Dye-sensitized solar cells based on bacterial-based photosensitizers (bio-sensitized DSSCs) are promising bio-photoelectronic molecular devices exhibiting enhanced electron excitation, injection, and dye regeneration for efficient photon-to-electron quantum-conversion. Achieving high DSSCs performance via environmentally sustainable, cost-effective, and naturally-sensitized plant-based or bacterial-based biomolecules remains a challenge. Here, we provide a comprehensive study on the mechanisms involved in the utilization of biomolecular bacterial-based pigments (e.g. proteins and carotenoids) for an improved bio-sensitized DSSCs performance. Protein complexes and chlorophyll a/carotenoids are among many bio-photosensitizers demonstrating high incident photon-to-current efficiency (IPCE). Pigments molecular structure, donor-π-acceptor conjugation, and anchoring groups have been discussed and attributed to theoretical dye HOMO–LUMO bandgaps and their corresponding bio-sensitized DSSCs IPCE. This review provides critical understanding of advancements towards natural photosensitization: (i) carboxyl/hydroxyl groups attached to acceptor segments provide firm attachment and rapid electron injection, (ii) proteins/carotenoids hybrid dyes induce visible-light photosensitivity and broaden absorbance, (iii) increased conjugated π -bonds (n > 13) develop pigment visible-NIR absorption with intensified photoactivity, (iv) chromatophores integrated with bio-electrolyte provide a unidirectional flow of electrons, (v) reaction center (RC)-sensitized DSSCs have better optoelectronic properties than light-harvesting complex (LH2) due to its efficient charge separation, (vi) antioxidants hinder degradation of pigmented-photoanodes from UV radiation, (vii) solid-state redox improves device stability and dye neutralization; which all together would boost the dye sensitization performance in bio-sensitized DSSCs. The highest recorded IPCEs are found for TiO2-based DSSCs using plant-based coumarin (9%) and from [A. amentacea + P. pterocarpum] pigments (8.22%). Futuristically, we anticipate that these biologically-derived photosensitizers can be integrated into photoanodes for photoelectronic applications including DSSCs, multi-junction cells, photodiodes, phototransistors, photodetectors, flexible bioelectronic films and clothes, bio-LEDs, and photo-tunneling junctions.

Biomolecular photosensitizers for dye-sensitized solar cells: Recent developments and critical insights

Considering increasing energy demands, it is still a challenge to find finite resources of alternative energy. Owing to their wide range of applications, transparency, simple structure, and low cost, dye-sensitized solar cells (DSSCs) have been extensively studied as one of the most promising new generation silicon-based solar cells. During last decade, tremendous research efforts have been invested to improve the efficiency of solar energy conversion of DSSCs. In this review, we overview various strategies that lead to better performance and stability of the fabricated cell. Recent challenges associated with nanostructured electrodes, device layer structure design, types of dyes and electrolytes with DSSCs performance were studied and discussed.

Performance improvement of modified dye-sensitized solar cells

Callindra haematocephata and Peltophorum pterocarpum flowers as natural sensitizers for TiO2 thin film based dye-sensitized solar cells

Recent advances in hybrid solar cells based on natural dye extracts from Indian plant pigment as sensitizers

Studies on the optical and photoelectric properties of anthocyanin and chlorophyll as natural co-sensitizers in dye sensitized solar cell

Celulas solares sensibilizadas por corantes (DSSCs) foram fabricadas usando corantes naturais extraidos das flores de Amaranthus caudatus, Bougainvillea spectabilis, Delonix regia, Nerium oleander, Spathodea companulata e uma mistura de extratos. O desempenho da celula fotoeletroquimica (PEC) DSSCs desses corantes mostrou um fator de preenchimento (FF) geralmente maior que 50%, a voltagem de circuito aberto (VOC) variou de 0,45 a 0,55 V, e as densidades de fotocorrente de circuito curto (JSC) ficaram na faixa de 0,013 a 1,82 mA cm−2. A alta voltagem de circuito aberto (VOC = 0,55 V) e a densidade de fotocorrente de circuito curto (JSC = 1,82 mA cm−2) foram obtidas a partir de DSSC sensibilizada por extrato etanoico da flor de Amaranthus caudatus. A eficiencia de conversao de energia (η) da DSSC com extrato etanoico da flor Amaranthus caudatus atingiu 0,61%. O desempenho da PEC DSSC com solucoes de corantes misturados tambem foi investigado. No entanto, extratos misturados nao apresentaram sinergia na fotosensibilizacao quando comparados aos extratos individuais. A celula sensibilizada somente pelo extrato etanoico da flor Amaranthus caudatus apresentou o melhor desempenho. Os dispositivos mostraram que a eficiencia de conversao foton-corrente monocromatica incidente (IPCE) variou de 4,7% a 52%. Os resultados dos dados de IPCE sao consistentes com as curvas J-V.

