Reliability analysis of InGaN/GaN multi-quantum-well solar cells under thermal stress

Abstract

We investigate the thermal stability of InGaN solar cells under thermal stress at elevated temperatures from 400 °C to 500 °C. High Resolution X-Ray Diffraction analysis reveals that material quality of InGaN/GaN did not degrade after thermal stress. The external quantum efficiency characteristics of solar cells were well-maintained at all temperatures, which demonstrates the thermal robustness of InGaN materials. Analysis of current density–voltage (J–V) curves shows that the degradation of conversion efficiency of solar cells is mainly caused by the decrease in open-circuit voltage (Voc), while short-circuit current (Jsc) and fill factor remain almost constant. The decrease in Voc after thermal stress is attributed to the compromised metal contacts. Transmission line method results further confirmed that p-type contacts became Schottky-like after thermal stress. The Arrhenius model was employed to estimate the failure lifetime of InGaN solar cells at different temperatures. These results suggest that while InGaN solar cells have high thermal stability, the degradation in the metal contact could be the major limiting factor for these devices under high temperature operation.

High-Temperature Polarization-Free III-Nitride Solar Cells with Self-Cooling Effects

“…Ti/Al/Ni/Au and Ni/Au grid contacts deposited via electron beam evaporation were employed as n and p metal contacts, respectively. More structural and fabrication details on InGaN solar cells can be found in refs and .…”

“…The intrinsic PV conversion efficiency of these devices typically showed a sharp decrease with increasing temperatures; that is, these cells exhibit a negative temperature coefficient. , For example, GaAs solar cells were reported with an absolute efficiency drop of 0.4% per 10-degree temperature increase at one-sun and failed shortly after exposure to high temperature. , The escalating short-circuit current ( J sc ) and dropping open-circuit voltage ( V oc ) at high temperatures of these cells are also detrimental to the PV module operation. Furthermore, other extrinsic effects such as degradation in metal contacts further exacerbate the device performance at high temperature. − …”

“…Wide-bandgap III-nitride InGaN materials have emerged as a promising candidate for high-temperature solar cells. In x Ga 1– x N alloys have a tunable direct bandgap from ultraviolet (GaN ∼3.4 eV) to near-infrared (InN ∼0.7 eV) spectral regions derived by changing the In compositions that provide a perfect match to the solar spectrum. − Due to the relatively wider bandgap compared to Si or III–V, InGaN solar cells are also expected to have higher operation temperatures and superior radiation tolerance. , These properties therefore make them particularly suitable for aforementioned space missions and terrestrial PVT hybrid systems. Despite these advantageous properties, InGaN solar cells are still a nascent field in PV due to well-known challenges in III-nitrides such as high defect density due to lack of native substrates .…”

“…16−19 Due to the relatively wider bandgap compared to Si or III−V, InGaN solar cells are also expected to have higher operation temperatures and superior radiation tolerance. 15,17 These properties therefore make them particularly suitable for aforementioned space missions and terrestrial PVT hybrid systems. Despite these advantageous properties, InGaN solar cells are still a nascent field in PV due to well-known challenges in III-nitrides such as high defect density due to lack of native substrates.…”

Accurate Model for Temperature Dependence of Solar Cell Performance According to Phonon Energy Correction

“…Reliability is one of the important factors in the selection of solar cells besides their efficiency [5]. Solar cells that cannot survive in extreme environmental conditions will have an impact on increased maintenance costs that will increase the electricity price.…”