Organic photovoltaic cells (OPVs) are a promising cost-effective alternative to silicon-based solar cells, and possess light-weight, low-cost, and flexibility advantages. Significant progress has been achieved in the development of novel photovoltaic materials and device structures in the last decade. Nowadays small molecular semiconductors for OPVs have attracted considerable attention, due to their advantages over their polymer counterparts, including well-defined molecular structure, definite molecular weight, and high purity without batch to batch variations. The highest power conversion efficiencies of OPVs based on small molecular donor/fullerene acceptors or polymeric donor/fullerene acceptors are up to 6.7% and 8.3%, respectively, and meanwhile nonfullerene acceptors have also exhibited some promising results. In this review we summarize the developments in small molecular donors, acceptors (fullerene derivatives and nonfullerene molecules), and donor–acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs. We focus on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances. This structure–property relationship analysis may guide rational structural design and evaluation of photovoltaic materials (253 references).

Small molecule semiconductors for high-efficiency organic photovoltaics

Power consumption is forecast by the International Technology Roadmap of Semiconductors (ITRS) to pose long-term technical challenges for the semiconductor industry. The purpose of this paper is threefold: (1) to provide an overview of strategies for powering MEMS via non-regenerative and regenerative power supplies; (2) to review the fundamentals of piezoelectric energy harvesting, along with recent advancements, and (3) to discuss future trends and applications for piezoelectric energy harvesting technology. The paper concludes with a discussion of research needs that are critical for the enhancement of piezoelectric energy harvesting devices.

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Powering MEMS portable devices—a review of non-regenerative and regenerative power supply systems with special emphasis on piezoelectric energy harvesting systems

The processing characteristics of organic semiconductors make them potentially useful for electronic applications where low-cost, large area coverage and structural flexibility are required. This critical review gives a general introduction about the current standing in the area of OFETs focusing on the new processable small molecules that have been recently reported for their use as organic semiconductors. A general description of the OFETs device operation and the transport mechanisms that dominate organic semiconductors is provided, followed by an overview of the strategies and materials employed to fabricate p-type, n-type and ambipolar OFETs. Some new tendencies and applications that are currently being developed employing OFETs are also described, such as the preparation of electronic paper, sensors or light emitting transistors (85 references).

Novel small molecules for organic field-effect transistors: towards processability and high performance

This critical review discusses specific chemical and physicochemical requirements which must be met for organic compounds to be considered as promising materials for applications in organic electronics. Although emphasis is put on molecules and macromolecules suitable for fabrication of field effect transistors (FETs), a large fraction of the discussed compounds can also be applied in other organic or hybrid (organic–inorganic) electronic devices such as photodiodes, light emitting diodes, photovoltaic cells, etc. It should be of interest to chemists, physicists, material scientists and electrical engineers working in the domain of organic electronics (423 references).

Electroactive materials for organic electronics: preparation strategies, structural aspects and characterization techniques

Heterojunction organic photovoltaics have been the subject of intensive academic interest over the past two decades, and significant commercial efforts have been directed towards this area with the vision of developing the next generation of low-cost solar cells. Materials development has played a vital role in the dramatic improvement of organic solar cell performance in recent years, and this is driven primarily by the advancement of p-type semiconductors as donor materials. With the highest performing solar cells today dominated by acceptors based on members of the fullerene family, much less attention has been devoted to other classes of n-type acceptors. In this review, we will provide an overview of the progress in the synthesis, characterization and implementation of the various classes of non-fullerene-based n-type organic acceptors for photovoltaic applications.

Organic non-fullerene acceptors for organic photovoltaics

Soluble derivatives of perylene and naphthalene diimide for n-channel organic field-effect transistors

We have fabricated heterojunction solar cells comprising active layers of perylene diimide (PDI) or perylene bisbenzimidazole (CONPER, conjugated perylene dye) as electron acceptor and ZnPC as donor. Bilayer solar cells were produced by successive evaporation of zinc phthalocyanine (ZnPC) and perylene diimide (PDI) or perylene bisbenzimidazole (CONPER) on glass substrates coated with indium doped tin oxide. Active layers with different thickness were evaporated. The bilayer cells were characterized under simulated AM 1.5 illumination (100 mW/cm 2 ). The best results were obtained for the device structure of ITO/PEDOT/ZnPC (40 nm)/perylene bisbenzimidazole (60 nm)/Al (70 nm).

