Introduction
Alternative renewable energy continues to grow popularity because of the upsetting climate change caused by greenhouse gases, exhaustion of non-renewable energy resources and rising global demand for energy. Renewable resources of electricity production are vital progress and are fundamentally motivated by cost.
Solar energy is clean and profuse that is why it is the best among the available substitutes. The modern solid-state photovoltaic (PV) technology began in 1954 upon the discovery of silicon (Si) diodes photovoltaic effect . Crystalline Si and a wide range of thin film solar cells, which are inorganic, are the prevailing photovoltaic technologies employed nowadays .
The amount of solar energy hitting the earth’s surface in an hour is calculated to be equivalent to the energy consumption of every human in a year. Solar active technology include the direct conversion of sunlight into electricity using PV cells, solar thermal collectors for heating and cooling (SHC) and concentrating solar power (CSP).
Currently, Photovoltaic (PV) offers 0.1% of whole worldwide electricity production. The technology of PV is growing very fast as a result of efficient sustaining strategies and latest vivid cost diminution. It is a commercially accessible and dependable technology with a noteworthy prospective for long-standing development in practically every region in the Earth. The PV is predicted to supply five percent of worldwide electrical energy expenditure in the year 2030, getting higher to eleven percent in 2050.
Photovoltaic technology is the electricity generation through the photon illumination of semiconductors . It is considered to be one of the most sustainable in terms of effectiveness; and a good electrical generation technology in the planet. Photovoltaic (PV) has a noteworthy prospective amongst the unconventional energy generation because of the solar energy renewability, source of electricity and the PV-material portability . The total yearly solar energy received by the Earth’s surface is 63 x10!" watts and this is more than the collective energy requirement of the Earth’s population .
Several methods of generating solar fuels are being studied and they all present coupled advantages and limitations. Some of the solar fuels generators are recognized as photo-electrochemical cells. However, these generators work through different physical principles. An artificial photosynthetic process is a course where the solar energy is collected and accumulated within the fuel’s chemical bonds. The research in artificial photosynthetic process has lately gone through fast development because of the guarantee brought by generators of scalable solar fuels. This research would likely supply a carbon energy source that is competent of answering alarms regarding the effect of carbon discharge on our climate at the same time, providing a secured energy and environment.
There are existing studies that focus on the development of various set of proposals for solar fuels generators; however, every one of which pose distinct challenges coupled with the development and investigation necessary to achieve a complete equipped structure. In addition, the growth of the research realized in variety of designs differs extensively. Notwithstanding these dissimilarities, a selection of solar fuels generators are frequently classified jointly and termed as photoelectrochemical cells.
This paper presents a discussion of solar energy focusing on photovoltage technology. The paper includes the details of main advantages, disadvantages and limitations of the solar source, the current state of technological development of the solar source, the future challenges in developing solar energy, and the role of solar source in the future of energy as well as its interaction with other energy technologies.
Main advantages, disadvantages and limitations of the Solar Power (Photovoltaic Technology)
Photovoltaic, although they do not have moving parts and have low working costs, have high installation overheads. Photovoltaic source is fundamentally endless and extremely enormous but a comparatively less dense energy. A module can be set up at practically all point-of-use except that it is short of prevalent commercially obtainable structure assimilation and mechanism. A module can last more than twenty years with superior dependability in modules but inferior dependability of supplementary components, like the battery for solutions of non-grids.
Some of the advantages of PV are the high reported efficiencies of conversion of solar to fuel energy. PV is also independent of the power-producing connection in reference to the official latent for the wanted reactions (Nielander et al.,2014). For economic and environmental viewpoint, photovoltaic has no combustion that is beneficial to pollution and climate change, no discharges for the duration of operation. For safety issues, it operates in ambient temperature that can prevent corrosion due to high temperature .
The disadvantages and limitations related with PV-based cells comprise accomplishing a cost improvement for building electrolyte and catalysts interfaces that are steady, conductive and transparent under fuel structuring operational setting, forming a scheme that use a separate photovoltaic cell in dry setting connected to a distinct fuel-forming apparatus and making a structure with the electrolyte-immersed operational photovoltaic cell.
Further research is required for the electrodes stabilization using materials that serve as conductive and transparent defensive layers, the integration of components, detection of resources, maturity of low-cost manufacturing techniques and the building up of a photovoltaic cells that is cost competitive (Nielander et al., 2014).
