Towards In-reduced photovoltaic absorbers: Evaluation of zinc-blende CuInSe2-ZnSe solid solution

- CuInSe2-ZnSe suitability for photovoltaic application has been investigated.
- Cu content has a strong effect on structural and electrical properties of CuInSe2-ZnSe.
- A 7.6% power conversion efficiency was obtained using CuInSe2-ZnSe as an absorber.

We have synthesized CuInSe2-ZnSe (CZISe) thin films by two-step sequential process and tested its potential for photovoltaic application. The material exhibits a high absorption coefficient (>105 cm−1 at wavelength lower than 800 nm) and a direct band gap around 1.2 eV, being an excellent candidate for absorber in thin film solar cells. The power and temperature dependent photoluminescence properties were similar to chalcopyrite and kesterite type materials. In a first optimization round, we have studied the influence of Cu content on the structural and electrical properties of CZISe. The optimum range of Cu/(Zn+In) ratio was identified that yielded the best performance of solar cells. The champion cell demonstrated an efficiency of 7.6% with an open circuit voltage as high as 520 mV, corroborating the possible high interest of this alloy for the development of sustainable, cost-efficient and critical raw materials reduced thin film photovoltaic technologies.