Third generation photovoltaics: Ultra‐high conversion efficiency at low cost

Abstract

Since the early days of terrestrial photovoltaics, a common perception has been that ®rst generation' silicon wafer-based solar cells eventually would be replaced by à second generation' of lower cost thin-®lm technology, probably also involving a different semiconductor. Historically, cadmium sulphide, amorphous silicon, copper indium diselenide, cadmium telluride and now thin-®lm polycrystalline silicon have been regarded as key thin-®lm candidates. Any mature solar cell technology seems likely to evolve to the stage where costs are dominated by those of the constituent materials, be they silicon wafers or glass sheet. It is argued, therefore, that photovoltaics is likely to evolve, in its most mature form, to a`third generation' of high-ef®ciency thin-®lm technology. By high ef®ciency, what is meant is energy conversion values double or triple the 15±20% range presently targeted, closer to the thermodynamic limit of 93%. Tandem cells are the best known of such high-ef®ciency approaches, where ef®ciency can be increased merely by adding more cells of different bandgap to a cell stack, at the expense of increased complexity and spectral sensitivity. However, a range of other more`paralleled' approaches offer similar ef®ciency to an in®nite stack of tandem cells. These options are reviewed together with possible approaches for practical implementation, likely to become more feasible with the evolution of materials technology over the next two decades.

Transparent Conducting Polymer/Nitride Semiconductor Heterojunction Solar Cells

“…Therefore, a multilayer structure comprising a variety of bandgaps is effective for the collection of photons in a wide range of the solar spectrum. The current (2010) best research-cell efficiencies of typical solar cells are as follows (Green, 2010): crystalline Si (25.0%), multicrystalline Si (20.4%), crystalline GaAs (26.4%), CuInGaSe (19.4%), CdTe (16.7%), amorphous Si (10.1%), dye-sensitized polymers (10.4%), and organic polymers (5.15%). In addition to these, there have been a number of studies focused on developing "third-generation photovoltaics" with ultra-high conversion efficiencies at a low cost (Green, 2001).…”

“…The current (2010) best research-cell efficiencies of typical solar cells are as follows (Green, 2010): crystalline Si (25.0%), multicrystalline Si (20.4%), crystalline GaAs (26.4%), CuInGaSe (19.4%), CdTe (16.7%), amorphous Si (10.1%), dye-sensitized polymers (10.4%), and organic polymers (5.15%). In addition to these, there have been a number of studies focused on developing "third-generation photovoltaics" with ultra-high conversion efficiencies at a low cost (Green, 2001). More recently, after the discovery of the wide band gap range of 0.65-3.4 eV in In x Ga 1-x N, this material is considered to be one of the most promising candidates for third-generation photovoltaic cells.…”

Efficiency Improvement of P-I-N Solar Cell by Embedding Quantum Dots

“…Then, another photon with energy higher than the bandgap between the intermediate and the conduction bands pumps the previous electron to the conduction band [10]. By providing an additional intermediate band between the valence and the conduction bands, photon absorption has been made more efficient [7]. QD solar cell is one of the methods to implement IBSC's.…”

“…The quantum dots are embedded in a matrix to form an intermediate band, with its energy level dependent on the QD size. An alternative form of IBSC is the bulk IB solar cells, in which the intermediate bands are created with strongly mismatched alloys [11] or high concentration of impurities such as rare-earth elements [7] to create multiple intermediate bands.…”

“…Multi-junction solar cells [7,8] and light-concentrated solar cells [9] have been proposed to break the efficiency limit. The efficiency has been pushed to 37.9% with a three-layered solar cell, composed of InGaP/GaAs/InGaAs [6], and 44.4%, under 302 suns of concentration [6].…”