Impact of piezoelectric polarization on the performance of InGaN/GaN p-i-n solar cells with Ga- and N-face polarity

To fully understand the role of spontaneous and piezoelectric polarization on carrier dynamics in InGaN/GaN solar cells, a p-GaN/i-InxGa1-xN/n-GaN double-heterostructure is being studied with the aim of improving its internal and external properties. Numerical simulations with reliable model parameters have been used to compare structures with N-face and Ga-face polarity. In order to include the effects of inelastic strain relaxation, when the compressively strained InGaN layers approach their critical thickness, we simulated the p-i-n InGaN structures by varying the piezoelectric field while keeping the spontaneous polarization unchanged. As strain relaxation leads to formation of non-radiative recombination centers, and critical thickness strongly depends on indium content, we also studied the dependency of device performance on indium fraction and non-radiative center density, allowing to identify the optimal device structure. The results clearly show that the sample with the N-face polarity in presence of piezoelectric fields reaches a good conversion efficiency and is less sensitive to strain relaxation compared to the metal polarity case. This type of research can lead to an optimization of the InGaN solar cell for further experimental implementation, holding great promise for thoroughly boosting the use of solar energy in the framework of the current energy revolution.

Automated summary

This study investigates the impact of spontaneous and piezoelectric polarization on carrier dynamics in InGaN/GaN solar cells. Numerical simulations comparing structures with N-face and Ga-face polarity were conducted. The optimal device structure was identified by studying the dependency of device performance on indium fraction and non-radiative center density.