Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion

Abstract

Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base–emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions.

Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells

“…If the current density at the front base contact of the bottom cell J FB is negative, we emulate the BJT 3T tandem solar cell …”

“…In order to separate the minority carriers of each cell and to provide efficient majority carrier flow from the top into the bottom cell, minority carrier (hole) blocking layers or majority (electron) selective contact are necessary at the common base contact in the mid of the tandem cell.…”

“…If the current density at the front base contact of the bottom cell J FB is negative, we emulate the BJT 3T tandem solar cell. 41,54,55 The Figure 5D), instead of a coupling layer as in Figure 5A-C. For a n-type (p-type) base, a pn-n-np…”

“…The model introduced so far (with R IBC = 0 and R FB = 0) in Figure 6A is intuitive and therefore commonly used for mid-contacted 3T tandem solar cells, 25,28,34,35,39 as shown in Figure 6B,C (with R IBC = 0 and R FB = 0). The BJT solar cell, which has the same architecture as reported earlier by several authors, [25][26][27][28][29][30][31][32][33][34][35][36]41 was modeled by Martí and Luque using Ebers-Moll model 54 and turns out to be still describable by Figure 6C (without resistors). Figure 6B and 6C).…”

Computation of Electronic Energy Band Diagrams for Piezotronic Semiconductor and Electrochemical Systems

“…Recently, piezotronics have gained considerable popularity and significant progress in piezotronic tuning has found applications in catalysis, light-emitting diodes, nanorobotics, transistors, sensors and actuators, energy storage, and many energy harvesting and transduction technologies. [9][10][11][12][13][14][15][16][17][18][19][20] In most cases, the useful properties that emerge from these technologies depend strongly on the magnitude of the built-in and piezo-modified electric fields, length scale of the depletion Electronic energy band diagrams provide useful and illustrative information on how material stacking might affect electronic properties and charge transport throughout a multijunction device. However, schematic diagrams, which are often used in many publications, lack quantified changes in potential across junction interfaces.…”