Guidelines and limitations for the design of high-efficiency InGaN single-junction solar cells

Abstract

Indium gallium nitride (InGaN) alloys offer great potential for high-efficiency photovoltaics, yet theoretical promise has not been experimentally demonstrated. Several major challenges remain including polarization effects, suitable p-type doping, improved surface passivation, and growth of thick, high-quality InGaN layers. In this paper, we present numerical simulations of InGaN p-in single-junction solar cells to provide guidelines for performance improvement through optimization of device structures given achievable material characteristics. The performance of both InGaN/GaN heterojunction devices that are presently achievable and InGaN homojunction solar cells that should be feasible in the future are investigated through the calculation of characteristic parameters: short-circuit current density, open-circuit voltage, and conversion efficiency. These simulations study the effect of indium content, thickness, and background doping of the unintentionally-doped InGaN absorbing layer on the performance of both InGaN solar-cell designs. While the maximum efficiency of a p-in InGaN/GaN heterojunction solar cell with low indium composition is 11.3%, the conversion efficiency of heterojunction devices with high indium composition needed for longer wavelength absorption drastically reduces because of polarization effects. Above an indium composition of 45%, the modeled heterojunction devices do not operate as solar cells. Using presently achievable values of minority carrier lifetime and surface recombination velocity, the maximum efficiency of InGaN single-homojunction solar cells with optimized parameters is ~17%, which is significantly smaller than the theoretical maximum energy-conversion efficiency for singlejunction cells.

Design and Simulation of InGaN/GaN p–i–n Photodiodes

“…The increase of the i‐layer thickness leads to increase the depletion width W , and therefore a higher saturation current density J o , which decreases the V oc . The photodiode works as a solar cell and the obtained behaviors of J sc and V oc are similar to what was found by simulating p–i–n InGaN/GaN solar cells . The responsivity as a function of wavelength for different absorbing i‐layer thickness is shown in Figure .…”

“…The photodiode works as a solar cell and the obtained behaviors of J sc and V oc are similar to what was found by simulating p-i-n InGaN/GaN solar cells. [26] The responsivity as a function of wavelength for different absorbing i-layer thickness is shown in Figure 8. It can be seen that the responsivity increased with the rise of thickness of the i-layer above the wavelength of 0.35 μm.…”

Numerical Study of InGaN based Photovoltaic by SCAPs Simulation

“…As the indium composition increases, this polarization-induced potential barrier becomes more prominent. The barrier height in the conduction band between the p-GaN and the n-In x Ga 1-x N layers increases when Indium content increases and the polarization-induced field that opposes drift transport increases [21][22][23] .…”

Development of Novel Thin Film Solar Cells: Design and Numerical Optimisation

“…InGaN has the potential to achieve high photovoltaic efficiency since its bandgap can cover the whole solar spectrum, as illustrated in Figure 1, by changing the indium composition. 5 In addition, this ternary alloy can potentially permit to fabricate cost effective and robust solar cells operating at high temperature and high light intensity, e.g., in concentrator solar cells. The main drawbacks of using this material are the difficulty to grow thin film with high indium composition, the difficulty of p-type doping and the realisation of ohmic contacts.…”