The inorganic solar cells cost limits their extensive approval and recognition; for this reason, solar PV reports in US are only less than 0.1 % energy production. Technology uses organic materials and they are termed as OPVs as an answer for PV’s cost effectiveness. In previous decades, the efficiency of a single junction cell has been doubled. It was from 4% (in 2005) and was raised to about 8-9% by the utilization of the solar cell technology of bulk hetero-junction (BHJ) polymer. The power conversion efficiency of the single junction solar cells using organic materials is projected to be around ten to twelve percent by optimizing bad gap, carrier mobility, energy level and suitable materials.
Photocurrent, fill-factor and photo-voltage balance is necessary to attain elevated power conversion efficiency. In crystalline inorganic semi-conductors, molecules are bonded by weak intermolecular van de Waals interactions and not by covalent bonds. A hopping process transports the charges in semiconductors made of organic materials. The limitation of OPV includes the carrier mobility even though the coefficient for absorption in their types of materials is high. The mobility of carriers limits the thickness of the film that can result to shortage of absorbing photons (Youa et al., 2013).
In terms of PEC or photoelectrochemical cells, they are advantageous in the sense that their constructions are simple and the electrolyte junctions or polycrystalline semiconductor/ are not costly. PEC performance is comparable to the performance of matching single crystalline cells. On the other hand, PEC challenges involve attaining the appropriate mixture of materials to make them stable for operation. They also need to have a suitable band gaps, integration and development of electro-catalysts into the electrolyte or semiconductor junction and proper interfacial energetic. The PEC technology of solar fuel production requires development in semiconducting materials that possess both the proper band gaps for effective sunlight absorption and well-positioned band energetic.
Thus, the key research needs for solar fuels generators based on PEC cells involve the discovery and development of, and the development of methods for incorporating efficient electrocatalysts into semiconductor/ electrolyte interfaces that are stable under operational, fuel-forming conditions (Nielander et al., 2014).
The primary loss for single junction solar cells mechanism is the photovoltage loss brought by the hot carriers thermalization formed when energy of photons is higher than the band absorbed gap. To overcome the limitation of single junction photo-voltaics, tandem solar cells can be used. This mechanism involves more than two single cells that absorbs corresponding wavelength with stacked ranges. This method allows the photon utilization efficiency to improve. Moreover, the losses due to thermalization are reduced through the employment of materials with diverse band gaps.
Using the two cell tandem configuration, we can achieve a fifteen percent effectiveness of polymer tandem solar cells. This percentage depends on the theory that a steady, sixty-five percent, external quantum efficiency (EQE) for the cells in tandem are absorbed inside the spectral range.
For actual application, it is helpful for the utilization of the tandem method to possess two sub-cells that has reduced absorption overlap. This method can make the optimization procedure simpler for the tandem arrangement. The design for tandem polymer solar cell is materialized with the use of the selection between PC71BM and PC61BM because they have distinct coefficient for extinction influenced by their molecular symmetry structure. Some reviews on tandem technology offer complete data for various tandem and structure mechanism. The tandem polymer solar cell evaluation focuses on the materials problems for the interfacial materials, sub-cell interconnection and active layer materials (Youa et al., 2013).
Current state of technological development of the Solar Power
(Photovoltaic Technology)
Photovoltaic cells, PV that generates electricity are called solar electric cells. On the other hand, the PV cells that create fuels are called PV-biased electrosynthetic cells. The buried junctions of these kinds can have an electrical series arrangement using a submerged electrocatalyst in electrolyte. Physical contact between PV electrodes and electrocatalyst is not required. The structure that generates all systems like the photovoltage is self-governing in terms of the nature of the electrolyte or electrocatalyst interface. Examples of electrosynthetic cells that are PV-biased are n-In/SiOx/Si-arrangements base on doped tin oxide ITO, triple-junction arrangements derived from CuInGaSe2, triple-junction of amorphous hydrogenated Si (a-Si:H) and tandem arrangement of AlGaAs/Si (Nielander et al., 2014).
The photocurrent and the photovoltage generated with illumination are utilized in the buried junction device. It is operated by charge disconnection interceded through the electrochemical potential difference or through charge-transfer kinetics difference that occurs in two unlike solids that are in mutual electrical contact.