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Dye Sensitized Solar Cells Using Natural Pigments from Five Plants and Quasi-Solid State Electrolyte

The large-scale production of high-quality graphene is the major focus of scientists and engineers recently. However, its massive manufacturing routes from its precursor graphene oxide (GO) are involved in the production of toxic gasses and consist of hazardous explosive steps that severely hurt and threaten ecological balance and human health. Therefore, in this study, we investigated the green, effective, and economical approach for the synthesis of graphene by using Vernonia amygdalina (VA) plant leaf extracts for the effective and efficient reduction of GO. The nonexplosive two-step synthesis of GO in a short period of time in the absence of an ice bath was used in this study. The appropriate solvent for the extraction of VA for the green synthesis of graphene was methanol, and the reducing and capping agent in the plant extract was identified to be terpenoids and polyphenols. The graphene/rGO obtained this way was characterized by UV-VIS, XRD, FTIR, SEM, HR-TEM, and EDAX that confirmed the successful reduction of GO to graphene under the hydrothermal process. The HR-TEM images showed the development of few layers of graphene. The FTIR result also shows the complete reduction of GO. Hence, methanol extracted VA leaves consisted of the most appropriate compounds for reducing and capping agent in the green synthesis and could be the preferred method for the large-scale production of graphene-based materials.

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A Novel and Simplest Green Synthesis Method of Reduced Graphene Oxide Using Methanol Extracted Vernonia Amygdalina: Large-Scale Production

Today, the issue of the environment is the concern of scientists worldwide. Aside from developed countries, developing countries are revolutionizing their economy from agriculture to industries, ag...

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Enhanced Photocatalytic Activity of Reduced Graphene Oxide/Bismuth Sulfide Nanostructure Composites for the Degradation of Methylene Blue

The deterioration of the quality of groundwater by fluoride is the cause of shortage of drinking water supply in the rift valley region. Most people living in the rural areas are using groundwater as the source of their potable water; however, it is contaminated with high concentrations of fluoride ion above the permissible level. Hence, this study was designed to investigate the adsorption of fluoride from groundwater by graphene oxide (GO) under specific conditions, such as: agitation rate of 120 rpm, contact time of 90 minutes, adsorbent dosage of 0.42 mg/L, initial fluoride concentration of 10 mg/L, and pH of 6.8. The result obtained showed 99.3% fluoride removal from the NaF prepared solution and 91.6% fluoride removal from the real sample. The retained properties of GO after adsorption observed on UV–Vis analysis confirmed that the adsorbent can be recyclable. The result obtained also showed that the adsorption kinetics with the coefficient of determination (R2) for pseudo-second order (SSO) and pseudo-first order (SFO) were 0.99 and 0.96, respectively. Based on these results, the adsorption of fluoride onto GO is a pseudo-second-order kinetics type. According to the result, the Freundlich isotherm model showed a good fit to the experiment with R2 (0.99). The adsorption capacity of the adsorbent was found to be 301.43 mg/g. Hence, this study showed that GO is the preferred adsorbent for the removal of fluoride from groundwater.

Graphene Oxide Nanoadsorbent for the Removal of Fluoride Ion from Groundwater: Adsorbent Performance and Adsorption Mechanism

In this work, the effect of DIM on the PCE and photostability of PCDTBT:PC71BM PSCs was investigated. DIM is an effective additive in a BHJ PCDTBT:PC71BM solar cell since it fulfills the requirement of a selective PC71BM dissolution. PCE of the device based on PCDTBT:PC71BM processed with DIM is higher than that of the reference device. In terms of the device stability, the PSCs processed with DIM showed poor stability at longer light exposure time. For the device without DIM especially as the light exposure time was increased, the device stability was better because the PCDTBT could be shielded from air by an aggregated PC71BM layer. For the PCDTBT:PC71BM device processed with DIM, the results obtained from measurement indicates that it has a lower recombination rate. The result from IS measurement shows that for pristine PCDTBT:PC71BM devices with 3% DIM, the active layer resistance is lower compared to the device without DIM. However, after irradiating the device for 5 hr, the resistance of the device processed with DIM is higher and it is consistent with decreased PCE of the aged device.

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Teketel Yohannes Anshebo

Papers

Dye Sensitized Solar Cells Using Natural Pigments from Five Plants and Quasi-Solid State Electrolyte

A Novel and Simplest Green Synthesis Method of Reduced Graphene Oxide Using Methanol Extracted Vernonia Amygdalina: Large-Scale Production

Enhanced Photocatalytic Activity of Reduced Graphene Oxide/Bismuth Sulfide Nanostructure Composites for the Degradation of Methylene Blue

Graphene Oxide Nanoadsorbent for the Removal of Fluoride Ion from Groundwater: Adsorbent Performance and Adsorption Mechanism

Investigation on the Effects of Additive on Performance and Photostability of PCDTBT:PC71BM Solar Cells