-processable graphene oxide (GO) interlayer. The GO layer with a wide band gap blocks electron transport from an emissive polymer to an ITO anode while reducing the exciton quenching between the GO and the active layer in place of poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS). This GO interlayer maximizes hole-electron recombinations within the emissive layer, finally enhancing device performance and efficiency levels in PLEDs. It was found that the thickness of the GO layer is an important factor in device performance. PLEDs with a 4.3 nm thick GO interlayer are superior to both those with PEDOT:PSS layers as well as those with rGO, showing maximum luminance of 39 000 Cd/m(2), maximum luminous efficiencies of 19.1 Cd/A (at 6.8 V), and maximum power efficiency as high as 11.0 lm/W (at 4.4 V). This indicates that PLEDs with a GO layer show a 220% increase in their luminous efficiency and 280% increase in their power conversion efficiency compared to PLEDs with PEDOT:PSS.