Measurements of the PV’s voltage-photocurrent characteristics are performed separately. They are utilized to predict performances accurately in solar fuel production. The character of electrolyte and solid interfaces in the scheme of voltage behavior versus photocurrent is independent. When both terminals of the PVs connected to electrocatalysts and the components of the scheme are integrated, they produce similar behavior of voltage-photocurrent relationship. There are reports that state the current working principles behind the photovoltaic electrodes associated with PV cells for the production of both fuel and electricity (Nielander et al., 2014).
Photoelectrochemical PEC cells are devices that use solid/ionic-conductor junctions or solid/electrolyte junctions. This is another basic and particular method of effective charge cariers separation utilizing solid/ionic conductor junction. Semiconductors are the common solid in a PEC cell, and they can be attached to photosensitizer. Examples of solids that are investigated to generate photovoltage at a solid/electrolyte boundary are metals like mercury and platinum.
The photocurrent and photovoltage created in the company of light take place in an apparatus employing an electrolyte-solid due to disparities in the electrochemical potentials of the electrolyte and the solid. The asymmetries in the charge-transfer kinetics for holes across the junction and electrons also influenced the generation of photocurrent and photovoltage.
Common three-electrode potentiostatic experimentation determines the photoelectrodes properties regularly by means of a half-cell pattern. This experiment is governed by the principle that the photoelectrode can be integrated into an equipped, two-electrode, complete PEC cell. In PEC-based solar fuels generators, the voltage-photocurrent dimensions are not permitted to be created separately of the desired reaction dissimilar to PV cells (Nielander et al., 2014).
One photoelectrode that possess an electrolyte- semiconductor junction can comprise the PEC cells that make use of a semiconducting electrode in conjunctions with two photoelectrodes having a counter electrode which is in dark phase. Other components that can comprise the PEC cells are a monolithically incorporated mixture of two photoelectrodes inside a single structure that carries out both the cathodic and anodic half-reactions all together .
Regenerative photoelectrochemical cells are PEC cells that generate electricity only. In regenerative PEC, there is regeneration of the species that is oxidized or reduced at the operational photoelectrode at the counter electrode. Theoretically, the reaction yields no net change in the composition of the species solution. Regenerative PEC cells usually controls Dye-sensitized solar cells (DSSCs). An illustration of regenerative PEC cell is the n-Si/CH3OH-1, 10 dimethylferrocene+/0/ITO cell.
Photoelectrosynthetic cells are PEC cells that create fuels at the electrolyte-semiconductor junction. PEC-biased photoelectrosynthetic cell is the result when photoelectrosynthetic PEC cell is combined with a regenerative PEC cell. On the other hand, the product when metallic electrodes are combined with a regenerative PEC cell is the PEC-biased electrosynthetic cell.
Photoelectrochemical cells are utilized to bias both PV and PEC cells to help in fuel configuration similar to photovoltaic cells. DSSC positioned in series with Fe2O3/electrolyte junction cell electrically is PEC-biased photoelectrosynthetic cell for water splitting.
The DSSC is a device with two unconnected terminals. It has independent relationship between photovoltage, photocurrent and fuel formation of desired reaction. DSSC works similar to PEC due to the independence of photovoltage and photocurrent of the solution at the point of DCCS terminals (Nielander et al., 2014).
Photovolaic structures frequently take in either thin film or crystalline silicon technologies. Developed materials are utilized in the thin film technology such as cadmium telluride. Cadmium telluride (CdTe) has had noteworthy accomplishment in solar progress at utility level. The concentrating photovoltaic (CPV) systems previously have expanded traction in the utility level industry.
The concentrating photovoltaic (CPV) systems utilize optic lenses. These lenses are use to concentrate sunlight onto solar cells with high efficiency operation. The CPV system needs direct sunlight for its operation because of the incorporation of lenses. It employs one or two axes trackers in order to tag along the sun athwart the atmosphere.
The CPV technology unites two mechanisms to produce electricity. It uses concentrators and semiconducting materials. The concentrators are mirrors and lenses while the semiconducting materials depend on the selection of accessible PV technology. Producers make use of a mixture of semiconducting material and concentrators to attain the minimum energy cost based on a chosen approach and technique.
