wangzhaowei

A universal strategy for efficient light trapping through the incorporation of gold nanorods on the electron transport layer (rear) of organic photovoltaic devices is demonstrated. Utilizing the photons that are transmitted through the active layer of a bulk heterojunction photovoltaic device and would otherwise be lost, a significant enhancement in power conversion efficiency (PCE) of poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]:phenyl-C₇₁-butyric acid methyl ester (PCDTBT:PC₇₁BM) and poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophenediyl]] (PTB7):PC₇₁BM by ≈13% and ≈8%, respectively. PCEs over 8% are reported for devices based on the PTB7:PC₇₁BM blend. A comprehensive optical and electrical characterization of our devices to clarify the influence of gold nanorods on exciton generation, dissociation, charge recombination, and transport inside the thin film devices is performed. By correlating the experimental data with detailed numerical simulations, the near-field and far-field scattering effects are separated of gold nanorods (Au NRs), and confidently attribute part of the performance enhancement to the enhanced absorption caused by backscattering. While, a secondary contribution from the Au NRs that partially protrude inside the active layer and exhibit strong near-fields due to localized surface plasmon resonance effects is also observed but is minor in magnitude. Furthermore, another important contribution to the enhanced performance is electrical in nature and comes from the increased charge collection probability.

High efficiency organic photovoltaic (OPV) devices are fabricated based a novel and universal light trapping mechanism, using gold nanorods (Au NRs) as back contact reflectors. The incorporation of Au NRs inside the back contact interfacial layer (titanium sub oxide) gives rise to a device efficiency of ≈13%, compared to the record performance of 8.25%. This is revealed to be mainly due to scattering by a combination of theoretical and experimental results.

In article 1500877, Thuc-Quyen Nguyen, Harald Ade, and co-workers demonstrate the connection between device performance and morphological parameters in organic photovoltaics. The results demonstrate the complex correlation between domain purity, size, and molecular ordering, and highlight the requirement of achieving sufficient average phase purity of donor and acceptor domains to diminish charge recombination losses in solution-processed small-molecule bulk heterojunction solar cells.

In article number 1500761, Jongseung Yoon and co-workers report a photovoltaic system that can improve the collection efficiency of above-bandgap, long-wavelength photons in ultrathin nanostructured silicon solar cells. A flexible composite solar module integrated with silver nanostructures and upconversion printing medium enables the enhanced photovoltaic performance of surface-embedded 8-μm-thick silicon microcells via synergistic contributions from plasmonically amplified spectral upconversion, waveguiding, and fluorescence of the upconversion medium.

In article number 1501070, Edgardo Saucedo and co-workers report a breakthrough in kesterite-based technologies, demonstrating that high-voltage and high-efficiency devices can be easily achieved using an innovative approach based on the introduction of a superficial Ge nanolayer, leading to efficiencies exceeding 10%. To illustrate this, the image shows how materials management at nanoscale level can have a strong impact on the macroscopic properties of photovoltaic devices.