Donor-acceptor heterojunction solar cells based on perylene dimide and perylene bisbenzimidazole

We report the characterization of 1,8-naphthalene benzimidazole comprising carboxyl group. We have fabricated dye-sensitized nanocrystalline TiO 2 solar cell (DSSC) based on naphthalene benzimidazole dye. The device structure is FTO/nc-TiO 2 /Dye/I – /I 3 – /Pt/ FTO. We calculated the E HOMO and E LUMO levels of this new dye by using cyclic voltammetry measurement. The E LUMO level of naphthalene benzimidazole is 3.2 eV. This value is higher than the conduction band of TiO 2 . Electrons can be injected to the conduction band of TiO 2 . The current-voltage ( I - V ) characteristic of cell was measured under simulated AM 1.5 illumination (100 mW/cm 2 ). We obtained the open circuit voltage; V oc = 0.344 V, short circuit current density; I sc = 5.93 mA cm -2 , filling factor; FF = 0.45 , power conversion efficiency; η = 0.91%.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/C6DC9A4E0249BFF0EC87522640B131A1/S1286004207000869a.pdf/div-class-title-dye-sensitized-solar-cell-based-on-1-8-naphthalene-benzimidazole-comprising-carboxyl-group-a-href-fn1-ref-type-fn-a-div.pdf

Dye sensitized solar cell based on 1,8-naphthalene benzimidazole comprising carboxyl group

İklim değişikliği ve çevre kirliliği günümüzde insanlığın karşılaştığı en önemli sorunlar arasında yer almaktadır. Enerji sistemlerinde kullanılan soğutucu akışkanların seçimi ve çevre dostu soğutucu akışkanların kullanımının önemi gün geçtikçe artmaktadır. Düşük küresel ısınma potansiyeline (KIP) ve ozon delme potansiyeline (ODP) sahip soğutucu akışkan seçimi çevre duyarlılığı açısından araştırmacılara önemli bir misyon yüklemektedir. 
Bu çalışmada, hidrokarbon soğutucu akışkan propan (R290) kullanılarak tasarlanmış bir ısı pompası sisteminin verimlilik analizi gerçekleştirilmiştir. Geleneksel ısı pompalarından farklı olarak tasarlanan bu sistemde; ısı geri kazanımı yapılarak, hem gerektiğinde kompresör çıkışındaki yüksek sıcaklıktaki soğutkanın hem de kondenser çıkışındaki soğutucu akışkanın ısısının depolanması ile bu durumlardaki verimlilik analizleri yapılmıştır. Yapılan analizlerde, ısı pompasının performans katsayısı (COP) değeri 2,75 olarak hesaplanmıştır. Geliştirilen modelde, defrost sürecince harcanan enerji miktarı elektrikli ısıtıcılı defrost yöntemine göre %63,6 oranında azaltılmıştır. Sistemin güneş enerjisinden de yararlanılarak daha da veriminin artırılabileceği öngörülmüştür.

Design of an Air Source Heat Pump System Having High Defrost Efficiency and Natural Refrigerant

In this study, open-type refrigeration cabinets were designed and manufactured using hot gas and electrical resistance defrost methods and R290, R449A and R404A refrigerants. The aim of this study is to determine the temperature increase of the products during the process, CO2 emission amount, defrost efficiency, and energy efficiency index (EEI) value with different defrost methods and refrigerants for commercial refrigeration systems. The increase in package temperatures during the defrosting process was determined as 1.33 °C in the electrical method. The results showed that the hot gas method was 7.15% more efficient in terms of defrosting efficiency. The EEI value was calculated as 78.76 with the use of R290 in the hot gas method and the energy class was determined as F and the hot gas emit 5.9% less CO2 than in the resistance experiments. In the hot gas defrost method, it was seen that 20.3% less energy was consumed compared to the total consumption. It was observed that R290 refrigerant and the hot gas defrost method were the most suitable for commercial systems in terms of defrosting process losses, total energy consumption, and temperature rise of the cooled product during defrosting.

S. Erten

Papers

Soluble derivatives of perylene and naphthalene diimide for n-channel organic field-effect transistors

Donor-acceptor heterojunction solar cells based on perylene dimide and perylene bisbenzimidazole

Dye sensitized solar cell based on 1,8-naphthalene benzimidazole comprising carboxyl group

Design of an Air Source Heat Pump System Having High Defrost Efficiency and Natural Refrigerant

Determination of defrost efficiency and energy efficiency index value using different defrost methods and refrigerants: An experimental study