There is a possible cost lead of CPV over conventional PV. The cost advantage of CPV can be achieved if the technology makes use of less semiconducting material to form the CPV. Moreover, poorer efficiency CPV technologies can make use of silicon (CIGS and CdTe are also possible to use). The optimum efficiencies are attained by using multi-junction cells with materials excluding silicon. In laboratory level, the efficiency for CPV that does not use silicon can achieve up to forty percent; while in field level, the efficiencies of CPV that does not use silicon as material can reach up to thirty percent above.
The concentration levels in CPV vary from 2x to 500x. This range can be interpreted as two suns to five hundred suns. However, technologies for this study have projected to achieve up to one thousand suns. The concentrations of CPV are classified as high, medium and low. The high temperatures are expected for high sunlight concentration that is why the CPV systems frequently involve incorporation of heat sinks in order to disperse heat and to avoid malfunction of the solar cells.
The CPV technology works in the same way as PV. The two technologies employ inverters for the conversion of the DC to AC produced by the solar cells. After the conversion, the product will be conveyed to electrical grid.
Both PV and CPV systems require lower water supply and land resource compared to solar technologies because of the high power density of both systems. Moreover, the potential of the CPV technology to lessen the cost is high since most of the expenditure is concentrated with lenses, tracking devices and mirrors only. The mentioned materials are highly adaptable economically.
The solar energy technologies are photovoltaic, concentrating Solar Power and solar thermal collector. Photovoltaic include thin film (CIGS, CdTe and amorphous silicon) and mono-crystalline and multi-crystalline. For the concentrating solar cell technology, the dispersed power towers, dish-stirling engines, parabolic trough mirrors and thin-film. The last technology is the solar thermal collectors that include batch solar, evacuated tube collectors and flat plate.
Future challenges in developing Solar Power (Photovoltaic Technology)
Solar technology has been the center of the renewable energy industry and has been a chief source of novel electricity production for the previous few years in European countries. There are a number of reasons why businesses and private sectors search for techniques to control and manage the production of energy. There exists the responsibility of everyone to the environment. On the other hand, the actual problem is extenuating the danger of depending completely upon outside energy suppliers for companies. The industrial and domestic patrons of solar technology choose to invest because the technology allows them to retract power from the providers of energy and to acquire more management over their prospect energy demand for payment.
Although the photovoltaic technology has a growing share of market, some factors limit this technology to develop further. There are several obstacles that confront the technology of solar energy and two of which are in terms of energy market.
There is an elevated height of doubt amongst possible clientele for this technology. Moreover, there is a unrelenting idea that photovoltaic energy is luxurious or costly. Quite the opposite, the previous few years showed that solar panels have turn out to be much more competent and efficient in offering a developed price and value relationship that roughly erase the gap of prices in relevant to grid.
In previous years, the financial aspect of this technology indicates a minimal disparity on bill cost for break even. For example, two-face cells collect the light that is reflected from the backside pane on the cell back side. The use of antireflective glass amd the dual antireflective coating augments the efficiency of solar cell further. The result for the high performance cells boosts the solar energy production and the economic return of the consumer.
For the other mentioned obstacle of the solar technology which is the doubt of future clients, the major cause of this problem is the conflicting political settings. Administrations have taken back their help for renewable energies as a whole. Thus, they also have taken their support for the photovoltaic technology in particular.
In Europe, there exist different speed and range in the business industry that influence the source of doubt for the future patrons of the technology. The support for this kind of industry was reduced by thirty percent in Germany. Financial support has been cut and ended for solar technology in Spain.
Assurance in the solar industry is declining even though the British administration too has abridged its feed-in tax financial support. This progress should be viewed as indication that the industry is currently strong enough to require less and less government assistance for its survival. There have been an unexpected number of photovoltaic modules installed over the previous years. People are aware of the need to change the energy source from fossil fuels to renewable energy sources as a hopeful power supply. Solar technology is both advantageous in cost-wise and environment-wise.
The future of photovoltaic and solar energy industry is very promising since the expansion of the market has been surprising. Solar power has been the principal supply of new-fangled electricity production for two successive years. The solar industry’s auxiliary development is achievable. The trade organization for the solar business called ‘The Solar Trade Association’ aspires to twice the quantity of domestic establishment, in United Kingdom, of solar panels to one meter. It was predicted to be obtained as soon as the year 2015. The prediction illustrates a good and established position of the market. Further consolidation consequential to cheaper solar panels and more competitive prices can be expected with the expansion of the market. Installation and module costs persist to decrease
The standard cost for a UK domestic installation of solar panels has by now approach cost around £7,000. Residence owners can accomplish a number of highly beneficial from investment of solar energy other than lower installation costs. The clients can obtain about eight percent return on their asset supplementary sustained by condensed energy bills and assisted through feed-in taxes for about twenty years.
Contemporary solar power systems by now create sufficient energy to control most residential electrical devices such as heat pumps and refrigerators. Benefits will still be elevated in terms of environment and monetary issues with cars that are electrically powered on the probable market perception.
Competition is as well going to be a significant aspect in the solar technology fuel production, improvement and expansion of the equipment. Supplementary consolidation in the business industry and competitiveness of the cost of solar panels will turn out to be a major constituent with regards to the future solar industry. Initially, corporations will need to propose viable costs for services and products to be able to be advance of the competition. Through the production of higher efficiency products in bigger consignments, costs will persist to decline in the long run attaining equivalence with retail electricity costs.
Storage of power will turn to be more and more vital through products forming the future of photovoltaic, higher return on investment an more affordable and innovative systems.
Power storage systems will consent to clientele to accomplish factual self-government using the grid. The storage of solar electricity systems permit clients to utilize their solar power precisely at time wanted. Storage is an imperative pace to approach an additional ground-breaking advancement on the marketplace. In accordance to Energy Post, the units for solar energy storage and the systems for smart photovoltaic will become several of the principal selling goods in the future.
The novel systems will be capable to make a decision whether they desire to operate separately from the grid or obtain association with an electronic brain. The implication is the power to choose if the new systems should be a self-generated power inside a closed circuit or if desirable, attach to the grid to purchase or vend electricity.
One of the founders of energy storage market is the German government. They began the new-fangled financial support to coerce the implementation of the storage for solar energy systems. The crossbreed arrangements allow consumers to stockpile and employ solar energy as desired. California has as well in progress for comparable method to fund housing energy storage and condense costs for storage structures. Forecast from research firm HIS states that the latest storage resolutions will facilitate clients to amplify their energy supply in the range of thirty to sixty percent.
There were 200,000 dispersed solar clienteles in the United States in the year 2011 base from the study of the Solar Electric Power Association (SEPA). Accordingly the major approaching danger to the efficacy representation corresponds to less than one percent of the market of the United States retail electricity. In 2013, seventy percent of the dispersed activity focused on the ten utilities. They converse to the augmented jeopardy owed to a diminutive position of businesses. The risk to the effectiveness model from unsettling factors is, at the present, progressively more practical because of a union of previous factors.
There is acceleration on the pressure to the central utility company representation because of: the decrease in the photovoltaic panels’ costs which are from $3.80/watt (in 2008) to $0.86/watt (in mid-2012). It is predicted that the costs of PV panels will not augment, or not amplify significantly, just as the present supply overload is determined at the same time as a quantity of supply will issue the cost-curve development sustainability. The exhausted cost of PV solar setting up is estimated to be $5/watt inclusive of the projection of the cost waning more as scale is taken in; a boost in rates of utility in such a way that the competitive cost prospect for photovoltaic solar is currently inside the business range for around sixteen percent of the retail electricity market of U.S. where charges are at or beyond $0.15/kWh .
Role of Solar Power in humanities near/long-term energy future
and its interaction to other energy technologies
Even in its formative years, research in photovoltaic solar cell has attained huge development in previous five years, with the competence level currently getting to ten percent. This situates a highlight for organic solar cell research in general. Considerable improvement can be projected for the upcoming steps for this hopeful field. The tandem idea unlocks a novel facet in materials of polymeric semiconductors plan. Additional developments in interrelated strata will be vital to sustain the technology to shift to actual everyday life submission. A lot of efficient methods made in solo junction polymer solar cells may be used in tandem arrangements too. Summarizing these techniques; those successful in enhancing exterior quantum effectiveness over an extensive spectral band are predominantly imperative.
In 2013, Japan’s Mitsubishi Chemicals has showed an approximately eighty percent EQE transversely in an expansive variety. The EQE of polymer tandem solar cells is within the 50% array. The positive EQE improvement contenders might encompass collecting and keeping of light by means of optical effects like the optical spacer and initiating the catching of light in plasmonic and nano-structures dynamic nanoparticles. Fifteen percent effectiveness in polymer tandem solar cells may possibly be managed with elevated EQE alone .
The tandem OPV is an incredibly optimistic investigation venue. There has been a fast progress undergone by diminutive molecule tandem solar cells. Approximately six percent efficiency was obtained in 2005 for tiny molecule tandem solar cells. In 2013, there is an efficiency equivalent to around ten percent in Germany using the tandem small molecule solar cells and this denotes a lofty probability of little molecule tandem solar cells. Seven percent efficiency was obtained from solution procedure of small molecules. A broad space for enhancement of solar cells solution processed tandem small molecule. For the previous ten years, OPV machinery has improved appreciably in both small molecule areas and polymer. They have solution that is evaporated and processed. The facts show adequate grounds to consider that the technological advances will incessant to appear, and the solar cells made of polymer tandem are especially optimistic for new-fangled boundary for OPV technology to understand the high efficiency and low cost assurance (Youa et al., 2013).
Conclusion
Photovoltaic technology is the production of electricity through the photon illumination of semiconductors . It is one of the most sustainable alternatives in terms of effectiveness; and a good electrical generation technology.
Some of the advantages of PV are the high reported efficiencies of conversion of solar to fuel energy; independent of the power-producing connection in reference to the official latent for the wanted reactions; no combustion that is beneficial to pollution and climate change; no discharges for the duration of operation; operates in ambient temperature that can prevent corrosion due to high temperature .
Photovoltaic (PV) has a noteworthy prospective amongst the unconventional energy generation because of the solar energy renewability, source of electricity and the PV-material portability .
The disadvantages and limitations related with PV-based cells are making a structure with the electrolyte-immersed operational photovoltaic cell; accomplishing a cost improvement for building electrolyte and catalysts interfaces that are steady conductive and transparent under fuel structuring operational setting; and forming a scheme that use a separate photovoltaic cell in dry setting connected to a distinct fuel-forming apparatus.
The current state of technological development of the solar power (photovoltaic technology) includes the development of other kinds of PV such as PV-biased electrosynthetic cells, photoelectrochemical PEC cells and regenerative photoelectrochemical cells. Photovoltaic cells, PV that generates electricity are called solar electric cells. On the other hand, the PV cells that create fuels are called PV-biased electrosynthetic cells. Photoelectrochemical PEC cells are devices that use solid/ionic-conductor junctions or solid/electrolyte junctions. Regenerative photoelectrochemical cells are PEC cells that generate electricity only. Photoelectrosynthetic cells are PEC cells that create fuels at the electrolyte-semiconductor junction. PEC-biased photoelectrosynthetic cell is the result when photoelectrosynthetic PEC cell is combined with a regenerative PEC cell.
Contemporary solar power systems create sufficient energy to control most residential electrical devices such as heat pumps and refrigerators. Benefits will still be elevated in terms of environment and monetary issues with cars that are electrically powered.
Future challenges in developing solar power (photovoltaic technology) include the presence of an elevated height of doubt amongst possible clientele for this technology. There is unrelenting idea that photovoltaic energy is luxurious or costly. The future of photovoltaic and solar energy industry is very promising. Solar power has been the principal supply of new-fangled electricity production for two successive years. The solar industry’s auxiliary development is achievable. The industrial and domestic patrons of solar technology choose to invest because the technology allows them to retract power from the providers of energy and to acquire more management over their prospect energy demand for payment.
Power storage systems will consent to clientele to accomplish factual self-government using the grid. The storage of solar electricity systems permit clients to utilize their solar power precisely at time wanted
Considerable improvement can be projected for the upcoming steps for this hopeful field. The tandem idea unlocks a novel facet in materials of polymeric semiconductors plan. Additional developments in interrelated strata will be vital to sustain the technology to shift to actual everyday life submission.
Further research is required for the electrodes stabilization using materials that serve as conductive and transparent defensive layers, the integration of components, detection of resources, maturity of low-cost manufacturing techniques and the building up of a photovoltaic cells that is cost competitive (Nielander et al., 2014).
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